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Title: The Handbook of Soap Manufacture
Author: Appleton, H. A., Simmons, W. H.
Language: English
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Book Project.)



THE HANDBOOK OF

SOAP MANUFACTURE

BY

W. H. SIMMONS, B.Sc. (LOND.), F.C.S.

AND

H. A. APPLETON

_WITH TWENTY-SEVEN ILLUSTRATIONS_

LONDON
SCOTT, GREENWOOD & SON
"THE OIL AND COLOUR TRADES JOURNAL" OFFICES
8 BROADWAY, LUDGATE HILL, E.C.
1908
[_All rights reserved_]

Transcriber's note:

For text: A word surrounded by a cedilla such as ~this~ signifies that
the word is bolded in the text. A word surrounded by underscores like
_this_ signifies the word is italics in the text. Greek letters
are translated into English and are in brackets, e.g. [alpha].

For numbers and equations: Parentheses have been added to clarify
fractions. Underscores before bracketed numbers/letters in equations
denote a subscript.

Footnotes have been moved to the end of the chapter and minor typos have
been corrected.



PREFACE


In the general advance of technical knowledge and research during the
last decade, the Soap Industry has not remained stationary. While there
has not perhaps been anything of a very revolutionary character, steady
progress has still been made in practically all branches, and the aim of
the present work is to describe the manufacture of Household and Toilet
Soaps as carried out to-day in an up-to-date and well-equipped factory.

In the more scientific portions of the book, an acquaintance with the
principles of elementary chemistry is assumed, and in this we feel
justified, as in these days of strenuous competition, no soap-maker can
hope to compete successfully with his rivals unless he has a sound
theoretical as well as practical knowledge of the nature of the raw
materials he uses, and the reactions taking place in the pan, or at
other stages of the manufacture. We also venture to hope that the work
may prove useful to Works' Chemists and other Analysts consulted in
connection with this Industry.

At the same time, in the greater part of the book no chemical knowledge
is necessary, the subject being treated in such a way that it is hoped
those who are not directly engaged in the manufacture of soap, but who
desire a general idea of the subject, will find it of value.

In the sections dealing with the composition and analysis of materials,
temperatures are expressed in degrees Centigrade, these being now almost
invariably used in scientific work. In the rest of the book, however,
they are given in degrees Fahrenheit (the degrees Centigrade being also
added in brackets), as in the majority of factories these are still
used.

As regards strengths of solution, in some factories the use of Baumé
degrees is preferred, whilst in others Twaddell degrees are the custom,
and we have therefore given the two figures in all cases.

In the chapter dealing with Oils and Fats, their Saponification
Equivalents are given in preference to Saponification Values, as it has
been our practice for some years to express our results in this way, as
suggested by Allen in _Commercial Organic Analysis_, and all our
records, from which most of the figures for the chief oils and fats are
taken, are so stated.

For the illustrations, the authors are indebted to Messrs. E. Forshaw &
Son, Ltd., H. D. Morgan, and W. J. Fraser & Co., Ltd.

W. H. S.
H. A. A.

LONDON, _September_, 1908.



CONTENTS


                                                                       PAGE

CHAPTER I.

INTRODUCTION.                                                             1

Definition of Soap--Properties--Hydrolysis--Detergent Action.


CHAPTER II.

CONSTITUTION OF OILS AND FATS, AND THEIR SAPONIFICATION                   6

Researches of Chevreul and Berthelot--Mixed Glycerides--Modern Theories
of Saponification--Hydrolysis accelerated by (1) HEAT OR ELECTRICITY,
(2) FERMENTS, Castor-seed Ferment, Steapsin, Emulsin, and (3) CHEMICAL
REAGENTS, Sulphuric Acid, Twitchell's Reagent, Hydrochloric Acid, Lime,
Magnesia, Zinc Oxide, Soda and Potash.


CHAPTER III.

RAW MATERIALS USED IN SOAP-MAKING                                        24

Fats and Oils--Waste Fats--Fatty Acids--Less-known Oils and Fats of Limited
Use--Various New Fats and Oils Suggested for Soap-making--Rosin--Alkali
(Caustic and Carbonated)--Water--Salt--Soap-stock.


CHAPTER IV.

BLEACHING AND TREATMENT OF RAW MATERIALS INTENDED FOR
  SOAP-MAKING                                                            41

Palm Oil--Cotton-seed Oil--Cotton-seed "Foots"--Vegetable Oils--Animal
Fats--Bone Fat--Rosin.


CHAPTER V.

SOAP-MAKING                                                              45

Classification of Soaps--Direct combination of Fatty Acids with
Alkali--Cold Process Soaps--Saponification under Increased or Diminished
Pressure--Soft Soap--Marine Soap--Hydrated Soaps, Smooth and
Marbled--Pasting or Saponification--Graining Out--Boiling on
Strength--Fitting--Curd Soaps--Curd Mottled--Blue and Grey Mottled
Soaps--Milling Base--Yellow Household Soaps--Resting of Pans and
Settling of Soap--Utilisation of Nigres--Transparent soaps--Saponifying
Mineral Oil--Electrical Production of Soap.


CHAPTER VI.

TREATMENT OF SETTLED SOAP                                                60

Cleansing--Crutching--Liquoring of Soaps--Filling--Neutralising,
Colouring and Perfuming--Disinfectant
Soaps--Framing--Slabbing--Barring--Open and Close
Piling--Drying--Stamping--Cooling.


CHAPTER VII.

TOILET, TEXTILE AND MISCELLANEOUS SOAPS                                  77

Toilet Soaps--Cold Process soaps--Settled Boiled Soaps--Remelted
Soaps--Milled Soaps--Drying--Milling and Incorporating Colour, Perfume,
or Medicament--Perfume--Colouring matter--Neutralising and Superfatting
Material--Compressing--Cutting--Stamping--Medicated Soaps--Ether
Soap--Floating Soaps--Shaving Soaps--Textile Soaps--Soaps for Woollen,
Cotton and Silk Industries--Patent Textile Soaps--Miscellaneous Soaps.


CHAPTER VIII.

SOAP PERFUMES                                                            95

Essential Oils--Source and Preparation--Properties--Artificial and
Synthetic Perfumes.


CHAPTER IX.

GLYCERINE MANUFACTURE AND PURIFICATION                                  111

Treatment of Lyes--Evaporation to Crude
Glycerine--Distillation--Distilled and Dynamite Glycerine--Chemically
Pure Glycerine--Animal Charcoal for Decolorisation--Glycerine obtained
by other methods of Saponification--Yield of Glycerine from Fats and
Oils.


CHAPTER X.

ANALYSIS OF RAW MATERIALS, SOAP, AND GLYCERINE                          117

Fats and Oils--Alkalies and Alkali Salts--Essential Oils--Soap--Lyes--Crude
Glycerine.


CHAPTER XI.

STATISTICS OF THE SOAP INDUSTRY                                         140


APPENDIX A.

COMPARISON OF DEGREES, TWADDELL AND BAUMÉ, WITH ACTUAL DENSITIES        147


APPENDIX B.

COMPARISON OF DIFFERENT THERMOMETRIC SCALES                             148


APPENDIX C.

TABLE OF THE SPECIFIC GRAVITIES OF SOLUTIONS OF CAUSTIC SODA            149


APPENDIX D.

TABLE OF STRENGTH OF CAUSTIC POTASH SOLUTIONS AT 60° F.                 151


INDEX                                                                   153



CHAPTER I.

INTRODUCTION.

     _Definition of Soap--Properties--Hydrolysis--Detergent Action._


It has been said that the use of soap is a gauge of the civilisation of
a nation, but though this may perhaps be in a great measure correct at
the present day, the use of soap has not always been co-existent with
civilisation, for according to Pliny (_Nat. Hist._, xxviii., 12, 51)
soap was first introduced into Rome from Germany, having been discovered
by the Gauls, who used the product obtained by mixing goats' tallow and
beech ash for giving a bright hue to the hair. In West Central Africa,
moreover, the natives, especially the Fanti race, have been accustomed
to wash themselves with soap prepared by mixing crude palm oil and water
with the ashes of banana and plantain skins. The manufacture of soap
seems to have flourished during the eighth century in Italy and Spain,
and was introduced into France some five hundred years later, when
factories were established at Marseilles for the manufacture of
olive-oil soap. Soap does not appear to have been made in England until
the fourteenth century, and the first record of soap manufacture in
London is in 1524. From this time till the beginning of the nineteenth
century the manufacture of soap developed very slowly, being essentially
carried on by rule-of-thumb methods, but the classic researches of
Chevreul on the constitution of fats at once placed the industry upon a
scientific basis, and stimulated by Leblanc's discovery of a process for
the commercial manufacture of caustic soda from common salt, the
production of soap has advanced by leaps and bounds until it is now one
of the most important of British industries.

_Definition of Soap_.--The word soap (Latin _sapo_, which is cognate
with Latin _sebum_, tallow) appears to have been originally applied to
the product obtained by treating tallow with ashes. In its strictly
chemical sense it refers to combinations of fatty acids with metallic
bases, a definition which includes not only sodium stearate, oleate and
palmitate, which form the bulk of the soaps of commerce, but also the
linoleates of lead, manganese, etc., used as driers, and various
pharmaceutical preparations, _e.g._, mercury oleate (_Hydrargyri
oleatum_), zinc oleate and lead plaster, together with a number of other
metallic salts of fatty acids. Technically speaking, however, the
meaning of the term soap is considerably restricted, being generally
limited to the combinations of fatty acids and alkalies, obtained by
treating various animal or vegetable fatty matters, or the fatty acids
derived therefrom, with soda or potash, the former giving hard soaps,
the latter soft soaps.

The use of ammonia as an alkali for soap-making purposes has often been
attempted, but owing to the ease with which the resultant soap is
decomposed, it can scarcely be looked upon as a product of much
commercial value.

H. Jackson has, however, recently patented (Eng. Pat. 6,712, 1906) the
use of ammonium oleate for laundry work. This detergent is prepared in
the wash-tub at the time of use, and it is claimed that goods are
cleansed by merely immersing them in this solution for a short time and
rinsing in fresh water.

Neither of the definitions given above includes the sodium and potassium
salts of rosin, commonly called rosin soap, for the acid constituents of
rosin have been shown to be aromatic, but in view of the analogous
properties of these resinates to true soap, they are generally regarded
as legitimate constituents of soap, having been used in Great Britain
since 1827, and receiving legislative sanction in Holland in 1875.

Other definitions of soap have been given, based not upon its
composition, but upon its properties, among which may be mentioned that
of Kingzett, who says that "Soap, considered commercially, is a body
which on treatment with water liberates alkali," and that of Nuttall,
who defines soap as "an alkaline or unctuous substance used in washing
and cleansing".

_Properties of Soap._--Both soda and potash soaps are readily soluble in
either alcohol or hot water. In cold water they dissolve more slowly,
and owing to slight decomposition, due to hydrolysis (_vide infra_), the
solution becomes distinctly turbid. Sodium oleate is peculiar in not
undergoing hydrolysis except in very dilute solution and at a low
temperature. On cooling a hot soap solution, a jelly of more or less
firm consistence results, a property possessed by colloidal bodies, such
as starch and gelatine, in contradistinction to substances which under
the same conditions deposit crystals, due to diminished solubility of
the salt at a lower temperature.

Krafft (_Journ. Soc. Chem. Ind._, 1896, 206, 601; 1899, 691; and 1902,
1301) and his collaborators, Wiglow, Strutz and Funcke, have
investigated this property of soap solutions very fully, the researches
extending over several years. In the light of their more recent work,
the molecules, or definite aggregates of molecules, of solutions which
become gelatinous on cooling move much more slowly than the molecules in
the formation of a crystal, but there is a definite structure, although
arranged differently to that of a crystal. In the case of soda soaps the
colloidal character increases with the molecular weight of the fatty
acids.

Soda soaps are insoluble in concentrated caustic lyes, and, for the most
part, in strong solutions of sodium chloride, hence the addition of
caustic soda or brine to a solution of soda soap causes the soap to
separate out and rise to the surface. Addition of brine to a solution of
potash soap, on the other hand, merely results in double decomposition,
soda soap and potassium chloride being formed, thus:--

    C_{17}H_{35}COOK + NaCl   =  C_{17}H_{35}COONa + KCl
      potassium       sodium       sodium          potassium
      stearate       chloride     stearate         chloride

The solubility of the different soaps in salt solution varies very
considerably. Whilst sodium stearate is insoluble in a 5 per cent.
solution of sodium chloride, sodium laurate requires a 17 per cent.
solution to precipitate it, and sodium caproate is not thrown out of
solution even by a saturated solution.

_Hydrolysis of Soap_.--The term "hydrolysis" is applied to any
resolution of a body into its constituents where the decomposition is
brought about by the action of water, hence when soap is treated with
_cold_ water, it is said to undergo hydrolysis, the reaction taking
place being represented in its simplest form by the equation:--

    2NaC_{18}H_{35}O_{2} + H_{2}O  =  NaOH +   HNa(C_{18}H_{35}O_{2})_{2}
    sodium                  water    caustic      acid sodium
    stearate                         soda         stearate

The actual reaction which occurs has been the subject of investigation
by many chemists, and very diverse conclusions have been arrived at.
Chevreul, the pioneer in the modern chemistry of oils and fats, found
that a small amount of alkali was liberated, as appears in the above
equation, together with the formation of an acid salt, a very minute
quantity of free fatty acid remaining in solution. Rotondi (_Journ. Soc.
Chem. Ind._, 1885, 601), on the other hand, considered that a neutral
soap, on being dissolved in water, was resolved into a basic and an acid
salt, the former readily soluble in both hot and cold water, the latter
insoluble in cold water, and only slightly soluble in hot water. He
appears, however, to have been misled by the fact that sodium oleate is
readily soluble in cold water, and his views have been shown to be
incorrect by Krafft and Stern (_Ber. d. Chem. Ges._, 1894, 1747 and
1755), who from experiments with pure sodium palmitate and stearate
entirely confirm the conclusions arrived at by Chevreul.

The extent of dissociation occurring when a soap is dissolved in water
depends upon the nature of the fatty acids from which the soap is made,
and also on the concentration of the solution. The sodium salts of
cocoa-nut fatty acids (capric, caproic and caprylic acids) are by far
the most easily hydrolysed, those of oleic acid and the fatty acids from
cotton-seed oil being dissociated more readily than those of stearic
acid and tallow fatty acids. The decomposition increases with the amount
of water employed.

The hydrolytic action of water on soap is affected very considerably by
the presence of certain substances dissolved in the water, particularly
salts of calcium and magnesium. Caustic soda exerts a marked retarding
effect on the hydrolysis, as do also ethyl and amyl alcohols and
glycerol.

_Detergent Action of Soap._--The property possessed by soap of removing
dirt is one which it is difficult to satisfactorily explain. Many
theories, more or less complicated, have been suggested, but even now
the question cannot be regarded as solved.

The explanation commonly accepted is that the alkali liberated by
hydrolysis attacks any greasy matter on the surface to be cleansed, and,
as the fat is dissolved, the particles of dirt are loosened and easily
washed off. Berzelius held this view, and considered that the value of a
soap depended upon the ease with which it yielded free alkali on
solution in water.

This theory is considered by Hillyer (_Journ. Amer. Chem. Soc._, 1903,
524), however, to be quite illogical, for, as he points out, the
liberated alkali would be far more likely to recombine with the acid or
acid salt from which it has been separated, than to saponify a neutral
glyceride, while, further, unsaponifiable greasy matter is removed by
soap as easily as saponifiable fat, and there can be no question of any
chemical action of the free alkali in its case. Yet another argument
against the theory is that hydrolysis is greater in cold and dilute
solutions, whereas hot concentrated soap solutions are generally
regarded as having the best detergent action.

Rotondi (_Journ. Soc. Chem. Ind._, 1885, 601) was of the opinion that
the basic soap, which he believed to be formed by hydrolysis, was alone
responsible for the detergent action of soap, this basic soap dissolving
fatty matter by saponification, but, as already pointed out, his theory
of the formation of a basic soap is now known to be incorrect, and his
conclusions are therefore invalid.

Several explanations have been suggested, based on the purely physical
properties of soap solutions. Most of these are probably, at any rate in
part, correct, and there can be little doubt that the ultimate solution
of the problem lies in this direction, and that the detergent action of
soap will be found to depend on many of these properties, together with
other factors not yet known.

Jevons in 1878 in some researches on the "Brownian movement" or
"pedesis" of small particles, a movement of the particles which is
observed to take place when clay, iron oxide, or other finely divided
insoluble matter is suspended in water, found that the pedetic action
was considerably increased by soap and sodium silicate, and suggested
that to this action of soap might be attributed much of its cleansing
power.

Alder Wright considered that the alkali liberated by hydrolysis in some
way promoted contact of the water with the substance to be cleansed, and
Knapp regarded the property of soap solutions themselves to facilitate
contact of the water with the dirt, as one of the chief causes of the
efficacy of soap as a detergent.

Another way in which it has been suggested that soap acts as a cleanser
is that the soap itself or the alkali set free by hydrolysis serves as a
lubricant, making the dirt less adherent, and thus promoting its
removal.

The most likely theory yet advanced is that based on the emulsifying
power of soap solutions. The fact that these will readily form emulsions
with oils has long been known, and the detergent action of soap has
frequently been attributed to it, the explanation given being that the
alkali set free by the water emulsifies the fatty matter always adhering
to dirt, and carries it away in suspension with the other impurities.
Experiments by Hillyer (_loc. cit._) show, however, that while N/10
solution of alkali will readily emulsify a cotton-seed oil containing
free acidity, no emulsion is produced with an oil from which all the
acidity has been removed, or with kerosene, whereas a N/10 solution of
sodium oleate will readily give an emulsion with either, thus proving
that the emulsification is due to the soap itself, and not to the
alkali.

Plateau (_Pogg. Ann._, 141, 44) and Quincke (_Wiedmann's. Ann._, 35,
592) have made very complete researches on the emulsification and
foaming of liquids and on the formation of bubbles. The former considers
that there are two properties of a liquid which play an important part
in the phenomenon, (1) it must have considerable viscosity, and (2) its
surface tension must be low. Quincke holds similar views, but considers
that no pure liquid will foam.

Soap solution admirably fulfils Plateau's second condition, its surface
tension being only about 40 per cent. of that of water, while its
cohesion is also very small; and it is doubtless to this property that
its emulsifying power is chiefly due. So far as viscosity is concerned,
this can have but little influence, for a 1 per cent. solution of sodium
oleate, which has a viscosity very little different from that of pure
water, is an excellent emulsifying agent.

Hillyer, to whose work reference has already been made, investigated the
whole question of detergent action very exhaustively, and, as the result
of a very large number of experiments, concludes that the cleansing
power of soap is largely or entirely to be explained by the power which
it has of emulsifying oily substances, of wetting and penetrating into
oily textures, and of lubricating texture and impurities so that these
may be removed easily. It is thought that all these properties may be
explained by taking into account the low cohesion of the soap solutions,
and their strong attraction or affinity to oily matter, which together
cause the low surface tension between soap solution and oil.



CHAPTER II.

CONSTITUTION OF OILS AND FATS, AND THEIR SAPONIFICATION.

     _Researches of Chevreul and Berthelot--Mixed Glycerides--Modern
     Theories of Saponification--Hydrolysis accelerated by (1) Heat
     or Electricity, (2) Ferments; Castor-seed Ferment, Steapsin,
     Emulsin, and (3) Chemical Reagents; Sulphuric Acid, Twitchell's
     Reagent, Hydrochloric Acid, Lime, Magnesia, Zinc Oxide, Soda
     and Potash._


The term oil is of very wide significance, being applied to substances
of vastly different natures, both organic and inorganic, but so far as
soap-making materials are concerned, it may be restricted almost
entirely to the products derived from animal and vegetable sources,
though many attempts have been made during the last few years to also
utilise mineral oils for the preparation of soap. Fats readily become
oils on heating beyond their melting points, and may be regarded as
frozen oils.

Although Scheele in 1779 discovered that in the preparation of lead
plaster glycerol is liberated, soap at that time was regarded as a mere
mechanical mixture, and the constitution of oils and fats was not
properly understood. It was Chevreul who showed that the manufacture of
soap involved a definite chemical decomposition of the oil or fat into
fatty acid and glycerol, the fatty acid combining with soda, potash, or
other base, to form the soap, and the glycerol remaining free. The
reactions with stearin and palmitin (of which tallow chiefly consists)
and with olein (found largely in olive and cotton-seed oils) are as
follows:--

          CH_{2}OOC_{18}H_{35}                             CH_{2}OH
          |                                                |
          CHOOC_{18}H_{35} + 3NaOH = 3NaOOC_{18}H_{35} +   CHOH
          |                                                |
          CH_{2}OOC_{18}H_{35}                             CH_{2}OH

            stearin         sodium       sodium            glycerol
                           hydroxide     stearate


          CH_{2}OOC_{16}H_{31}                             CH_{2}OH
          |                                                |
          CHOOC_{16}H_{31} + 3NaOH = 3NaOOC_{16}H_{31} +   CHOH
          |                                                |
          CH_{2}OOC_{16}H_{31}                             CH_{2}OH

             palmitin        sodium      sodium            glycerol
                            hydroxide    palmitate

          CH_{2}OOC_{18}H_{33}                           CH_{2}OH
          |                                              |
          CHOOC_{18}H_{33} + 3NaOH = 3NaOOC_{18}H_{33} + CHOH
          |                                              |
          CH_{2}OOC_{18}H_{33}                           CH_{2}OH

          olein              sodium    sodium            glycerol
                            hydroxide  oleate

Berthelot subsequently confirmed Chevreul's investigations by directly
synthesising the fats from fatty acids and glycerol, the method he
adopted consisting in heating the fatty acids with glycerol in sealed
tubes. Thus, for example:--

  3C_{18}H_{35}O_{2}H + C_{3}H_{5}(OH)_{3} = C_{3}H_{5}(C_{18}H_{35}O_{2})_{3}
  stearic acid           glycerol              tristearin

Since glycerol is a trihydric alcohol, _i.e._, contains three hydroxyl
(OH) groups, the hydrogen atoms of which are displaceable by acid
radicles, the above reaction may be supposed to take place in three
stages. Thus, we may have:--

    (1) C_{18}H_{35}O_{2}H + C_{3}H_{5}(OH)_{3} =
           C_{3}H_{5}(OH)_{2}C_{18}H_{35}O_{2} + H_{2}O
                                            monostearin

    (2) C_{18}H_{35}O_{2}H + C_{3}H_{5}(OH)_{2}C_{18}H_{35}O_{2} =
           C_{3}H_{5}(OH)(C_{18}H_{35}O_{2})_{2} + H_{2}O
                                            distearin

    (3) C_{18}H_{35}O_{2}H + C_{3}H_{5}(OH)(C_{18}H_{35}O_{2})_{2} =
           C_{3}H_{5}(C_{18}H_{35}O_{2})_{3} + H_{2}O
                                            tristearin

There are two possible forms of monoglyceride and diglyceride, according
to the relative position of the acid radicle, these being termed alpha
and beta respectively, and represented by the following formulæ, where R
denotes the acid radicle:--

_Monoglyceride_:--

                   CH_{2}OR                     CH_{2}OH
                   |                            |
          (alpha)  CHOH           and (beta)    CHOR
                   |                            |
                   CH_{2}OH                     CH_{2}OH

_Diglyceride_:--

                   CH_{2}OR                     CH_{2}OR
                   |                            |
          (alpha)  CHOH           and (beta)    CHOR
                   |                            |
                   CH_{2}OR                     CH_{2}OH

According to the relative proportions of fatty acid and glycerol used,
and the temperature to which they were heated, Berthelot succeeded in
preparing mono-, di- and triglycerides of various fatty acids.

Practically all the oils and fats used in soap-making consist of
mixtures of these compounds of glycerol with fatty acids, which
invariably occur in nature in the form of triglycerides.

It was formerly considered that the three acid radicles in any naturally
occurring glyceride were identical, corresponding to the formula--

          CH_{2}OR
          |
          CHOR
          |
          CH_{2}OR

where R denotes the acid radicle. Recent work, however, has shown the
existence of several so-called _mixed glycerides_, in which the
hydroxyls of the same molecule of glycerol are displaced by two or
sometimes three different acid radicles.

The first mixed glyceride to be discovered was oleodistearin,
C_{3}H_{5}(OC_{18}H_{35}O)(OC_{18}H_{35}O)_{2}, obtained by Heise in 1896
Mkani fat. Hansen has since found that tallow contains oleodipalmitin,
from C_{3}H_{5}(OC_{18}H_{35}O)(OC_{16}H_{31}O), stearodipalmitin,
C_{3}H_{5}(OC_{18}H_{35}O)(OC_{16}H_{31}O), oleopalmitostearin,
C_{3}H_{5}(OC_{18}H_{33}O)(OC_{16}H_{31}O)(OC_{18}H_{35}O) and
palmitodistearin, CH(OC_{16}H_{31}O)(OC_{18}H_{35}O)_{2}, the latter of
which has also been obtained by Kreis and Hafner from lard, while Holde
and Stange have shown that olive oil contains from 1 to 2 per cent. of
oleodidaturin, C_{3}H_{5}(OC_{18}H_{33}O)(OC_{17}H_{33}O)_{2}, and
Hehner and Mitchell have obtained indications of mixed glycerides in
linseed oil (which they consider contains a compound of glycerol with
two radicles of linolenic acid and one radicle of oleic acid), also in
cod-liver, cod, whale and shark oils.

In some cases the fatty acids are combined with other bases than
glycerol. As examples may be cited beeswax, containing myricin or
myricyl palmitate, and spermaceti, consisting chiefly of cetin or cetyl
palmitate, and herein lies the essential difference between fats and
waxes, but as these substances are not soap-making materials, though
sometimes admixed with soap to accomplish some special object, they do
not require further consideration.

The principal pure triglycerides, with their formulæ and chief
constants, are given in the following table:--

[Transcriber's note: Table split to fit on page better.]

---------------------------------------------------------------------
Glyceride. |          Formula.                   | Chief Occurrence.
---------------------------------------------------------------------
Butyrin    | C_{3}H_{5}(O.C_{4}H_{7}O)_{3}       |   Butter fat
---------------------------------------------------------------------
Isovalerin | C_{3}H_{5}(O.C_{5}H_{9}O)_{3}       |  Porpoise, dolphin
---------------------------------------------------------------------
Caproin    | C_{3}H_{5}(O.C_{6}H_{11}O)_{3}      |   Cocoa-nut and
           |                                     |    palm-nut oils
---------------------------------------------------------------------
Caprylin   | C_{3}H_{5}(O.C_{8}H_{15}O)_{3}      |     Do. do.
---------------------------------------------------------------------
Caprin     | C_{3}H_{5}(O.C_{10}H_{19}O)_{3}     |     Do.  do.
---------------------------------------------------------------------
Laurin     | C_{3}H_{5}(O.C_{12}H_{23}O)_{3}     |     Do.  do.
---------------------------------------------------------------------
Myristin   | C_{3}H_{5}(O.C_{14}H_{27}O)_{3}     |   Nutmeg butter
---------------------------------------------------------------------
Palmitin   | C_{3}H_{5}(O.C_{16}H_{31}O)_{3}     |   Palm oil, lard
---------------------------------------------------------------------
Stearin    | C_{3}H_{5}(O.C_{18}H_{35}O)_{3}     |   Tallow, lard,
           |                                     |   cacao butter
---------------------------------------------------------------------
Olein      | C_{3}H_{5}(O.C_{18}H_{33}O)_{3}     |   Olive and
           |                                     |   almond oils
---------------------------------------------------------------------
Ricinolein | C_{3}H_{5}(O.C_{18}H_{33}O_{2})_{3} |   Castor oil
---------------------------------------------------------------------

---------------------------------------------------------------------
Glyceride.  |   Melting         | Refractive       |  Saponification
            |  Point, °C.       | Index at 60° C.  |    Equivalent.
---------------------------------------------------------------------
Butyrin     |  Liquid at -60    |   1.42015        |     100.7
---------------------------------------------------------------------
Isovalerin  |   ...             |     ...          |     114.7
---------------------------------------------------------------------
Caproin     |   -25             |   1.42715        |     128.7
---------------------------------------------------------------------
Caprylin    |   -8.3            |   1.43316        |     156.7
---------------------------------------------------------------------
Caprin      |    31.1           |   1.43697        |     184.7
---------------------------------------------------------------------
Laurin      |    45             |   1.44039        |     212.7
---------------------------------------------------------------------
Myristin    |    56.5           |   1.44285        |     240.7
---------------------------------------------------------------------
Palmitin    |    63-64          |     ...          |     268.7
---------------------------------------------------------------------
Stearin     |    71.6           |     ...          |     296.7
---------------------------------------------------------------------
Olein       |  Solidifies at -6 |   ...            |     294.7
---------------------------------------------------------------------
Ricinolein  |      ...          |   ...            |     310.7
---------------------------------------------------------------------

Of the above the most important from a soap-maker's point of view are
stearin, palmitin, olein and laurin, as these predominate in the fats
and oils generally used in that industry. The presence of stearin and
palmitin, which are solid at the ordinary temperature, gives firmness to
a fat; the greater the percentage present, the harder the fat and the
higher will be the melting point, hence tallows and palm oils are solid,
firm fats. Where olein, which is liquid, is the chief constituent, we
have softer fats, such as lard, and liquid oils, as almond, olive and
cotton-seed.

_Stearin_ (Tristearin) can be prepared from tallow by crystallisation
from a solution in ether, forming small crystals which have a bright
pearly lustre. The melting point of stearin appears to undergo changes
and suggests the existence of distinct modifications. When heated to 55°
C. stearin liquefies; with increase of temperature it becomes solid, and
again becomes liquid at 71.6° C. If this liquid be further heated to 76°
C., and allowed to cool, it will not solidify until 55° C. is reached,
but if the liquid at 71.6° C. be allowed to cool, solidification will
occur at 70° C.

_Palmitin_ (Tripalmitin) may be obtained by heating together palmitic
acid and glycerol, repeatedly boiling the resulting product with strong
alcohol, and allowing it to crystallise. Palmitin exists in scales,
which have a peculiar pearly appearance, and are greasy to the touch.
After melting and solidifying, palmitin shows no crystalline fracture;
when heated to 46° C. it melts to a liquid which becomes solid on
further heating, again liquefying when 61.7° C. is reached, and becoming
cloudy, with separation of crystalline particles. At 63° C. it is quite
clear, and this temperature is taken as the true melting point. It has
been suggested that the different changes at the temperatures mentioned
are due to varying manipulation, such as rate at which the temperature
is raised, and the initial temperature of the mass when previously cool.

_Olein_ (Triolein) is an odourless, colourless, tasteless oil, which
rapidly absorbs oxygen and becomes rancid. It has been prepared
synthetically by heating glycerol and oleic acid together, and may be
obtained by submitting olive oil to a low temperature for several days,
when the liquid portion may be further deprived of any traces of stearin
and palmitin by dissolving in alcohol. Olein may be distilled _in vacuo_
without decomposition taking place.

_Laurin_ (Trilaurin) may be prepared synthetically from glycerol and
lauric acid. It crystallises in needles, melting at 45°-46° C., which
are readily soluble in ether, but only slightly so in cold absolute
alcohol. Scheij gives its specific gravity, _d_60°/4° = 0.8944. Laurin
is the chief constituent of palm-kernel oil, and also one of the
principal components of cocoa-nut oil.

_Fatty Acids._--When a fat or oil is saponified with soda or potash, the
resulting soap dissolved in hot water, and sufficient dilute sulphuric
acid added to decompose the soap, an oily layer gradually rises to the
surface of the liquid, which, after clarifying by warming and washing
free from mineral acid, is soluble in alcohol and reddens blue litmus
paper. This oily layer consists of the "fatty acids" or rather those
insoluble in water, acids like acetic, propionic, butyric, caproic,
caprylic and capric, which are all more or less readily soluble in
water, remaining for the most part dissolved in the aqueous portion. All
the acids naturally present in oils and fats, whether free or combined,
are monobasic in character, that is to say, contain only one
carboxyl--CO.OH group. The more important fatty acids may be classified
according to their chemical constitution into five homologous series,
having the general formulæ:--

            I. Stearic series     C_{n}H_{2n+1}COOH
           II. Oleic series       C_{n}H_{2n-1}COOH
          III. Linolic series     C_{n}H_{2n-3}COOH
           IV. Linolenic series   C_{n}H_{2n-5}COOH
            V. Ricinoleic series  C_{n}H_{2n-7}COOH

I. _Stearic Series._--The principal acids of this series, together with
their melting points and chief sources, are given in the following
table:--

-------------------------------------------------------------------------------
Acid.          | Formula.          | Melting | Found in
               |                   | Point,  |
               |                   | °C.     |
-------------------------------------------------------------------------------
Acetic         | CH_{3}COOH        | 17      | Macassar oil.
------------------------------------------------------------------------------
Butyric        | C_{3}H_{7}COOH    |  ...    | Butter, Macassar oil.
------------------------------------------------------------------------------
Isovaleric     | C_{4}H_{9}COOH    |  ...    | Porpoise and dolphin oils.
------------------------------------------------------------------------------
Caproic        | C_{5}H_{11}COOH   |  ...    | Butter, cocoa-nut oil.
------------------------------------------------------------------------------
Caprylic       | C_{7}H_{15}COOH   | 15      | Butter, cocoa-nut oil,
               |                   |         | Limburg cheese.
------------------------------------------------------------------------------
Capric         | C_{9}H_{19}COOH   | 30      | Butter, cocoa-nut oil.
------------------------------------------------------------------------------
Lauric         | C_{11}H_{23}COOH  | 44      | Cocoa-nut oil, palm-kernel oil.
------------------------------------------------------------------------------
Ficocerylic    | C_{12}H_{25}COOH  |   ...   | Pisang wax.
------------------------------------------------------------------------------
Myristic       | C_{13}H_{27}COOH  | 54      | Nutmeg butter, liver fat,
               |                   |         | cocoa-nut oil, dika fat,
               |                   |         | croton oil.
------------------------------------------------------------------------------
Palmitic       | C_{15}H_{31}COOH  | 62.5    | Palm oil, most animal fats.
------------------------------------------------------------------------------
Daturic        | C_{16}H_{33}COOH  |         | Oil of Datura Stramonium.
------------------------------------------------------------------------------
Stearic        | C_{17}H_{35}COOH  | 69      | Tallow, lard, most solid
               |                   |         | animal fats.
------------------------------------------------------------------------------
Arachidic      | C_{19}H_{39}COOH  | 75      | Arachis or earth-nut oil,
               |                   |         | rape and mustard-seed oils.
------------------------------------------------------------------------------
Behenic        | C_{21}H_{43}COOH  |  ...    | Ben oil, black mustard-seed
               |                   |         | oil, rape oil.
------------------------------------------------------------------------------
Lignoceric     | C_{23}H_{47}COOH  | 80.5    | Arachis oil.
------------------------------------------------------------------------------
Carnaubic      | C_{23}H_{47}COOH  |  ...    | Carnauba wax.
------------------------------------------------------------------------------
Pisangcerylic  | C_{23}H_{47}COOH  |  ...    | Pisang wax.
------------------------------------------------------------------------------
Hyænic         | C_{24}H_{49}COOH  |  ...    | Hyæna fat.
------------------------------------------------------------------------------
Cerotic        | C_{25}H_{51}COOH  | 78      | Beeswax, China wax, spermaceti.
------------------------------------------------------------------------------
Melissic       | C_{29}H_{59}COOH  | 89      | Beeswax.
------------------------------------------------------------------------------
Psyllostearylic| C_{32}H_{65}COOH  |  ...    | Psylla wax.
------------------------------------------------------------------------------
Theobromic     | C_{63}H_{127}COOH |  ...    | Cacao butter
------------------------------------------------------------------------------

Medullic and margaric acids, which were formerly included in this
series, have now been shown to consist of mixtures of stearic and
palmitic, and stearic palmitic and oleic acids respectively.

The acids of this group are saturated compounds, and will not combine
directly with iodine or bromine. The two first are liquid at ordinary
temperatures, distil without decomposition, and are miscible with water
in all proportions; the next four are more or less soluble in water and
distil unchanged in the presence of water, as does also lauric acid,
which is almost insoluble in cold water, and only slightly dissolved by
boiling water. The higher acids of the series are solid, and are
completely insoluble in water. All these acids are soluble in warm
alcohol, and on being heated with solid caustic alkali undergo no
change.

II. _Oleic Series:_--

--------------------------------------------------------------------------
Acid.       | Formula.          | Melting |   Found in
            |                   | Point,  |
            |                   | °C.     |
--------------------------------------------------------------------------
Tiglic      | C_{4}H_{7}COOH    | 64.5    |   Croton oil.
--------------------------------------------------------------------------
Moringic    | C_{14}H_{27}COOH  |  0      |   Ben oil.
--------------------------------------------------------------------------
Physetoleic | C_{15}H_{29}COOH  | 30      |   Sperm oil.
--------------------------------------------------------------------------
Hypogæic    | C_{15}H_{29}COOH  | 33      |   Arachis and maize oils.
--------------------------------------------------------------------------
Oleic       | C_{17}H_{33}COOH  | 14      |   Most oils and fats.
--------------------------------------------------------------------------
Rapic       | C_{17}H_{33}COOH  | ...     |   Rape oil.
--------------------------------------------------------------------------
Doeglic     | C_{18}H_{35}COOH  | ...     |   Bottle-nose oil.
--------------------------------------------------------------------------
Erucic      | C_{21}H_{41}COOH  | 34      |   Mustard oils, marine animal
            |                   |         |     oils, rape oil.
--------------------------------------------------------------------------

The unsaturated nature of these acids renders their behaviour with
various reagents entirely different from that of the preceding series.
Thus, they readily combine with bromine or iodine to form addition
compounds, and the lower members of the series are at once reduced, on
treatment with sodium amalgam in alkaline solution, to the corresponding
saturated acids of Series I. Unfortunately, this reaction does not apply
to the higher acids such as oleic acid, but as the conversion of the
latter into solid acids is a matter of some technical importance from
the point of view of the candle-maker, a number of attempts have been
made to effect this by other methods.

De Wilde and Reychler have shown that by heating oleic acid with 1 per
cent. of iodine in autoclaves up to 270°-280° C., about 70 per cent. is
converted into stearic acid, and Zürer has devised (German Patent
62,407) a process whereby the oleic acid is first converted by the
action of chlorine into the dichloride, which is then reduced with
nascent hydrogen. More recently Norman has secured a patent (English
Patent 1,515, 1903) for the conversion of unsaturated fatty acids of
Series II. into the saturated compounds of Series I., by reduction with
hydrogen or water-gas in the presence of finely divided nickel, cobalt
or iron. It is claimed that by this method oleic acid is completely
transformed into stearic acid, and that the melting point of tallow
fatty acids is raised thereby about 12° C.

Another method which has been proposed is to run the liquid olein over
a series of electrically charged plates, which effects its reduction to
stearin.

Stearic acid is also formed by treating oleic acid with fuming hydriodic
acid in the presence of phosphorus, while other solid acids are obtained
by the action of sulphuric acid or zinc chloride on oleic acid.

Acids of Series II. may also be converted into saturated acids by
heating to 300°C. with solid caustic potash, which decomposes them into
acids of the stearic series with liberation of hydrogen. This reaction,
with oleic acid, for example, is generally represented by the equation--

  C_{18}H_{34}O_{2} + 2KOH = KC_{2}H_{3}O_{2} + KC_{16}H_{31}O_{2} + H_{2},

though it must be really more complex than this indicates, for, as Edmed
has pointed out, oxalic acid is also formed in considerable quantity.
The process on a commercial scale has now been abandoned.

One of the most important properties of this group of acids is the
formation of isomeric acids of higher melting point on treatment with
nitrous acid, generally termed the _elaidin reaction_. Oleic acid, for
example, acted upon by nitrous acid, yields elaidic acid, melting at
45°, and erucic acid gives brassic acid, melting at 60°C. This reaction
also occurs with the neutral glycerides of these acids, olein being
converted into elaidin, which melts at 32°C.

The lead salts of the acids of this series are much more soluble in
ether, and the lithium salts more soluble in alcohol than those of the
stearic series, upon both of which properties processes have been based
for the separation of the solid from the liquid fatty acids.

III. _Linolic Series:_--

--------------------------------------------------------------------------
Acid.        |  Formula.        | Melting    | Found in
             |                  | Point,     |
             |                  | °C.        |
--------------------------------------------------------------------------
Elæomargaric | C_{16}H_{29}COOH |  ...       |  Chinese-wood oil.
--------------------------------------------------------------------------
Elæostearic  | C_{16}H_{29}COOH |  71        |  Chinese-wood oil.
--------------------------------------------------------------------------
Linolic      | C_{17}H_{31}COOH |  Fluid     |  Linseed, cotton-seed and
             |                  |            |  maize oils.
--------------------------------------------------------------------------
Tariric      | C_{17}H_{31}COOH |  50.5      |  Tariri-seed oil.
--------------------------------------------------------------------------
Telfairic    | C_{17}H_{31}COOH |  Fluid     |  Telfairia oil.
--------------------------------------------------------------------------

These acids readily combine with bromine, iodine, or oxygen. They are
unaffected by nitrous acid, and their lead salts are soluble in ether.

IV. _Linolenic Series:_--

--------------------------------------------------------------------
Acid.        |  Formula.         | Found in
--------------------------------------------------------------------
Linolenic    |  C_{17}H_{29}COOH | Linseed oil.
--------------------------------------------------------------------
Isolinolenic |  C_{17}H_{29}COOH | Linseed oil.
--------------------------------------------------------------------
Jecoric      |  C_{17}H_{29}COOH | Cod-liver and marine animal oils.
--------------------------------------------------------------------

These acids are similar in properties to those of Class III., but
combine with six atoms of bromine or iodine, whereas the latter combine
with only four atoms.

V. _Ricinoleic Series:_--

 -----------------------------------------------------------
|            |                      |         |             |
|    Acid.   |        Formula.      | Melting |  Found in   |
|            |                      |  Point, |             |
|            |                      |   °C.   |             |
|------------|----------------------|---------|-------------|
|            |                      |         |             |
| Ricinoleic | C_{17}H_{22}(OH)COOH |   4-5   | Castor oil. |
 -----------------------------------------------------------

This acid combines with two atoms of bromine or iodine, and is converted
by nitrous acid into the isomeric ricinelaidic acid, which melts at
52°-53° C. Pure ricinoleic acid, obtained from castor oil, is optically
active, its rotation being [alpha]_{d} +6° 25'.

_Hydrolysis or Saponification of Oils and Fats._--The decomposition of a
triglyceride, brought about by caustic alkalies in the formation of
soap, though generally represented by the equation already given (pp. 6
and 7)--

    C_{3}H_{5}(OR) + 3NaOH = C_{3}H_{5}(OH)_{3} + 3RONa,

is not by any means such a simple reaction.

In the first place, though in this equation no water appears, the
presence of the latter is found to be indispensable for saponification
to take place; in fact, the water must be regarded as actually
decomposing the oil or fat, caustic soda or potash merely acting as a
catalytic agent. Further, since in the glycerides there are three acid
radicles to be separated from glycerol, their saponification can be
supposed to take place in three successive stages, which are the
converse of the formation of mono- and diglycerides in the synthesis of
triglycerides from fatty acids and glycerine. Thus, the above equation
may be regarded as a summary of the following three:--

                           _                        _
                          | OR                     | OH
          (i.) C_{3}H_{5} | OR + NaOH = C_{3}H_{5} | OR + RONa
                          |_OR                     |_OR
                            _                        _
                           | OH                     | OH
          (ii.) C_{3}H_{5} | OR + NaOH = C_{3}H_{5} | OR + RONa
                           |_OR                     |_OH
                             _                        _
                            | OH                     | OH
          (iii.) C_{3}H_{5} | OR + NaOH = C_{3}H_{5} | OH + RONa
                            |_OH                     |_OH

Geitel and Lewkowitsch, who have studied this question from the physical
and chemical point of view respectively, are of opinion that when an
oil or fat is saponified, these three reactions do actually occur side
by side, the soap-pan containing at the same time unsaponified
triglyceride, diglyceride, monoglyceride, glycerol and soap.

This theory is not accepted, however, by all investigators. Balbiano and
Marcusson doubt the validity of Lewkowitsch's conclusions, and Fanto,
experimenting on the saponification of olive oil with caustic potash, is
unable to detect the intermediate formation of any mono- or diglyceride,
and concludes that in homogeneous solution the saponification is
practically quadrimolecular. Kreeman, on the other hand, from
physico-chemical data, supports the view of Geitel and Lewkowitsch that
saponification is bimolecular, and though the evidence seems to favour
this theory, the matter cannot be regarded as yet definitely settled.

Hydrolysis can be brought about by water alone, if sufficient time is
allowed, but as the process is extremely slow, it is customary in
practice to accelerate the reaction by the use of various methods, which
include (i.) the application of heat or electricity, (ii.) action of
enzymes, and (iii.) treatment with chemicals; the accelerating effect of
the two latter methods is due to their emulsifying power.

The most usual method adopted in the manufacture of soap is to hydrolyse
the fat or oil by caustic soda or potash, the fatty acids liberated at
the same time combining with the catalyst, _i.e._, soda or potash, to
form soap. Hitherto the other processes of hydrolysis have been employed
chiefly for the preparation of material for candles, for which purpose
complete separation of the glycerol in the first hydrolysis is not
essential, since the fatty matter is usually subjected to a second
treatment with sulphuric acid to increase the proportion of solid fatty
acids. The colour of the resulting fatty acids is also of no importance,
as they are always subjected to distillation.

During the last few years, however, there has been a growing attempt to
first separate the glycerol from the fatty acids, and then convert the
latter into soap by treatment with the carbonates of soda or potash,
which are of course considerably cheaper than the caustic alkalies, but
cannot be used in the actual saponification of a neutral fat. The two
processes chiefly used for this purpose are those in which the reaction
is brought about by enzymes or by Twitchell's reagent.

I. _Application of Heat or Electricity._--Up to temperatures of 150° C.
the effect of water on oils and fats is very slight, but by passing
superheated steam through fatty matter heated to 200°-300° C. the
neutral glycerides are completely decomposed into glycerol and fatty
acids according to the equation--

    C_{3}H_{5}(OR)_{3} + 3H.OH = C_{3}H_{5}(OH)_{3} + 3ROH.

The fatty acids and glycerol formed distil over with the excess of
steam, and by arranging a series of condensers, the former, which
condense first, are obtained almost alone in the earlier ones, and an
aqueous solution of glycerine in the later ones. This method of
preparation of fatty acids is extensively used in France for the
production of stearine for candle-manufacture, but the resulting
product is liable to be dark coloured, and to yield a dark soap. To
expose the acids to heat for a minimum of time, and so prevent
discoloration, Mannig has patented (Germ. Pat. 160,111) a process
whereby steam under a pressure of 8 to 10 atmospheres is projected
against a baffle plate mounted in a closed vessel, where it mixes with
the fat or oil in the form of a spray, the rate of hydrolysis being
thereby, it is claimed, much increased.

Simpson (Fr. Pat. 364,587) has attempted to accelerate further the
decomposition by subjecting oils or fats to the simultaneous action of
heat and electricity. Superheated steam is passed into the oil, in which
are immersed the two electrodes connected with a dynamo or battery, the
temperature not being allowed to exceed 270° C.

II. _Action of Enzymes._--It was discovered by Muntz in 1871 (_Annales
de Chemie_, xxii.) that during germination of castor seeds a quantity of
fatty acid was developed in the seeds, which he suggested might be due
to the decomposition of the oil by the embryo acting as a ferment.
Schutzenberger in 1876 showed that when castor seeds are steeped in
water, fatty acids and glycerol are liberated, and attributed this to
the hydrolytic action of an enzyme present in the seeds. No evidence of
the existence of such a ferment was adduced, however, till 1890, when
Green (_Roy. Soc. Proc._, 48, 370) definitely proved the presence in the
seeds of a ferment capable of splitting up the oil into fatty acid and
glycerol.

The first experimenters to suggest any industrial application of this
enzymic hydrolysis were Connstein, Hoyer and Wartenburg, who
(_Berichte_, 1902, 35, pp. 3988-4006) published the results of a lengthy
investigation of the whole subject. They found that tallow, cotton-seed,
palm, olive, almond, and many other oils, were readily hydrolysed by the
castor-seed ferment in the presence of dilute acid, but that cocoa-nut
and palm-kernel oils only decomposed with difficulty. The presence of
acidity is essential for the hydrolysis to take place, the most suitable
strength being one-tenth normal, and the degree of hydrolysis is
proportional to the quantity of ferment present. Sulphuric, phosphoric,
acetic or butyric acids, or sodium bisulphate, may be used without much
influence on the result. Butyric acid is stated to be the best, but in
practice is too expensive, and acetic acid is usually adopted. The
emulsified mixture should be allowed to stand for twenty-four hours, and
the temperature should not exceed 40° C.; at 50° C. the action is
weakened, and at 100° C. ceases altogether.

Several investigators have since examined the hydrolysing power of
various other seeds, notably Braun and Behrendt (_Berichte_, 1903, 36,
1142-1145, 1900-1901, and 3003-3005), who, in addition to confirming
Connstein, Hoyer and Wartenburg's work with castor seeds, have made
similar experiments with jequirity seeds (_Abrus peccatorius_)
containing the enzyme abrin, emulsin from crushed almonds, the leaves of
_Arctostaphylos Uva Ursi_, containing the glucoside arbutin, myrosin
from black mustard-seed, gold lac (_Cheirantus cheiri_) and crotin from
croton seeds. Jequirity seeds were found to have a stronger decomposing
action on lanoline and carnauba wax than the castor seed, but only
caused decomposition of castor oil after the initial acidity was first
neutralised with alkali. Neither emulsin, arbutin nor crotin have any
marked hydrolytic action on castor oil, but myrosin is about half as
active as castor seeds, except in the presence of potassium myronate,
when no decomposition occurs.

S. Fokin (_J. russ. phys. chem. Ges._, 35, 831-835, and _Chem. Rev.
Fett. u. Harz. Ind._, 1904, 30 _et seq._) has examined the hydrolytic
action of a large number of Russian seeds, belonging to some thirty
different families, but although more than half of these brought about
the hydrolysis of over 10 per cent. of fat, he considers that in only
two cases, _viz._, the seeds of _Chelidonium majus_ and _Linaria
vulgaris_, is the action due to enzymes, these being the only two seeds
for which the yield of fatty acids is proportional to the amount of seed
employed, while in many instances hydrolysis was not produced when the
seeds were old. The seeds of _Chelidonium majus_ were found to have as
great, and possibly greater, enzymic activity than castor seeds, but
those of _Linaria_ are much weaker, twenty to thirty parts having only
the same lipolytic activity as four to five parts of castor seeds.

The high percentage of free acids found in rice oil has led C. A. Brown,
jun. (_Journ. Amer. Chem. Soc._, 1903, 25, 948-954), to examine the rice
bran, which proves to have considerable enzymic activity, and rapidly
effects the hydrolysis of glycerides.

The process for the utilisation of enzymic hydrolysis in the separation
of fatty acids from glycerine on the industrial scale, as originally
devised by Connstein and his collaborators, consisted in rubbing a
quantity of the coarsely crushed castor seeds with part of the oil or
fat, then adding the rest of the oil, together with acidified water
(N/10 acetic acid). The quantities employed were 6-1/2 parts of
decorticated castor beans for every 100 parts of oil or fat, and 50 to
60 parts of acetic acid. After stirring until an emulsion is formed, the
mixture is allowed to stand for twenty-four hours, during which
hydrolysis takes place. The temperature is then raised to 70°-80° C.,
which destroys the enzyme, and a 25 per cent. solution of sulphuric
acid, equal in amount to one-fiftieth of the total quantity of fat
originally taken, added to promote separation of the fatty acids. In
this way three layers are formed, the one at the top consisting of the
clear fatty acids, the middle one an emulsion containing portions of the
seeds, fatty acids and glycerine, and the bottom one consisting of the
aqueous glycerine. The intermediate layer is difficult to treat
satisfactorily; it is generally washed twice with water, the washings
being added to glycerine water, and the fatty mixture saponified and the
resultant soap utilised.

The process has been the subject of a considerable amount of
investigation, numerous attempts having been made to actually separate
the active fat-splitting constituent of the seeds, or to obtain it in a
purer and more concentrated form than is furnished by the seeds
themselves. Nicloux (_Comptes Rendus_, 1904, 1112, and _Roy. Soc.
Proc._, 1906, 77 B, 454) has shown that the hydrolytic activity of
castor seeds is due entirely to the cytoplasm, which it is possible to
separate by mechanical means from the aleurone grains and all other
cellular matter. This active substance, which he terms "lipaseidine," is
considered to be not an enzyme, though it acts as such, following the
ordinary laws of enzyme action; its activity is destroyed by contact
with water in the absence of oil. This observer has patented (Eng. Pat.
8,304, 1904) the preparation of an "extract" by triturating crushed
castor or other seeds with castor oil, filtering the oily extract, and
subjecting it to centrifugal force. The deposit consists of aleurone and
the active enzymic substance, together with about 80 per cent. of oil,
and one part of it will effect nearly complete hydrolysis of 100 parts
of oil in twenty-four hours. In a subsequent addition to this patent,
the active agent is separated from the aleurone by extraction with
benzene and centrifugal force. By the use of such an extract, the
quantity of albuminoids brought into contact with the fat is reduced to
about 10 per cent. of that in the original seeds, and the middle layer
between the glycerine solution and fatty acids is smaller and can be
saponified directly for the production of curd soap, while the glycerine
solution also is purer.

In a further patent Nicloux (Fr. Pat. 349,213, 1904) states that the use
of an acid medium is unnecessary, and claims that even better results
are obtained by employing a neutral solution of calcium sulphate
containing a small amount of magnesium sulphate, the proportion of salts
not exceeding 0.5 per cent. of the fat, while in yet another patent,
jointly with Urbain (Fr. Pat. 349,942, 1904), it is claimed that the
process is accelerated by the removal of acids from the oil or fat to be
treated, which may be accomplished by either washing first with
acidulated water, then with pure water, or preferably by neutralising
with carbonate of soda and removing the resulting soap.

Lombard (Fr. Pat. 350,179, 1904) claims that acids act as stimulating
agents in the enzymic hydrolysis of oils, and further that a simple
method of obtaining the active product is to triturate oil cake with its
own weight of water, allow the mixture to undergo spontaneous
proteolytic hydrolysis at 40° C. for eight days, and then filter, the
filtrate obtained being used in place of water in the enzymic process.

Hoyer, who has made a large number of experiments in the attempt to
isolate the lipolytic substance from castor seeds, has obtained a
product of great activity, which he terms "ferment-oil," by extracting
the crushed seeds with a solvent for oils.

The Verein Chem. Werke have extended their original patent (addition
dated 11th December, 1905, to Fr. Pat. 328,101, Oct., 1902), which now
covers the use of vegetable ferments in the presence of water and
manganese sulphate or other metallic salt. It is further stated that
acetic acid may be added at the beginning of the operation, or use may
be made of that formed during the process, though in the latter case
hydrolysis is somewhat slower.

Experiments have been carried out by Lewkowitsch and Macleod (_Journ.
Soc. Chem. Ind._, 1903, 68, and _Proc. Roy. Soc._, 1903, 31) with
ferments derived from animal sources, _viz._, lipase from pig's liver,
and steapsin from the pig or ox pancreas. The former, although it has
been shown by Kastle and Loevenhart (_Amer. Chem. Journ._, 1900, 49) to
readily hydrolyse ethyl butyrate, is found to have very little
fat-splitting power, but with steapsin more favourable results have been
obtained, though the yield of fatty acids in this case is considerably
inferior to that given by castor seeds. With cotton-seed oil, 83-86 per
cent. of fatty acids were liberated as a maximum after fifty-six days,
but with lard only 46 per cent. were produced in the same time. Addition
of dilute acid or alkali appeared to exert no influence on the
decomposition of the cotton-seed oil, but in the case of the lard,
dilute alkali seemed at first to promote hydrolysis, though afterwards
to retard it.

Fokin (_Chem. Rev. Fett. u. Harz. Ind._, 1904, 118-120 _et seq._) has
attempted to utilise the pancreatic juice on a technical scale, but the
process proved too slow and too costly to have any practical use.

_Rancidity._--The hydrolysing power of enzymes throws a good deal of
light on the development of rancidity in oils and fats, which is now
generally regarded as due to the oxidation by air in the presence of
light and moisture of the free fatty acids contained by the oil or fat.
It has long been known that whilst recently rendered animal fats are
comparatively free from acidity, freshly prepared vegetable oils
invariably contain small quantities of free fatty acid, and there can be
no doubt that this must be attributed to the action of enzymes contained
in the seeds or fruit from which the oils are expressed, hence the
necessity for separating oils and fats from adhering albuminous matters
as quickly as possible.

_Decomposition of Fats by Bacteria._--Though this subject is not of any
practical interest in the preparation of fatty acids for soap-making, it
may be mentioned, in passing, that some bacteria readily hydrolyse fats.
Schriber (_Arch. f. Hyg._, 41, 328-347) has shown that in the presence
of air many bacteria promote hydrolysis, under favourable conditions as
to temperature and access of oxygen, the process going beyond the simple
splitting up into fatty acid and glycerol, carbon dioxide and water
being formed. Under anærobic conditions, however, only a slight primary
hydrolysis was found to take place, though according to Rideal (_Journ.
Soc. Chem. Ind._, 1903, 69) there is a distinct increase in the amount
of free fatty acids in a sewage after passage through a septic tank.

Experiments have also been made on this subject by Rahn (_Centralb.
Bakteriol_, 1905, 422), who finds that _Penicillium glaucum_ and other
penicillia have considerable action on fats, attacking the glycerol and
lower fatty acids, though not oleic acid. A motile bacillus, producing
a green fluorescent colouring matter, but not identified, had a marked
hydrolytic action and decomposed oleic acid. The name "lipobacter" has
been proposed by De Kruyff for bacteria which hydrolyse fats.

III. _Use of Chemical Reagents._--Among the chief accelerators employed
in the hydrolysis of oils are sulphuric acid and Twitchell's reagent
(benzene- or naphthalene-stearosulphonic acid), while experiments have
also been made with hydrochloric acid (_Journ. Soc. Chem. Ind._, 1903,
67) with fairly satisfactory results, and the use of sulphurous acid, or
an alkaline bisulphite as catalyst, has been patented in Germany. To
this class belong also the bases, lime, magnesia, zinc oxide, ammonia,
soda and potash, though these latter substances differ from the former
in that they subsequently combine with the fatty acids liberated to form
soaps.

_Sulphuric Acid._--The hydrolysing action of concentrated sulphuric acid
upon oils and fats has been known since the latter part of the
eighteenth century, but was not applied on a practical scale till 1840
when Gwynne patented a process in which sulphuric acid was used to
liberate the fatty acids, the latter being subsequently purified by
steam distillation. By this method, sulpho-compounds of the glyceride
are first formed, which readily emulsify with water, and, on treatment
with steam, liberate fatty acids, the glycerol remaining partly in the
form of glycero-sulphuric acid. The process has been investigated by
Fremy, Geitel, and more recently by Lewkowitsch (_J. Soc. of Arts_,
"Cantor Lectures," 1904, 795 _et seq._), who has conducted a series of
experiments on the hydrolysis of tallow with 4 per cent. of sulphuric
acid of varying strengths, containing from 58 to 90 per cent. sulphuric
acid, H_{2}SO_{4}. Acid of 60 per cent. or less appears to be
practically useless as a hydrolysing agent, while with 70 per cent. acid
only 47.7 per cent. fatty acids were developed after twenty-two hours'
steaming, and with 80 and 85 per cent. acid, the maximum of 89.9 per
cent. of fatty acids was only reached after fourteen and fifteen hours'
steaming respectively. Using 98 per cent. acid, 93 per cent. of fatty
acids were obtained after nine hours' steaming, and after another seven
hours, only 0.6 per cent. more fatty acids were produced. Further
experiments have shown that dilute sulphuric acid has also scarcely any
action on cotton-seed, whale, and rape oils.

According to Lant Carpenter, some 75 per cent. of solid fatty acids may
be obtained from tallow by the sulphuric acid process, owing to the
conversion of a considerable quantity of oleic acid into isoleic acid
(_vide_ p. 12), but in the process a considerable proportion of black
pitch is obtained. C. Dreymann has recently patented (Eng. Pat. 10,466,
1904) two processes whereby the production of any large amount of
hydrocarbons is obviated. In the one case, after saponification with
sulphuric acid, the liberated fatty acids are washed with water and
treated with an oxide, carbonate, or other acid-fixing body, _e.g._,
sodium carbonate, prior to distillation. In this way the distillate is
much clearer than by the ordinary process, and is almost odourless,
while the amount of unsaponifiable matter is only about 1.2 per cent.
The second method claimed consists in the conversion of the fatty acids
into their methyl esters by treatment with methyl alcohol and
hydrochloric acid gas, and purification of the esters by steam
distillation, the pure esters being subsequently decomposed with
superheated steam, in an autoclave, with or without the addition of an
oxide, _e.g._, 0.1 per cent. zinc oxide, to facilitate their
decomposition.

_Twitchell's Reagent._--In Twitchell's process use is made of the
important discovery that aqueous solutions of fatty aromatic sulphuric
acids, such as benzene- or naphthalene-stearosulphonic acid, readily
dissolve fatty bodies, thereby facilitating their dissociation into
fatty acids and glycerol. These compounds are stable at 100° C., and are
prepared by treating a mixture of benzene or naphthalene and oleic acid
with an excess of sulphuric acid, the following reaction taking place:--

    C_{6}H_{6} + C_{18}H_{34}O_{2} + H_{2}SO_{4} =
        C_{6}H_{4}(SO_{3}H)C_{18}H_{35}O + H_{2}O.

On boiling the resultant product with water two layers separate, the
lower one consisting of a clear aqueous solution of sulphuric acid and
whatever benzene-sulphonic acid has been formed, while the upper layer,
which is a viscous oil, contains the benzene-stearosulphonic acid. This,
after washing first with hydrochloric acid and then rapidly with
petroleum ether, and drying at 100° C. is then ready for use; the
addition of a small quantity of this reagent to a mixture of fat
(previously purified) and water, agitated by boiling with open steam,
effects almost complete separation of the fatty acid from glycerol.

The process is generally carried out in two wooden vats, covered with
closely fitting lids, furnished with the necessary draw-off cocks, the
first vat containing a lead coil and the other a brass steam coil.

In the first vat, the fat or oil is prepared by boiling with 1 or 2 per
cent. of sulphuric acid (141° Tw. or 60° B.) for one or two hours and
allowed to rest, preferably overnight; by this treatment the fat is
deprived of any dirt, lime or other impurity present. After withdrawing
the acid liquor, the fat or oil is transferred to the other vat, where
it is mixed with one-fifth of its bulk of water (condensed or
distilled), and open steam applied. As soon as boiling takes place, the
requisite amount of reagent is washed into the vat by the aid of a
little hot water through a glass funnel, and the whole is boiled
continuously for twelve or even twenty-four hours, until the free fatty
acids amount to 85-90 per cent. The amount of reagent used varies with
the grade of material, the smaller the amount consistent with efficient
results, the better the colour of the finished product; with good
material, from 1/2 to 3/4 per cent. is sufficient, but for materials of
lower grade proportionately more up to 2 per cent. is required. The
reaction appears to proceed better with materials containing a fair
quantity of free acidity.

When the process has proceeded sufficiently far, the boiling is stopped
and free steam allowed to fill the vat to obviate any discoloration of
the fatty acids by contact with the air, whilst the contents of the vat
settle.

The settled glycerine water, which should amount in bulk to 50 or 60 per
cent. of the fatty matter taken, and have a density of 7-1/2° Tw. (5°
B.), is removed to a receptacle for subsequent neutralisation with milk
of lime, and, after the separation of sludge, is ready for
concentration.

The fatty acids remaining in the vat are boiled with a small quantity
(0.05 per cent., or 1/10 of the Twitchell reagent requisite) of
commercial barium carbonate, previously mixed with a little water; the
boiling may be prolonged twenty or thirty minutes, and at the end of
that period the contents of the vat are allowed to rest; the water
separated should be neutral to methyl-orange indicator.

It is claimed that fatty acids so treated are not affected by the air,
and may be stored in wooden packages.

_Hydrochloric Acid._--Lewkowitsch (_Journ. Soc. Chem. Ind._, 1903, 67)
has carried out a number of experiments on the accelerating influence of
hydrochloric acid upon the hydrolysis of oils and fats, which show that
acid of a specific gravity of 1.16 has a very marked effect on most
oils, cocoa-nut, cotton-seed, whale and rape oils, tallow and lard being
broken up into fatty acid and glycerol to the extent of some 82-96 per
cent. after boiling 100 grams of the oil or fat with 100 c.c. of acid
for twenty-four hours. The maximum amount of hydrolysis was attained
with cocoa-nut oil, probably owing to its large proportion of the
glycerides of volatile fatty acids. Castor oil is abnormal in only
undergoing about 20 per cent. hydrolysis, but this is attributed to the
different constitution of its fatty acids, and the ready formation of
polymerisation products. Experiments were also made as to whether the
addition of other catalytic agents aided the action of the hydrochloric
acid; mercury, copper sulphate, mercury oxide, zinc, zinc dust,
aluminium chloride, nitrobenzene and aniline being tried, in the
proportion of 1 per cent. The experiments were made on neutral lard and
lard containing 5 per cent. of free fatty acids, but in no case was any
appreciable effect produced.

So far this process has not been adopted on the practical scale, its
chief drawback being the length of time required for saponification.
Undoubtedly the hydrolysis would be greatly facilitated if the oil and
acid could be made to form a satisfactory emulsion, but although saponin
has been tried for the purpose, no means of attaining this object has
yet been devised.

_Sulphurous Acid or Bisulphite._--The use of these substances has been
patented by Stein, Berge and De Roubaix (Germ. Pat. 61,329), the fat
being heated in contact with the reagent for about nine hours at
175°-180° C. under a pressure of some 18 atmospheres, but the process
does not appear to be of any considerable importance.

_Lime._--The use of lime for the saponification of oils and fats was
first adopted on the technical scale for the production of candle-making
material, by De Milly in 1831. The insoluble lime soap formed is
decomposed by sulphuric acid, and the fatty acids steam distilled.

The amount of lime theoretically necessary to hydrolyse a given quantity
of a triglyceride, ignoring for the moment any catalytic influence, can
be readily calculated; thus with stearin the reaction may be represented
by the equation:--

     CH_{2}OOC_{18}H_{35}                                        CH_{2}OH
     |                                                           |
    2CHOOC_{18}H_{35} + 3Ca(OH)_{2} = 3Ca(OOC_{18}H_{35})_{2} + 2CHOH
     |                                                           |
     CH_{2}OOC_{18}H_{35}                                        CH_{2}OH
      stearin           milk of lime    calcium stearate         glycerol

In this instance, since the molecular weight of stearin is 890 and that
of milk of lime is 74, it is at once apparent that for every 1,780 parts
of stearin, 222 parts of milk of lime or 168 parts of quick-lime, CaO,
would be required. It is found in practice, however, that an excess of
3-5 per cent. above the theoretical quantity of lime is necessary to
complete the hydrolysis of a fat when carried on in an open vessel at
100°-105° C., but that if the saponification be conducted under pressure
in autoclaves the amount of lime necessary to secure almost perfect
hydrolysis is reduced to 2-3 per cent. on the fat, the treatment of fats
with 3 per cent. of lime under a pressure of 10 atmospheres producing a
yield of 95 per cent. of fatty acids in seven hours. The lower the
pressure in the autoclave, the lighter will be the colour of the
resultant fatty acids.

_Magnesia._--It has been proposed to substitute magnesia for lime in the
process of saponification under pressure, but comparative experiments
with lime and magnesia, using 3 per cent. of lime and 2.7 per cent. of
magnesia (_Journ. Soc. Chem. Ind._, xii., 163), show that saponification
by means of magnesia is less complete than with lime, and, moreover, the
reaction requires a higher temperature and therefore tends to darken the
product.

_Zinc Oxide._--The use of zinc oxide as accelerating agent has been
suggested by two or three observers. Poullain and Michaud, in 1882, were
granted a patent for this process, the quantity of zinc oxide
recommended to be added to the oil or fat being 0.2 to 0.5 per cent.
Rost, in 1903, obtained a French patent for the saponification of oils
and fats by steam under pressure in the presence of finely divided
metals or metallic oxides, and specially mentions zinc oxide for the
purpose.

It has also been proposed to use zinc oxide in conjunction with lime in
the autoclave to obviate to some extent the discoloration of the fatty
acids.

Other catalytic agents have been recommended from time to time,
including strontianite, lead oxide, caustic baryta, aluminium hydrate,
but none of these is of any practical importance.

_Soda and Potash._--Unlike the preceding bases, the soaps formed by soda
and potash are soluble in water, and constitute the soap of commerce.
These reagents are always used in sufficient quantity to combine with
the whole of the fatty acids contained in an oil or fat, though
doubtless, by the use of considerably smaller quantities, under
pressure, complete resolution of the fatty matter into fatty acids and
glycerol could be accomplished. They are, by far, the most important
saponifying agents from the point of view of the present work, and their
practical use is fully described in Chapter V.



CHAPTER III.

RAW MATERIALS USED IN SOAP-MAKING.

     _Fats and Oils--Waste Fats--Fatty Acids--Less-known Oils and
     Fats of Limited Use--Various New Fats and Oils Suggested for
     Soap-making--Rosin--Alkali (Caustic and
     Carbonated)--Water--Salt--Soap-stock._


_Fats and Oils._--All animal and vegetable oils and fats intended for
soap-making should be as free as possible from unsaponifiable matter, of
a good colour and appearance, and in a sweet, fresh condition. The
unsaponifiable matter naturally present as cholesterol, or phytosterol,
ranges in the various oils and fats from 0.2 to 2.0 per cent. All oils
and fats contain more or less free acidity; but excess of acidity,
though it may be due to the decomposition of the glyceride, and does not
always denote rancidity, is undesirable in soap-making material.
Rancidity of fats and oils is entirely due to oxidation, in addition to
free acid, aldehydes and ketones being formed, and it has been proposed
to estimate rancidity by determining the amount of these latter
produced. It is scarcely necessary to observe how very important it is
that the sampling of fats and oils should be efficiently performed, so
that the sample submitted to the chemist may be a fairly representative
average of the parcel.

In the following short description of the materials used, we give, under
each heading, figures for typical samples of the qualities most suitable
for soap-making.

_Tallows._--Most of the imported tallow comes from America, Australia
and New Zealand. South American mutton tallow is usually of good
quality; South American beef tallow is possessed of a deep yellow colour
and rather strong odour, but makes a bright soap of a good body and
texture. North American tallows are, as a general rule, much paler in
colour than those of South America, but do not compare with them in
consistence. Most of the Australasian tallows are of very uniform
quality and much in demand.

Great Britain produces large quantities of tallow which comes into the
market as town and country tallow, or home melt. Owing to the increasing
demand for edible fat, much of the rough fat is carefully selected,
rendered separately, and the product sold for margarine-making.
Consequently the melted tallow for soap-making is of secondary
importance to the tallow melter.

The following are typical samples of tallow:--

 _______________________________________________________________________
|                                 |                |           |        |
|                                 |                |  Acidity  |        |
|                                 | Saponification | (as Oleic | Titre, |
|                                 |   Equivalent.  |   Acid)   |   °C.  |
|                                 |                | Per Cent. |        |
|_________________________________|________________|___________|________|
|                                 |                |           |        |
| Australian mutton               |     285        |   0.85    |  45    |
| Australian mutton               |     284.4      |   0.48    |  48.3  |
| Australian beef                 |     284.2      |   1.68    |  43.9  |
| Australian beef                 |     283.6      |   0.85    |  42.6  |
| Australian mixed                |     285.1      |   3.52    |  44    |
| Australian mixed                |     284.6      |   1.89    |  43.5  |
| South American mutton           |     284.5      |   1.11    |  47    |
| South American mutton           |     285        |   0.90    |  47.4  |
| South American beef             |     284.7      |   0.81    |  45    |
| South American beef             |     284        |   0.94    |  44    |
| North American mutton           |     284.3      |   1.32    |  44    |
| North American mutton           |      85        |   2.18    |  43.2  |
| North American beef, fine       |     284.5      |   1.97    |  41.5  |
| North American beef, good       |     283.8      |   4.30    |  42    |
| North American ordinary         |     285.2      |   5.07    |  41.75 |
| North American prime city       |     286        |   1.01    |  41.2  |
| Selected English mutton         |     283.9      |   1.45    |  47    |
| Selected English beef           |     284.2      |   2.40    |  44    |
| Home-rendered or country tallow |     284.6      |   5.1     |  43    |
| Town tallow                     |     285.3      |   7.4     |  42.5  |
|_________________________________|________________|___________|________|

Tallow should absorb from 39 to 44 per cent. iodine.

_Lard._--Lard is largely imported into this country from the United
States of America. The following is a typical sample of American hog's
fat offered for soap-making:--

 ________________________________________________________
|                |                 |        |            |
| Saponification |     Acidity     | Titre, | Refractive |
|  Equivalent.   | (as Oleic Acid) |   °C.  |   Index    |
|                |    Per Cent.    |        |  at 60° C. |
|________________|_________________|________|____________|
|                |                 |        |            |
|      286       |       0.5       |  37.5  |   1.4542   |
|________________|_________________|________|____________|

Lard should absorb 59 to 63 per cent. iodine.

_Cocoa-nut Oil._--The best known qualities are Cochin and Ceylon oils,
which are prepared in Cochin (Malabar) or the Philippine Islands and
Ceylon respectively.

The dried kernels of the cocoa-nut are exported to various ports in
Europe, and the oil obtained comes on the market as Continental Coprah
Oil, with the prefix of the particular country or port where it has been
crushed, _e.g._, Belgian, French and Marseilles Coprah Oil. Coprah is
also imported into England, and the oil expressed from it is termed
English Pressed Coprah.

The following are typical examples from bulk:--

 _________________________________________________________________________
|                |                |                 |        |            |
|                | Saponification |     Acidity     | Titre, | Refractive |
|                |   Equivalent.  | (as Oleic Acid) |   °C.  |    Index   |
|                |                |    Per Cent.    |        | at 25° C.  |
|________________|________________|_________________|________|____________|
|                |                |                 |        |            |
| Cochin oil     |      215.5     |       1.5       |  23.5  |   1.4540   |
| Cochin oil     |      214.3     |       2.6       |  22.1  |   1.4541   |
| Ceylon oil     |      214.6     |       5.47      |  23    |   1.4535   |
| Ceylon oil     |      216       |       3.95      |  22.75 |   1.4535   |
| Belgian coprah |      214.2     |       1.65      |  23    |   1.4541   |
| Belgian coprah |      215       |       2.60      |  22.1  |   1.4540   |
| French coprah  |      214.2     |       6.55      |  23    |   1.4535   |
| French coprah  |      214.8     |       7.42      |  22    |   1.4540   |
| Pressed coprah |      215.8     |       7.45      |  22.2  |   1.4542   |
| Pressed coprah |      216       |       9.41      |  22    |   1.4555   |
|________________|________________|_________________|________|____________|

Cocoa-nut oil should absorb 8.9 to 9.3 per cent. iodine.

_Palm-nut Oil._--The kernels of the palm-tree fruit are exported from
the west coast of Africa to Europe, and this oil obtained from them.
Typical samples of English and Hamburg oils tested:--

 _________________________________________________________
|                |                 |        |            |
| Saponification |     Acidity     | Titre, | Refractive |
|   Equivalent.  | (as Oleic Acid) |   °C.  |    Index   |
|                |    Per Cent.    |        | at 25° C.  |
|________________|_________________|________|____________|
|                |                 |        |            |
|       225      |       4.4       |  24    |   1.4553   |
|       227      |       7.7       |  23.8  |   1.4553   |
|________________|_________________|________|____________|

Palm-nut oil should absorb 10 to 13 per cent. iodine.

_Olive Oil._--The olive is extensively grown in Southern Europe and in
portions of Asia and Africa bordering the Mediterranean Sea. The fruit
of this tree yields the oil.

The free fatty acid content of olive oil varies very considerably. Very
fine oils contain less than 1 per cent. acidity; commercial oils may be
graded according to their free acidity, _e.g._, under 5 per cent., under
10 per cent., etc., and it entirely depends upon the desired price of
the resultant soap as to what grade would be used. The following is a
typical sample for use in the production of high-class toilet soap:--

_________________________________________________________
|                |                 |        |            |
| Saponification |     Acidity     | Titre, | Refractive |
|   Equivalent.  | (as Oleic Acid) |   °C.  |    Index   |
|                |    Per Cent.    |        | at 15° C.  |
|________________|_________________|________|____________|
|                |                 |        |            |
|      288       |       1.8       |  21    |   1.4704   |
|________________|_________________|________|____________|

Olive oil should absorb 80 to 83 per cent. iodine.

_Olive-kernel oil_, more correctly termed _Sulphur olive oil_.

The amount of free fatty acids is always high and ranges from 40-70 per
cent., and, of course, its glycerol content is proportionately variable.
The free acidity increases very rapidly, and is, doubtless, due to the
decomposition of the neutral oil by the action of hydrolytic ferment.

A representative sample of a parcel tested:--

 _______________________________________________
|                |                 |            |
| Saponification |     Acidity     | Refractive |
|   Equivalent.  | (as Oleic Acid) |    Index   |
|                |    Per Cent.    | at 20° C.  |
|________________|_________________|____________|
|                |                 |            |
|       298      |      40.96      |   1.4666   |
|________________|_________________|____________|

_Palm oil_ is produced from the fruit of palm trees, which abound along
the west coast of Africa. Lagos is the best quality, whilst Camaroons,
Bonny, Old Calabar and New Calabar oils are in good request for
bleaching purposes.

Analysis of typical samples of crude palm oil has given:--

 _________________________________________________________
|                |                 |        |             |
| Saponification |     Acidity     | Titre, |  Water and  |
|   Equivalent.  | (as Oleic Acid) |   °C.  | Impurities, |
|                |    Per Cent.    |        |  Per Cent.  |
|________________|_________________|________|_____________|
|                |                 |        |             |
|       278      |      10.7       |  45    |     1.6     |
|       280      |      31.2       |  44.5  |     2.8     |
|________________|_________________|________|_____________|

Palm oil should absorb 51 to 56 per cent. iodine.

In the lower qualities we have examples of the result of hydrolytic
decomposition by enzymes, the free acidity often amounting to 70 per
cent.

_Cotton-seed Oil._--This oil is expressed from the seeds separated from
the "wool" of the various kinds of cotton tree largely cultivated in
America and Egypt.

In its crude state cotton-seed oil is a dark fluid containing
mucilaginous and colouring matter, and is not applicable for
soap-making. The following figures are representative of well-refined
cotton-seed oils:--

 _________________________________________________________________________
|           |                |                 |        |            |
| Specific  | Saponification |     Acidity     | Titre, | Refractive |
| Gravity   |   Equivalent.  | (as Oleic Acid) |   °C.  |    Index   |
| at 15° C. |                |    Per Cent.    |        | at 20° C.  |
|___________|________________|_________________|________|____________|
|           |                |                 |        |            |
|  0.9229   |       290      |       0.24      |  33.6  |   1.4721   |
|  0.924    |       299      |       0.39      |  35    |   1.4719   |
|___________|________________|_________________|________|____________|

Cotton-seed oil should absorb 104 to 110 per cent. iodine.

_Cotton-seed Stearine._--The product obtained by pressing the deposit
which separates on chilling refined cotton-seed oil.

A typical sample tested:--

 ___________________________________________
|                |                 |        |
| Saponification |     Acidity     | Titre, |
|   Equivalent.  | (as Oleic Acid) |   °C.  |
|                |    Per Cent.    |        |
|________________|_________________|________|
|                |                 |        |
|     285.1      |      0.05       |  38    |
|________________|_________________|________|

_Arachis Oil._--The earth-nut or ground-nut, from which arachis oil is
obtained, is extensively cultivated in North America, India and Western
Africa. Large quantities are exported to Marseilles where the oil is
expressed. Arachis oil enters largely into the composition of Marseilles
White Soaps.

Representative samples of commercial and refined oils tested:--

 ______________________________________________________________________
|            |           |           |           |        |            |
|            | Specific  |  Saponi-  |  Acidity  |        | Refractive |
|            | Gravity   | fication  | (as Oleic | Titre, |    Index   |
|            | at 15° C. |  Equi-    |   Acid)   |   °C.  | at 20° C.  |
|            |           |  valent   | Per Cent. |        |            |
|____________|___________|___________|___________|________|____________|
|            |           |           |           |        |            |
| Commercial |   0.9184  |    298    |    2.6    |  28.6  |            |
| Refined    |   0.9205  |    285    |    0.22   |  24.0  |   1.4712   |
|____________|___________|___________|___________|________|____________|

Arachis oil should absorb 90 to 98 per cent. iodine.

_Maize Oil._--America (U.S.) produces very large quantities of maize
oil.

Typical samples of crude and refined oil gave these figures:--

 ______________________________________________________________________
|            |           |           |           |        |            |
|            | Specific  |  Saponi-  |  Acidity  |        | Refractive |
|            | Gravity   | fication  | (as Oleic | Titre, |    Index   |
|            | at 15° C. |  Equi-    |   Acid)   |   °C.  | at 20° C.  |
|            |           |  valent   | Per Cent. |        |            |
|____________|___________|___________|___________|________|____________|
|            |           |           |           |        |            |
| Crude      |   0.9246  |    294    |    1.41   |  15    |            |
| Refined    |   0.9248  |    294.1  |    0.40   |  17.2  |   1.4766   |
|____________|___________|___________|___________|________|____________|

Maize oil should absorb 120 to 128 per cent. iodine.

_Sesame Oil._--Sesame oil is very largely pressed in Southern France
from the seeds of the sesame plant which is cultivated in the Levant,
India, Japan and Western Africa.

A fairly representative sample of French expressed oil tested:--

 ____________________________________________________________________
|           |                |                 |        |            |
| Specific  | Saponification |     Acidity     | Titre, | Refractive |
| Gravity   |   Equivalent.  | (as Oleic Acid) |   °C.  |    Index   |
| at 15° C. |                |    Per Cent.    |        | at 20° C.  |
|___________|________________|_________________|________|____________|
|           |                |                 |        |            |
|   0.9227  |      295.2     |       1.84      |  22.8  |   1.4731   |
|___________|________________|_________________|________|____________|

Sesame oil should absorb 108 to 110 per cent. iodine.

_Linseed Oil._--Russia, India, and Argentine Republic are the principal
countries which extensively grow the flax plant, from the seeds of which
linseed oil is pressed. It is used to a limited extent in soft-soap
making.

A good sample gave on analysis:--

 ____________________________________________________________________
|           |                |                 |        |            |
| Specific  | Saponification |     Acidity     | Titre, | Refractive |
| Gravity   |   Equivalent.  | (as Oleic Acid) |   °C.  |    Index   |
| at 15° C. |                |    Per Cent.    |        | at 15° C.  |
|___________|________________|_________________|________|____________|
|           |                |                 |        |            |
|   0.935   |      292       |       1.2       |  20    |   1.4840   |
|___________|________________|_________________|________|____________|

Linseed oil should absorb 170 to 180 per cent. iodine.

_Hemp-seed oil_ is produced from the seeds of the hemp plant which grows
in Russia. This oil is used in soft soap-making, more particularly on
the Continent.

A typical sample gave the following figures:--

 __________________________________________________
|           |                |        |            |
| Specific  | Saponification | Titre, |            |
| Gravity   |   Equivalent.  |   °C.  | Iodine No. |
| at 15° C. |                |        |            |
|___________|________________|________|____________|
|           |                |        |            |
|   0.926   |     292.6      |  15.8  |    143     |
|___________|________________|________|____________|

_Sunflower oil_ is produced largely in Russia.

A specimen tested:--

 ____________________________________________________________________
|           |                |                 |        |            |
| Specific  | Saponification |     Acidity     | Titre, |            |
| Gravity   |   Equivalent.  | (as Oleic Acid) |   °C.  | Iodine No. |
| at 15° C. |                |    Per Cent.    |        |            |
|___________|________________|_________________|________|____________|
|           |                |                 |        |            |
|   0.9259  |     290.7      |       0.81      |   17   |   126.2    |
|___________|________________|_________________|________|____________|

_Castor Oil._--The castor oil plant is really a native of India, but it
is also cultivated in the United States (Illinois) and Egypt.

A typical commercial sample tested:--

 ________________________________________________________________________
|           |           |        |            |             |            |
|  Saponi-  |  Acidity  |        |            |   Optical   | Refractive |
| fication  | (as Oleic | Titre, | Iodine No. |  Rotation   |    Index   |
|  Equi-    |   Acid)   |   °C.  |            | [alpha]_{D} | at 25° C.  |
|  valent   | Per Cent. |        |            |             |            |
|___________|___________|________|____________|_____________|____________|
|           |           |        |            |             |            |
|    310    |    1.5    |  2.8   |    84.1    |   + 4° 50'  |   1.4787   |
|___________|___________|________|____________|_____________|____________|

_Fish and Marine Animal Oils._--Various oils of this class have, until
recently, entered largely into the composition of soft soaps, but a
demand has now arisen for soft soaps made from vegetable oils.

We quote a few typical analyses of these oils:--

 _________________________________________________________________________
|                  |          |          |           |        |           |
|                  | Specific |  Saponi- |  Acidity  |        | Unsaponi- |
|                  | Gravity  | fication | (as Oleic | Titre, |  fiable   |
|                  | at 15°C. |  Equi-   |   Acid)   |   °C.  |   Matter  |
|                  |          |  valent  | Per Cent. |        | Per Cent. |
|__________________|__________|__________|___________|________|___________|
|                  |          |          |           |        |           |
| Pale seal oil    |   0.9252 |    289   |   0.947   |  15.5  |   0.8     |
| Straw seal oil   |   0.9231 |    288   |   4.77    |  15.8  |   1.2     |
| Brown seal oil   |   0.9253 |    291   |  16.38    |  16.2  |   1.9     |
| Whale oil        |   0.9163 |    297   |   1.49    |  16.1  |   1.8     |
| Dark whale oil   |   0.9284 |    303   |  12.60    |  21.8  |   2.4     |
| Japan fish oil   |   0.9336 |    296   |   4.79    |  26    |   0.67    |
| Japan fish oil   |   0.9325 |    302   |  10.43    |  28    |   1.55    |
| Brown cod oil    |   0.9260 |    313   |  14.91    |  21.8  |   1.9     |
| Pure herring oil |   0.9353 |    288   |  11.39    |  21.6  |   1.5     |
| Kipper oil       |   0.9271 |    297   |   5.14    |  22.7  |   3.25    |
|__________________|__________|__________|___________|________|___________|

_Waste Fats._--Under this classification may be included marrow fat,
skin greases, bone fats, animal grease, melted stuff from hotel and
restaurant refuse, and similar fatty products. The following is a fair
typical selection:--

 _______________________________________________________________
|                   |                |                 |        |
|                   | Saponification |     Acidity     | Titre, |
|                   |   Equivalent.  | (as Oleic Acid) |   °C.  |
|                   |                |    Per Cent.    |        |
|___________________|________________|_________________|________|
|                   |                |                 |        |
| Marrow fat        |      283.3     |       3.6       |  38.7  |
| White skin grease |      287.2     |       4.3       |  36.4  |
| Pale skin grease  |      286.3     |       9.87      |  35.7  |
| Pale bone fat     |      289.7     |       8.8       |  40.7  |
| Brown bone fat    |      289.1     |      11.0       |  41    |
| Brown bone fat    |      292       |      20.5       |  40.2  |
| Animal grease     |      289.4     |      38.1       |  40.4  |
| Melted stuff      |      286.3     |      12.8       |  37.7  |
|___________________|________________|_________________|________|

The materials in the above class require to be carefully examined for
the presence of unsaponifiable matter, lime salts and other impurities.

_Fatty Acids._--We have already described the various methods of
liberating fatty acids by hydrolysis or saponification.

Under this heading should also be included stearines produced by
submitting distilled fat to hydraulic pressure, the distillates from e
from unsaponifiable matter, cocoa-nut oleine, a bye-product from the
manufacture of edible cocoa-nut butter and consisting largely of free
acids, and palm-nut oleine obtained in a similar manner from palm-nut
oil.

These are all available for soap-making.


LESS-KNOWN OILS AND FATS OF LIMITED USE.

_Shea Butter._--Shea butter is extracted from the kernels of the _Bassia
Parkii_ and exported from Africa and Eastern India. This fat is somewhat
tough and sticky, and the amount of unsaponifiable matter present is
sometimes considerable. Samples examined by us gave the following
data:--

 _______________________________________________________________
|                |                 |        |                   |
| Saponification |     Acidity     | Titre, |    Refractive     |
|   Equivalent.  | (as Oleic Acid) |   °C.  |       Index       |
|                |    Per Cent.    |        |    at 60° C.      |
|________________|_________________|________|___________________|
|                |                 |        |                   |
|       313      |       8.2       |  53.2  | 1.4566            |
|       303      |       7.33      |  53    | 1.4558            |
|                |                 |        | 1.4471 (F. Acids) |
|________________|_________________|________|___________________|

_Mowrah-seed Oil._--The mowrah-seed oil now offered for soap-making is
derived from the seeds of _Bassia longifolia_ and _Bassia latifolia_. It
is largely exported from India to Belgium, France and England. The
following are the results of some analyses made by us:--

 _________________________________________________________
|                |                 |        |            |
| Saponification |     Acidity     | Titre, | Refractive |
|   Equivalent.  | (as Oleic Acid) |   °C.  |    Index   |
|                |    Per Cent.    |        | at 60° C.  |
|________________|_________________|________|____________|
|                |                 |        |            |
|       291      |      10         |  43.4  |   1.4518   |
|       291.5    |       7.1       |  42.7  |            |
|       291.2    |       9.9       |  43.8  |            |
|       292      |      11.26      |  40.5  |            |
|________________|_________________|________|____________|

_Chinese vegetable tallow_ is the name given to the fat which is found
coating the seeds of the "tallow tree" (_Stillingia sebifera_) which is
indigenous to China and has been introduced to India where it
flourishes. The following is a typical sample:--

 _____________________________________
|                |           |        |
| Saponification |  Acidity  | Titre, |
|   Equivalent   | Per Cent. |  °C.   |
|________________|___________|________|
|                |           |        |
|     280.2      |   5.24    |  52.5  |
|________________|___________|________|

The seeds of the "tallow tree" yield an oil (stillingia oil) having
drying properties.

_Borneo Tallow._--The kernels of several species of _Hopea_ (or
_Dipterocarpus_), which flourish in the Malayan Archipelago, yield a fat
known locally as Tangawang fat. This fat is moulded (by means of bamboo
canes) into the form of rolls about 3 inches thick, and exported to
Europe as Borneo Tallow.

A sample tested by one of us gave the following data:--

 ___________________________________________
|                |                 |        |
| Saponification |     Acidity     | Titre, |
|   Equivalent.  | (as Oleic Acid) |   °C.  |
|                |    Per Cent.    |        |
|________________|_________________|________|
|                |                 |        |
|      292       |       36        |  50.8  |
|________________|_________________|________|

_Kapok oil_ is produced from a tree which is extensively grown in the
East and West Indies. The Dutch have placed it on the market and the
figures given by Henriques (_Chem. Zeit._, 17, 1283) and Philippe
(_Monit. Scient._, 1902, 730), although varying somewhat, show the oil
to be similar to cotton-seed oil.


VARIOUS NEW FATS AND OILS SUGGESTED FOR SOAP-MAKING.

_Carapa_ or _Andiroba oil_, derived from the seeds of a tree (_Carapa
Guianensis_) grown in West Indies and tropical America, has been
suggested as suitable for soap-making. Deering (_Imperial Institute
Journ._, 1898, 313) gives the following figures:--

 ____________________________________________
|                |           |               |
| Saponification |  Acidity  | Melting Point |
|   Equivalent   | Per Cent. |   of Fatty    |
|                |           |   Acids, °C.  |
|________________|___________|_______________|
|                |           |               |
|      287       |    12     |      89       |
|________________|___________|_______________|

Another observer (_Rev. Chem. Ind._, 13, 116) gives the setting point of
the fatty acids as 56.4° C.

_Candle-nut oil_ obtained from the seeds of a tree flourishing in India
and also the South Sea Islands.

The following figures have been published:--

 _____________________________________________________________________________
|           |       |            |            |
| Saponi-   |       |            |            |
| fication  | Titre,| Iodine No. |  Observers.| References.
| Equiv-    |       |            |            |
| alent.[1] |   °C. |            |            |
|___________|_______|____________|____________|_______________________________
|           |       |            |            |
| 299-304.9 |  13   | 136.3-139.3| De Negri   |_Chem. Centr._, 1898, p. 493.
|    291    |       |    163.7   | Lewkowitsch|_Chem. Revue_, 1901, p. 156.
|    296    |  12.5 |    152.8   | Kassler    |_Farben-Zeitung_, 1903, p. 359.
|___________|_______|____________|____________|_______________________________

_Curcas oil_ is produced in Portugal from the seeds of the "purging nut
tree," which is similar to the castor oil plant, and is cultivated in
Cape Verde Islands and other Portuguese Colonies.

The following data have been observed:--

______________________________________________________________________________
|           |       |            |            |
| Saponi-   |       |            |            |
| fication  | Titre,| Iodine No. |  Observers.| References.
| Equiv-    |       |            |            |
| alent.[2] |   °C. |            |            |
|___________|_______|____________|____________|_______________________________
|           |       |            |            |
|  291.4    | 0.36  |    99.5    | Archbut    |_J. S. C. Ind._, 1898, p. 1010.
|  290.3    | 4.46  |    98.3    | Lewkowitsch|_Chem. Revue_, 1898, p. 211.
|  283.1    | 0.68  |   107.9    | Klein      |_Zeits. angew. Chem._,
|           |       |            |            |   1898, p. 1012.
|___________|_______|____________|____________|_______________________________

The titre is quoted by Lewkowitsch as 28.6° C.

_Goa butter_ or _Kokum butter_ is a solid fat obtained from the seeds of
_Garcinia indica_, which flourishes in India and the East Indies.
Crossley and Le Sueur (_Journ. Soc. Chem. Industry_, 1898, p. 993)
during an investigation of Indian oils obtained these results:--

 _________________________________________
|                |           |            |
| Saponification |  Acidity  | Iodine No. |
| Equivalent.[3] | Per Cent. |            |
|________________|___________|____________|
|                |           |            |
|      300       |    7.1    |   34.2     |
|________________|___________|____________|

_Safflower oil_ is extracted from the seeds of the _Carthamus
tinctorius_, which, although indigenous to India and the East Indies, is
extensively cultivated in Southern Russia (Saratowa) and German East
Africa. Its use has been suggested for soft-soap making. The following
figures have been published:--

 ____________________________________________________________________________
|         |         |        |             |
|         | Saponi  |        |             |
|         |fication | Iodine |  Observers. | References.
|         | Equiv-  | No.    |             |
|         |alent.[4]|        |             |
|_________|_________|________|_____________|_________________________________
|         |         |        |             |
| Average |  295.5  | 141.29 | Crossley and| _J. S. C. Ind._, 1898, p. 992;
|   of    |         |        |   Le Sueur  |   _J. S. C. Ind._, 1900, p. 104.
| Twelve  |  287.1  | 141.6  | Shukoff     |_Chem. Revue_, 1901, p. 250.
| Samples |  289.2  | 130    | Tylaikow    |_Chem. Revue_, 1902, p. 106.
|         |  293.7  | 142.2  | Fendler     |_Chem. Zeitung_, 1904, p. 867.
|_________|_________|________|_____________|_________________________________

_Maripa fat_ is obtained from the kernels of a palm tree flourishing in
the West Indies, but, doubtless, the commercial fat is obtained from
other trees of the same family. It resembles cocoa-nut oil and gives the
following figures:--

 ___________________________________________________________________________
|          |        |           |           |
| Saponi-  |        | Melting   |           |
| fication |        | Point     |           |
| Equiv-   | Iodine | of Fatty  |           |
| alent.[5]| No.    | Acids, °C.| Observer. | Reference.
|__________|________|___________|___________|_______________________________
|          |        |           |           |
|  217     | 9.49   |   25      | Bassière  |_J. S. C. Ind._, 1903, p. 1137.
|__________|________|___________|___________|_______________________________

_Niam fat_, obtained from the seeds of _Lophira alata_, which are found
extensively in the Soudan. The fat, as prepared by natives, has been
examined by Lewkowitsch, and more recently Edie has published the
results of an analysis. The figures are as follows:--

__________________________________________________________________________
|           |       |        |            |
| Saponi-   |       |        |            |
| fication  | Titre,| Iodine |  Observers.| References.
| Equiv-    |       | No.    |            |
| alent.[6] |   °C. |        |            |
|___________|_______|________|____________|_______________________________
|           |       |        |            |
|  295.1    | 78.12 |  42.5  | Lewkowitsch|_J. S. C. Ind._, 1907, p. 1266.
|  287.7    | 75.3  |        | Edïe.      |_Quart. J. Inst. Comm.
|           |       |        |            |   Research in Tropics._
|___________|_______|________|____________|_______________________________


_Cohune-nut oil_ is produced from the nuts of the cohune palm, which
flourishes in British Honduras. This oil closely resembles cocoa-nut and
palm-nut oils and is stated to saponify readily and yield a soap free
from odour. The following figures, obtained in the Laboratory of the
Imperial Institute, are recorded in the official _Bulletin_, 1903, p.
25:--

 ________________________________________________
|                |            |                  |
| Saponification | Iodine No. | Melting Point of |
|  Equivalent.   |            | Fatty Acids, °C. |
|________________|____________|__________________|
|                |            |                  |
|  253.9-255.3   |  12.9-13.6 |      27-30       |
|________________|____________|__________________|

_Mafoureira_ or _Mafura tallow_ from the nuts of the mafoureira tree,
which grows wild in Portuguese East Africa. The following figures are
published:--

______________________________________________________________________________
|             |                |           |
| Saponi-     |                |           |
|  fication   |                | Iodine    | References.
| Equi-       |                |     No.   |
| valent.     |                |           |
|_____________|________________|___________|___________________________________
|             | Titre, °C.     |           |
|   253.8     |   44-48        |  46.14    | De Negri and Fabris, _Annal. del
|             |                |           |  Lab. Chim. Delle Gabelle_,
|             |                |           |  1891-2, p. 271.
|             | Acidity        |           |
|             | (as Oleic Acid)|           |
|             | Per Cent.      |           | _Bulletin Imp. Inst._,
| 232.8-233.7 |  21.26         | 47.8-55.8 |   1903, p. 27.
|_____________|________________|___________|___________________________________

_Pongam oil_, obtained from the beans of the pongam tree, which
flourishes in East India, has been suggested as available for the soap
industry, but the unsaponifiable matter present would militate against
its use. Lewkowitsch (_Analyst_, 1903, pp. 342-44) quotes these
results:--


 _____________________________________________________________________
|                 |            |        |           |                 |
|                 |  Saponi-   |        |           |                 |
|                 | fication   | Iodine | Acidity,  | Unsaponifiable, |
|                 |  Equi-     |   No.  | Per Cent. |    Per Cent.    |
|                 | valent.[7] |        |           |                 |
|_________________|____________|________|___________|_________________|
|                 |            |        |           |                 |
| Oil extracted   |    315     |  94    |   3.05    |       9.22      |
|  in laboratory  |            |        |           |                 |
| Indian specimen |    306     |  89.4  |   0.5     |       6.96      |
|_________________|____________|________|___________|_________________|

_Margosa oil_ is obtained from the seeds of _Melia azedarach_, a tree
which is found in most parts of India and Burma.

Lewkowitsch (_Analyst_, 1903, pp. 342-344) gives these figures:--

 __________________________________
|                |        |        |
| Saponification | Iodine | Titre, |
| Equivalent.[8] |   No.  |   °C.  |
|________________|________|________|
|                |        |        |
|     284.9      |  69.6  |   42   |
|________________|________|________|

_Dika fat_ or _Wild Mango oil_ is obtained from the seed kernels of
various kinds of _Irvingia_ by boiling with water. Lemarié (_Bulletin
Imp. Inst._, 1903, p. 206) states that this fat is used in the place of
cocoa-nut oil in the manufacture of soap. Lewkowitsch (_Analyst_, 1905,
p. 395) examined a large sample of dika fat obtained from seeds of
_Irvingia bateri_ (South Nigeria) and gives the following data:--

 ____________________________________________________
|                |        |        |                 |
| Saponification | Iodine | Titre, | Unsaponifiable, |
| Equivalent.[9] |   No.  |  °C.   |   Per Cent.     |
|________________|________|________|_________________|
|                |        |        |                 |
|     229.4      |   5.2  |  34.8  |      0.73       |
|________________|________|________|_________________|

_Baobab-seed Oil._--Balland (_Journ. Pharm. Chem._, 1904, p. 529,
abstracted in _Journ. Soc. Chem. Ind._, 1905, p. 34) states that the
natives of Madagascar extract, by means of boiling water, from the seeds
of the baobab tree, a whitish solid oil, free from rancidity, and
possessed of an odour similar to Tunisian olive oil. He suggests that it
may, with advantage, replace cocoa-nut oil in soap manufacture.

_Persimmon-seed Oil._--Lane (_J. S. C. Ind._, 1905, p. 390) gives
constants for this oil which he describes as semi-drying, of brownish
yellow colour, and having taste and odour like pea-nut (arachis) oil.
The following are taken from Lane's figures:--

 ___________________________________
|                 |        |        |
| Saponification  | Iodine | Titre, |
| Equivalent.[10] |   No.  |  °C.   |
|_________________|________|________|
|                 |        |        |
|     298.4       | 115.6  |  20.2  |
|_________________|________|________|

_Wheat oil_, extracted from the wheat germ by means of solvents, has
been suggested as applicable for soap-making (H. Snyder, abstr. _J. S.
C. Ind._, 1905, p. 1074). The following figures have been published:--

_______________________________________________________________________________
|           |         |        |        |             |
| Saponi-   |         |        |        |             |
|  fication | Acidity,| Iodine | Titre, | Observers.  | References.
| Equiv-    | Per     |  No.   |        |             |
| alent.[11]| Cent.   |        |   °C.  |             |
|___________|_________|________|________|_____________|________________________
|           |         |        |        |             |
|  306      |   5.65  | 115.17 |  29.7  | De Negri.   | _Chem. Zeit._, 1898
|           |         |        |        |             |  (abstr. _J. S. C. I._,
|           |         |        |        |             |  1898, p. 1155).
|  297      |  20     | 115.64 |        | Frankforter | _J. Amer. C. Soc._,
|           |         |        |        | & Harding   |  1899, 758-769 (abstr.
|           |         |        |        |             |  in _J. S. C. I._,
|           |         |        |        |             |  1899, p. 1030).
|___________|_________|________|________|_____________|________________________

_Tangkallah fat_, from the seeds of a tree growing in Java and the
neighbouring islands, is suitable for soap-making. Schroeder (_Arch.
Pharm._, 1905, 635-640, abstracted in _J. S. C. Ind._, 1906, p. 128)
gives these values:--

 _______________________________________________________
|                |           |        |                 |
| Saponification | Acidity,  | Iodine | Unsaponifiable, |
| Equivalent.[12]| Per Cent. |   No.  |    Per Cent.    |
|________________|___________|________|_________________|
|                |           |        |                 |
|      209       |    1.67   |  2.28  |      1.44       |
|________________|___________|________|_________________|

It is a hard fat, nearly white, possessing neither taste nor
characteristic odour and solidifying at about 27° C.

_Oil of Inoy-kernel._--(_Bulletin Imp. Inst._, 1906, p. 201). The seeds
of Poga oleosa from West Africa yield on extraction an oil which gives
the figures quoted below, and is suggested as a soap-maker's material:--

 __________________________________
|                |        |        |
| Saponification | Iodine | Titre, |
| Equivalent.    |   No.  |   °C.  |
|________________|________|________|
|                |        |        |
|      304       | 89.75  |   22   |
|________________|________|________|


ROSIN.

Rosin is the residuum remaining after distillation of spirits of
turpentine from the crude oleo-resin exuded by several species of the
pine, which abound in America, particularly in North Carolina, and also
flourish in France and Spain. The gigantic forests of the United States
consist principally of the long-leaved pine, _Pinus palustris
(Australis)_, whilst the French and Spanish oleo-resin is chiefly
obtained from _Pinus pinaster_, which is largely cultivated.

Rosin is a brittle, tasteless, transparent substance having a smooth
shining fracture and melting at about 135° C. (275° F.). The American
variety possesses a characteristic aromatic odour, which is lacking in
those from France and Spain. It is graded by samples taken out of the
top of every barrel, and cut into 7/8 of an inch cubes, which must be
uniform in size--the shade of colour of the cube determines its grade
and value.

The grades are as follows:--

          W. W.  (Water white.)
          W. G.  (Window glass.)
          N.     (Extra pale.)
          M.     (Pale.)
          K.     (Low pale.)
          I.     (Good No. 1.)
          H.     (No. 1.)
          G.     (Low No. 1.)
          F.     (Good No. 2.)
          E.     (No. 2.)
          D.     (Good strain.)
          C.     (Strain.)
          B.     (Common strain.)
          A.     (Common.)

Unsaponifiable matter is present in rosin in varying amounts.

Below are a few typical figures taken from a large number of collated
determinations:--

 ________________________________________________________________
|                |                |          |          |        |
|                | Saponification |  Total   |   Free   | Iodine |
|                |  Equivalent.   | Acid No. | Acid No. |   No.  |
|________________|________________|__________|__________|________|
|                |                |          |          |        |
| American W. W. |     330.5      |  169.7   |  119.1   | 126.9  |
| American N.    |     312.3      |  179.6   |  161.4   | 137.8  |
| French         |     320.5      |  175     |  168     | 120.7  |
| Spanish        |     313.4      |  179     |  160     | 129.8  |
|________________|________________|__________|__________|________|


ALKALI (CAUSTIC AND CARBONATED).

The manufacture of alkali was at one time carried on in conjunction with
soap-making, but of late years it has become more general for the soap
manufacturer to buy his caustic soda or carbonated alkali from the
alkali-maker.

Although there are some alkali-makers who invoice caustic soda and soda
ash in terms of actual percentage of sodium oxide (Na_{2}O), it is the
trade custom to buy and sell on what is known as the English degree,
which is about 1 per cent. higher than this.

The English degree is a survival of the time when the atomic weight of
sodium was believed to be twenty-four instead of twenty-three, and,
since the error on 76 per cent. Na_{2}O due to this amounts to about 1
per cent., may be obtained by adding this figure to the sodium oxide
really present.

_Caustic soda_ (sodium hydrate) comes into commerce in a liquid form as
90° Tw. (and even as high as 106° Tw.), and other degrees of dilution,
and also in a solid form in various grades as 60°, 70°, 76-77°, 77-78°.
These degrees represent the percentage of sodium oxide (Na_{2}O) present
plus the 1 per cent. The highest grade, containing as it does more
available caustic soda and less impurities, is much more advantageous in
use.

_Carbonate of soda_ or _soda ash_, 58°, also termed "light ash," and
"refined alkali". This is a commercially pure sodium carbonate
containing about 0.5 per cent. salt (NaCl). The 58° represents the
English degrees and corresponds to 99 per cent. sodium carbonate
(Na_{2}CO_{3}).

_Soda ash_, 48°, sometimes called "caustic soda ash," often contains
besides carbonate of soda, 4 per cent. caustic soda (sodium hydrate),
and 10 per cent. salt (sodium chloride), together with water and
impurities.

The 48 degrees refers to the amount of alkali present in terms of sodium
oxide (Na_{2}O), but expressed as English degrees.

_Caustic potash_ (potassium hydrate) is offered as a liquid of 50-52° B.
(98-103° Tw.) strength, and also in solid form as 75-80° and 88-92°. The
degrees in the latter case refer to the percentage of potassium hydrate
(KHO) actually present.

_Carbonate of Potash._--The standard for refined carbonate of potash is
90-92 per cent. of actual potassium carbonate (K_{2}CO_{3}) present,
although it can be obtained testing 95-98 per cent.


OTHER MATERIALS.

_Water._--Water intended for use in soap-making should be as soft as
possible. If the water supply is hard, it should be treated chemically;
the softening agents may be lime and soda ash together, soda ash alone,
or caustic soda. There are many excellent plants in vogue for water
softening, which are based on similar principles and merely vary in
mechanical arrangement. The advantages accruing from the softening of
hard water intended for steam-raising are sufficiently established and
need not be detailed here.

_Salt_ (sodium chloride or common salt, NaCl) is a very important
material to the soap-maker, and is obtainable in a very pure state.

Brine, or a saturated solution of salt, is very convenient in
soap-making, and, if the salt used is pure, will contain 26.4 per cent.
sodium chloride and have a density of 41.6° Tw. (24.8° B.).

The presence of sulphates alters the density, and of course the sodium
chloride content.

Salt produced during the recovery of glycerine from the spent lyes often
contains sulphates, and the density of the brine made from this salt
ranges higher than 42° Tw. (25° B.).

_Soapstock._--This substance is largely imported from America, where it
is produced from the dark-coloured residue, termed mucilage, obtained
from the refining of crude cotton-seed oil. Mucilage consists of
cotton-seed oil soap, together with the colouring and resinous
principles separated during the treatment of the crude oil. The
colouring matter is removed by boiling the mucilage with water and
graining well with salt; this treatment is repeated several times until
the product is free from excess of colour, when it is converted into
soap and a nigre settled out from it.

Soapstock is sold on a fatty acid basis; the colour is variable.

FOOTNOTES:

[1] Calculated by us from saponification value.

[2] Calculated by us from saponification value.

[3] Calculated by us from saponification value.

[4] Calculated by us from saponification value.

[5] Calculated by us from saponification value.

[6] Calculated by us from saponification value.

[7] Calculated by us from saponification value.

[8] Calculated by us from saponification value.

[9] Calculated by us from saponification value.

[10] Calculated by us from saponification value.

[11] Calculated by us from saponification value.

[12] Calculated by us from saponification value.



CHAPTER IV.

BLEACHING AND TREATMENT OF RAW MATERIALS INTENDED FOR SOAP-MAKING.

     _Palm Oil--Cotton-seed Oil--Cotton-seed "Foots"--Vegetable
     Oils--Animal Fats--Bone Fat--Rosin._


Having described the most important and interesting oils and fats used
or suggested for use in the manufacture of soap, let us now consider
briefly the methods of bleaching and treating the raw materials, prior
to their transference to the soap-pan.

_Crude Palm Oil._--Of the various methods suggested for bleaching palm
oil, the bichromate process originated by Watts is undoubtedly the best.
The reaction may be expressed by the following equation, though in
practice it is necessary to use twice the amount of acid required by
theory:--

    K_{2}Cr_{2}O_{7} + 14HCl = 2KCl + Cr_{2}Cl_{6} + 7H_{2}O + 6Cl.

    6Cl + 3H_{2}O = 6HCl + 3O.

The palm oil, freed from solid impurities by melting and subsidence, is
placed in the bleaching tank, and washed with water containing a little
hydrochloric acid. Having allowed it to rest, and drawn off the liquor
and sediment (chiefly sand), the palm oil is ready for treatment with
the bleaching reagent, which consists of potassium bichromate and
commercial muriatic acid. For every ton of oil, 22 to 28 lb. potassium
bichromate and 45 to 60 lb. acid will be found sufficient to produce a
good bleached oil.

The best procedure is to act upon the colouring matter of the oil three
successive times, using in the first two treatments one-third of the
average of the figures just given, and in the final treatment an
appropriate quantity which can be easily gauged by the appearance of a
cooled sample of the oil.

The potassium bichromate is dissolved in hot water and added to the
crude palm oil, previously heated to 125° F. (52° C.), the requisite
amount of muriatic acid being then run in and the whole well agitated by
means of air. The bright red colour of the oil gradually changes to dark
brown, and soon becomes green. The action having proceeded for a few
minutes, agitation is stopped, and, after allowing to settle, the green
liquor is withdrawn.

When sufficiently bleached the oil is finally washed (without further
heating) with hot water (which may contain salt), to remove the last
traces of chrome liquor.

If the above operation is carried out carefully, the colouring matter
will be completely oxidised.

It is important, however, that the temperature should not be allowed to
rise above 130° F. (54° C.) during the bleaching of palm oil, otherwise
the resultant oil on saponification is apt to yield a soap of a "foxy"
colour. The bleached oil retains the characteristic violet odour of the
original oil.

It has been suggested to use dilute sulphuric acid, or a mixture of this
and common salt, in the place of muriatic acid in the above process.

_Crude Cotton-seed Oil._--The deep colouring matter of crude cotton-seed
oil, together with the mucilaginous and resinous principles, are removed
by refining with caustic soda lye.

The chief aim of the refiner is to remove these impurities without
saponifying any of the neutral oil. The percentage of free fatty acids
in the oil will determine the quantity of caustic lye required, which
must only be sufficient to remove this acidity.

Having determined the amount of free acidity, the quantity of caustic
soda lye necessary to neutralise it is diluted with water to 12° or 15°
Tw. (8° or 10° B.), and the refining process carried out in three
stages. The oil is placed in a suitable tank and heated by means of a
closed steam coil to 100° F. (38° C.), a third of the necessary weak
caustic soda lye added in a fine stream or by means of a sprinkler, and
the whole well agitated with a mechanical agitator or by blowing a
current of air through a pipe laid on the bottom of the tank.

Prolonged agitation with air has a tendency to oxidise the oil, which
increases its specific gravity and refractive index, and will be found
in the soap-pan to produce a reddish soap. As the treatment proceeds,
the temperature may be carefully raised, by means of the steam coil, to
120° F. (49° C.).

The first treatment having proceeded fifteen minutes, the contents of
the tank are allowed to rest; the settling should be prolonged as much
as possible, say overnight, to allow the impurities to precipitate well,
and carry down the least amount of entangled oil. Having withdrawn these
coloured "foots," the second portion of the weak caustic soda solution
is agitated with the partially refined oil, and, when the latter is
sufficiently treated, it is allowed to rest and the settled coloured
liquor drawn off as before. The oil is now ready for the final
treatment, which is performed in the same manner as the two previous
ones. On settling, a clear yellow oil separates.

If desired, the oil may be brightened and filtered, after refining to
produce a marketable article, but if it is being refined for own use in
the soap-house, this may be omitted.

The residue or "foots" produced during the refining of crude
cotton-seed oil, known in the trade as "mucilage," may be converted into
"soapstock" as mentioned in the preceding chapter, or decomposed by a
mineral acid and made into "black grease" ready for distillation by
superheated steam.

_Vegetable Oils._--The other vegetable oils come to the soap-maker's
hand in a refined condition; occasionally, however, it is desirable to
remove a portion of the free fatty acids, which treatment also causes
the colouring matter to be preciptated. This is effected by bringing the
oil and a weak solution of caustic lye into intimate contact. Cocoa-nut
oil is often treated in this manner. Sometimes it is only necessary to
well agitate the oil with 1-1/2 per cent. of its weight of a 12° Tw. (8°
B.) solution of caustic soda and allow to settle. The foots are utilised
in the soap-pan.

_Animal Fats._--Tallows are often greatly improved by the above alkaline
treatment at 165° F. (73° C.). It is one of the best methods and
possesses advantages over acid processes--the caustic soda removes the
free acid and bodies of aldehyde nature, which are most probably the
result of oxidation or polymerisation, whereas the neutral fat is not
attacked, and further, the alkaline foots can be used in the production
of soap.

_Bone fat_ often contains calcium (lime) salts, which are very
objectionable substances in a soap-pan. These impurities must be removed
by a treatment with hydrochloric or sulphuric acid. The former acid is
preferable, as the lime salt formed is readily soluble and easily
removed. The fat is agitated with a weak solution of acid in a
lead-lined tank by blowing in steam, and when the treatment is complete
and the waste liquor withdrawn, the last traces of acid are well washed
out of the liquid fat with hot water.

_Rosin._--Several methods have been suggested for bleaching rosin; in
some instances the constitution of the rosin is altered, and in others
the cost is too great or the process impracticable.

The aim of these processes must necessarily be the elimination of the
colouring matter without altering the original properties of the
substance. This is best carried out by converting the rosin into a
resinate of soda by boiling it with a solution of either caustic soda or
carbonated alkali. The process is commenced by heating 37 cwt. of 17°
Tw. (11° B.) caustic soda lye, and adding 20 cwt. of rosin, broken into
pieces, and continuing the boiling until all the resinate is
homogeneous, when an addition of 1-1/2 cwt. of salt is made and the
boiling prolonged a little. On resting, the coloured liquor rises to the
surface of the resinate, and may be siphoned off (or pumped away through
a skimmer pipe) and the resinate further washed with water containing a
little salt.

The treatment with carbonated alkali is performed in a similar manner. A
solution, consisting of 2-3/4 cwt. of soda ash (58°), in about four
times its weight of water, is heated and 20 cwt. of rosin, broken into
small pieces, added. The whole is heated by means of the open steam
coil, and care must be taken to avoid boiling over. Owing to the
liberation of CO_{2} gas, frothing takes place. A large number of
patents have been granted for the preparation of resinate of soda, and
many methods devised to obviate the boiling over. Some suggest mixing
the rosin and soda ash (or only a portion of the soda ash) prior to
dissolving in water; others saponify in a boiler connected with a trap
which returns the resinate to the pan and allows the carbonic-acid gas
to escape or to be collected.

With due precaution the method can be easily worked in open vessels,
and, using the above proportions, there will be sufficient uncombined
rosin remaining to allow the resultant product to be pumped into the
soap with which it is intended to intermix it, where it will be finally
saponified thoroughly.

The salt required, which, in the example given, would be 1-1/2 cwt., may
be added to the solution prior to the addition of rosin or sprinkled in
towards the finish of the boiling. When the whole has been sufficiently
boiled and allowed to rest, the liquor containing the colouring matter
will float over the resinate, and, after removal, may be replaced by
another washing.

Many other methods have been suggested for the bleaching, refining and
treatment of materials intended for saponification, but the above
practical processes are successfully employed.

All fats and oils after being melted by the aid of steam must be allowed
to thoroughly settle, and the condensed water and impurities withdrawn
through a trap arrangement for collecting the fatty matter. The molten
settled fatty materials _en route_ to the soap-pan should be passed
through sieves sufficiently fine to free them from suspended matter.



CHAPTER V.

SOAP-MAKING.

     _Classification of Soaps--Direct Combination of Fatty Acids
     with Alkali--Cold Process Soaps--Saponification under Increased
     or Diminished Pressure--Soft Soap--Marine Soap--Hydrated Soaps,
     Smooth and Marbled--Pasting or Saponification--Graining
     Out--Boiling on Strength--Fitting--Curd Soaps--Curd
     Mottled--Blue and Grey Mottled Soaps--Milling Base--Yellow
     Household Soaps--Resting of Pans and Settling of
     Soap--Utilisation of Nigres--Transparent Soaps--Saponifying
     Mineral Oil--Electrical Production of Soap._


Soaps are generally divided into two classes and designated "hard," and
"soft," the former being the soda salts, and the latter potash salts, of
the fatty acids contained in the material used.

According to their methods of manufacture, soaps may, however, be more
conveniently classified, thus:--

(A) Direct combination of fatty acids with alkali.

(B) Treatment of fat with definite amount of alkali and no separation of
waste lye.

(C) Treatment of fat with indefinite amount of alkali and no separation
of waste lye.

(D) Treatment of fat with indefinite amount of alkali and separation of
waste lye.

(A) _Direct Combination of Fatty Acids with Alkali._--This method
consists in the complete saturation of fatty acids with alkali, and
permits of the use of the deglycerised products mentioned in chapter
ii., section 2, and of carbonated alkalies or caustic soda or potash.
Fatty acids are readily saponified with caustic soda or caustic potash
of all strengths.

The saponification by means of carbonated alkali may be performed in an
open vat containing a steam coil, or in a pan provided with a removable
agitator.

It is usual to take soda ash (58°), amounting to 19 per cent. of the
weight of fatty acids to be saponified, and dissolve it in water by the
aid of steam until the density of the solution is 53° Tw. (30° B.); then
bring to the boil, and, whilst boiling, add the molten fatty acids
slowly, but not continuously.

Combination takes place immediately with evolution of carbonic acid gas,
which causes the contents of the vat or pan to swell, and frequently to
boil over. The use of the agitator, or the cessation of the flow of
fatty acids, will sometimes tend to prevent the boiling over. It is
imperative that the steam should not be checked but boiling continued
as vigorously as possible until all the alkali has been absorbed and the
gas driven off.

The use of air to replace steam in expelling the carbonic acid gas has
been patented (Fr. Pat. 333,974, 1903).

A better method of procedure, however, is to commence with a solution of
64° Tw. (35° B.) density, made from half the requisite soda ash (9-1/2
per cent.), and when this amount of alkali has all been taken up by the
fatty acids (which have been added gradually and with continuous
boiling), the remaining quantity of soda ash is added in a dry state,
being sprinkled over each further addition of fatty acid.

This allows the process to be more easily controlled and boiling over is
avoided.

It is essential that the boiling by steam should be well maintained
throughout the process until all carbonic acid gas has been thoroughly
expelled; when that point is reached, the steam may be lessened and the
contents of the vat or pan gently boiled "on strength" with a little
caustic lye until it ceases to absorb caustic alkali, the soap being
finished in the manner described under (D).

It is extremely difficult to prevent discoloration of fatty acids, hence
the products of saponification in this way do not compare favourably in
appearance with those produced from the original neutral oil or fat.

(B) _Treatment of Fat with Definite Amount of Alkali and no Separation
of Waste Lye._--Cold-process soap is a type of this class, and its
method of production is based upon the characteristic property which the
glycerides of the lower fatty acids (members of the cocoa-nut-oil class)
possess of readily combining with a strong caustic soda solution at a
low temperature, and evolving sufficient heat to complete the
saponification.

Sometimes tallow, lard, cotton-seed oil, palm oil and even castor oil
are used in admixture with cocoa-nut oil. The process for such soap is
the same as when cocoa-nut oil is employed alone, with the slight
alteration in temperature necessary to render the fats liquid, and the
amount of caustic lye required will be less. Soaps made of these blends
closely resemble, in appearance, milled toilet soaps. In such mixtures
the glycerides of the lower fatty acids commence the saponification, and
by means of the heat generated induce the other materials, which alone
would saponify with difficulty or only with the application of heat, to
follow suit.

It is necessary to use high grade materials; the oils and fats should be
free from excess of acidity, to which many of the defects of
cold-process soaps may be traced. Owing to the rapidity with which free
acidity is neutralised by caustic soda, granules of soap are formed,
which in the presence of strong caustic lye are "grained out" and
difficult to remove without increasing the heat; the soap will thus tend
to become thick and gritty and sometimes discoloured.

The caustic lye should be made from the purest caustic soda, containing
as little carbonate as possible; the water used for dissolving or
diluting the caustic soda should be soft (_i.e._, free from calcium and
magnesium salts), and all the materials carefully freed from particles
of dirt and fibre by straining.

The temperature, which, of course, must vary with the season, should be
as low as is consistent with fluidity, and for cocoa-nut oil alone may
be 75° F. (24° C.), but in mixtures containing tallow 100° to 120° F.
(38° to 49° C.).

The process is generally carried out as follows:--

The fluid cocoa-nut oil is stirred in a suitable vessel with half its
weight of 71.4° Tw. (38° B.) caustic soda lye at the same temperature,
and, when thoroughly mixed, the pan is covered and allowed to rest. It
is imperative that the oils and fats and caustic lye should be
intimately incorporated or emulsified. The agitating may be done
mechanically, there being several machines specially constructed for the
purpose. In one of the latest designs the caustic lye is delivered
through a pipe which rotates with the stirring gear, and the whole is
driven by means of a motor.

The agitation being complete, chemical action takes place with the
generation of heat, and finally results in the saponification of the
fats.

At first the contents of the pan are thin, but in a few hours they
become a solid mass. As the process advances the edges of the soap
become more transparent, and when the transparency has extended to the
whole mass, the soap is ready, after perfuming, to be framed and
crutched.

The admixture of a little caustic potash with the caustic soda greatly
improves the appearance of the resultant product, which is smoother and
milder.

The glycerine liberated during the saponification is retained in the
soap.

Although it is possible, with care, to produce neutral soaps of good
appearance and firm touch by this method, cold-process soaps are very
liable to contain both free alkali and unsaponified fat, and have now
fallen considerably into disrepute.

_Saponification under Increased or Diminished Pressure._--Soaps made by
boiling fats and oils, under pressure and _in vacuo_, with the exact
quantity of caustic soda necessary for complete combination, belong also
to this class. Amongst the many attempts which have at various times
been made to shorten the process of soap-making may be mentioned
Haywood's Patent No. 759, 1901, and Jourdan's French Patent No. 339,154,
1903.

In the former, saponification is carried out in a steam-jacketed vacuum
chamber provided with an elaborate arrangement of stirrers; in the other
process fat is allowed to fall in a thin stream into the amount of lye
required for saponification, previously placed in the saponification
vessel, which is provided with stirring gear.

When the quantities have been added, steam is admitted and
saponification proceeds.

(C) _Treatment of Fat with Indefinite Amount of Alkali and no Separation
of Waste Lye._--_Soft soap_ is representative of this class. The
vegetable fluid oils (linseed, olive, cotton-seed, maize) are for the
most part used in making this soap, though occasionally bone fats and
tallow are employed. Rosin is sometimes added, the proportion ranging,
according to the grade of soap required, from 5 to 15 per cent. of the
fatty matter.

The Soft Soap Manufacturers' Convention of Holland stipulate that the
materials used in soft-soap making must not contain more than 5 per
cent. rosin; it is also interesting to note that a patent has been
granted (Eng. Pat. 17,278, 1900) for the manufacture of soft soap from
material containing 50 per cent. rosin.

Fish or marine animal oils--whale, seal, etc., once largely used as raw
material for soft soap, have been superseded by vegetable oils.

The materials must be varied according to the season; during hot
weather, more body with a less tendency to separate is given by the
introduction of oils and fats richer in stearine; these materials also
induce "figging".

The most important material, however, is the caustic potash lye which
should average 40° Tw. (24° B.), _i.e._, if a weak solution is used to
commence saponification, a stronger lye must be afterwards employed to
avoid excess of water in the soap, and these average 40° Tw. (24° B.).
The potash lye must contain carbonates, which help to give transparency
to the resultant soap. If the lye is somewhat deficient in carbonates,
they may be added in the form of a solution of refined pearl ash
(potassium carbonate).

Caustic soda lye is sometimes admixed, to the extent of one-fourth, with
potash lye to keep the soap firmer during hot weather, but it requires
great care, as a slight excess of soda gives soft soap a bad appearance
and a tendency to separate.

The process is commenced by running fatty matter and weak potash lyes
into the pan or copper, and boiling together, whilst the introduction of
oil and potash lye is continued.

The saponification commences when an emulsion forms, and the lye is then
run in more quickly to prevent the mass thickening.

Having added sufficient "strength" for complete saponification, the
boiling is continued until the soap becomes clear.

The condition of the soap is judged by observing the behaviour of a
small sample taken from the pan and dropped on glass or iron. If the
soap is satisfactory it will set firm, have a short texture and slightly
opaque edge, and be quite clear when held towards the light. If the
cooled sample draws out in threads, there is an excess of water present.
If an opaque edge appears and vanishes, the soap requires more lye. If
the sample is turbid and somewhat white, the soap is too alkaline and
needs more oil.

The glycerine liberated during saponification is contained in the soap
and no doubt plays a part in the production of transparency.

_Hydrated soaps_, both smooth and marbled, are included in this
classification, but are _soda_ soaps. Soap made from cocoa-nut oil and
palm-kernel oil will admit of the incorporation of large quantities of a
solution of either salt, carbonate of soda, or silicate of soda, without
separation, and will retain its firmness. These materials are,
therefore, particularly adapted for the manufacture of marine soaps,
which often contain as much as 80 per cent. of water, and, being soluble
in brine, are capable of use in sea-water. For the same reason,
cocoa-nut oil enters largely into the constitution of hydrated soaps,
but the desired yield or grade of soap allows of a variation in the
choice of materials. Whilst marine soap, for example, is usually made
from cocoa-nut oil or palm-kernel oil only, a charge of 2/3 cocoa-nut
oil and 1/3 tallow, or even 2/3 tallow and 1/3 cocoa-nut oil, will
produce a paste which can carry the solutions of silicate, carbonate,
and salt without separation, and yield a smooth, firm soap.

The fatty materials, carefully strained and freed from particles of dirt
and fibre, are boiled with weak caustic soda lye until combination has
taken place. Saponification being complete, the solution of salt is
added, then the carbonate of soda solution, and finally the silicate of
soda solution, after which the soap is boiled. When thoroughly mixed,
steam is shut off, and the soap is ready for framing.

The marbled hydrated soap is made from cocoa-nut oil or a mixture of
palm-kernel oil and cocoa-nut oil with the aid of caustic soda lye
32-1/2° Tw. (20° B.). As soon as saponification is complete, the brine
and carbonate of soda solution are added, and the pan allowed to rest.

The soap is then carefully tasted as to its suitability for marbling by
taking samples and mixing with the colouring solution (ultramarine mixed
with water or silicate of soda solution). If the sample becomes blue
throughout, the soap is too alkaline; if the colour is precipitated, the
soap is deficient in alkali. The right point has been reached when the
marbling is distributed evenly. Having thus ascertained the condition of
the pan, and corrected it if necessary, the colour, mixed in water or in
silicate of soda solution, is added and the soap framed.

(D) _Treatment of Fat with Indefinite Amount of Alkali and Separation of
Waste Lye._--This is the most general method of soap-making. The various
operations are:--

          (_a_) Pasting or saponification.
          (_b_) Graining out or separation.
          (_c_) Boiling on strength.

And in the case of milling soap base and household soaps,

          (_d_) Fitting.

(_a_) _Pasting or Saponification._--The melted fats and oils are
introduced into the soap-pan and boiled by means of open steam with a
caustic soda lye 14° to 23.5° Tw. (10° to 15° B.). Whether the fatty
matters and alkali are run into the pan simultaneously or separately is
immaterial, provided the alkali is not added in sufficient excess to
retard the union.

The commencement of the saponification is denoted by the formation of an
emulsion. Sometimes it is difficult to start the saponification; the
presence of soap will often assist this by emulsifying the fat and thus
bringing it into intimate contact with the caustic soda solution.

When the action has started, caustic soda lye of a greater density, 29°
to 33° Tw. (18° to 20° B.), is frequently added, with continued boiling,
in small quantities as long as it is being absorbed, which is
ascertained by taking out samples from time to time and examining them.

There should be no greasiness in the sample, but when pressed between
finger and thumb it must be firm and dry.

Boiling is continued until the faint caustic taste on applying the
cooled sample to the tongue is permanent, when it is ready for "graining
out". The pasty mass now consists of the soda salts of the fat (as
imperfect soap, probably containing emulsified diglycerides and
monoglycerides), together with water, in which is dissolved the
glycerine formed by the union of the liberated glyceryl radicle from the
fat with the hydroxyl radicle of the caustic soda, and any slight excess
of caustic soda and carbonates. The object of the next operation is to
separate this water (spent lye) from the soap.

(_b_) _Graining Out or Separation._--This is brought about by the use of
common salt, in a dry form or in solution as brine, or by caustic soda
lye. Whilst the soap is boiling, the salt is spread uniformly over its
surface, or brine 40° Tw. (24° B.) is run in, and the whole well boiled
together. The soap must be thoroughly boiled after each addition of
salt, and care taken that too large a quantity is not added at once.

As the soap is gradually thrown out of solution, it loses its smooth
transparent appearance, and becomes opaque and granular.

When a sample, taken out on a wooden trowel, consists of distinct grains
of soap and a liquid portion, which will easily separate, sufficient
salt or brine has been added; the boiling is stopped and the spent lye
allowed to settle out, whilst the soap remains on the surface as a more
or less thick mass.

The separated spent lye consists of a solution of common salt,
glycerine, and alkaline salts; the preparation of crude glycerine
therefrom is considered in chapter ix.

The degree of separation of water (spent lye) depends upon the amount of
precipitant used. The aim is to obtain a maximum amount of spent lye
separated by the use of a minimum quantity of salt.

The amount of salt required for "graining out" varies with the raw
material used. A tallow soap is the most easily grained, more salt is
required for cotton-seed oil soap, whereas soaps made from cocoa-nut and
palm-kernel oils require very large amounts of salt to grain out
thoroughly. Owing to the solubility in weak brine of these latter soaps,
it is preferable to grain them with caustic soda lye. This is effected
by adding, during boiling, sufficient caustic lye (32-1/2° Tw., 20° B.)
to produce the separation of the granules of soap. The whole is allowed
to rest; the separated half-spent lye is withdrawn and may be used for
the pasting of fresh materials.

After the removal of the settled lye, the grained mass is boiled with
sufficient water to dissolve the grain and make it smooth ("close" it),
and is now ready for the next operation of "boiling on strength".

(_c_) _Boiling on Strength or Clear Boiling._--This is the most
important operation and is often termed "making the soap". The object is
to harden the soap and to ensure complete saponification.

Caustic soda lye (32-1/2° Tw., 20° B.) is gradually added until the soap
is again opened or grained, and boiling continued by the use of the dry
steam coil. As soon as the caustic soda lye is absorbed, another portion
is slowly added, and this is continued until the caustic soda or
"strength" remains permanent and the soapy mass, refusing to absorb
more, is thrown out of solution and grained. The granular mass will boil
steadily, and the boiling should be prolonged, as the last traces of
neutral oil are difficult to completely saturate with alkali. Thorough
saponification takes place gradually, and the operation cannot be
hurried; special care has to be bestowed upon this operation to effect
the complete combination of fat and alkali.

After resting for several hours, half-spent lye settles to the bottom of
the pan. In the case of yellow soaps or milling bases the settled lye is
removed to a suitable receptacle and reserved for use in the
saponification of other material, and the soap is then ready for the
final operation of "fitting".

(_d_) _Fitting._--If the operations just described have been properly
performed, the fitting should present no difficulty. The soap is boiled
with open steam, and water added until the desired degree of closing is
attained. As the water is thoroughly intermixed throughout the mass the
thick paste gradually becomes reduced to a smooth, thin consistence.
Samples are tested from time to time as to their behaviour in dropping
off a hot trowel held sideways; the thin layer should drop off in two or
three flakes and leave the surface of the trowel clean and dry. The soap
is then in a condition to allow the impurities to gravitate. According
to the required soap, the fit may be "coarse" ("open") when the flakes
drop off the trowel readily, or "fine" ("close") when the flakes only
leave the trowel with difficulty.

If the dilution with water has been allowed to proceed too far, and too
fine a fit is produced, which would be denoted by the layer of soap not
leaving the trowel, a little caustic lye or brine may be very carefully
added and the whole well boiled until the desired condition is obtained.

A good pressure of steam is now applied to the pan, causing the contents
to swell as high as possible, this greatly facilitating the settling of
impurities; steam is then turned off, the pan covered, and the boil
allowed to rest for several days.

The art of fitting consists in leaving the contents of the pan in such a
condition that, on standing, all the impurities precipitate, and the
settled soap, containing the correct amount of water, is clear and
bright.

The above is a general practical outline of the ordinary soap-boiling
process. It may be modified or slightly altered according to the fancy
of the individual soap-maker or the particular material it is desired to
use. Fats and oils not only vary in the amount of alkali they absorb
during saponification, but also differ in the strength of the alkali
they require. Tallow and palm oil require lye of a density of 15° to 18°
Tw. (10° to 12° B.), but cocoa-nut oil alone would not saponify unless
the lye was more concentrated, 33° to 42° Tw. (20° to 25° B.).
Cotton-seed oil requires weak lyes for saponification, and, being
difficult to saponify alone even with prolonged boiling, is generally
mixed with animal fat.

When fats are mixed together, however, their varying alkali requirements
become modified, and once the saponification is begun with weak lye,
other materials are induced to take up alkali of a strength with which
alone they would not combine.

It is considered the best procedure to commence the pasting or
saponification with weak lye.

In order to economise tank space, it is the general practice to store
strong caustic lye (60° to 70° Tw., 33° to 37° B.) and to dilute it as
it is being added to the soap-pan by the simultaneous addition of water.

Many manufacturers give all their soap a "brine wash" to remove the last
traces of glycerine and free the soap from carbonates. This operation
takes place prior to "fitting"; sufficient water is added to the boiling
soap to "close" it and then brine is run in to "grain" it.

After resting, the liquor is withdrawn.

Having described the necessary operations in general, we will now
consider their application to the preparation of various kinds of hard
soap.

_Curd Soaps._--Tallow is largely used in the manufacture of white curd
soaps, but cocoa-nut oil sometimes enters into their composition.

The first three operations above described, _viz._, pasting, graining
out, and boiling on strength, are proceeded with; the clear boiling by
means of a closed steam coil is continued until the "head" is boiled out
and the soap is free from froth. A sample taken and cooled should be
hard. Boiling is then stopped, and, after covering, the pan is allowed
to rest for eight to ten hours, when the soap is ready for filling into
frames, where it is crutched until perfectly smooth.

_Curd mottled_ is usually made from melted kitchen stuff and bone
grease.

Its preparation is substantially the same as for curd soap, but the
clear boiling is not carried so far. The art of curd mottled soap-making
lies in the boiling. If boiled too long the mottling will not form
properly, and, on the other hand, insufficient boiling will cause the
soap to contain an excess of entangled lye. Having boiled it to its
correct concentration the pan is allowed to rest about two hours, after
which the soap is ready for framing, which should be done expeditiously
and the frames covered up.

Some lye, containing the impurities from the fats used, remains in the
interstices of the curd, unable to sink, and as the soap cools it is
enclosed and forms the mottling. The mottling may, therefore, be
considered as a crystallisation of the soap, in which the impurity forms
the colour.

_Blue and Grey Mottled Soaps._--These are silicated or liquored soaps in
which the natural mottling, due to the impure materials used in the
early days of soap-making, is imitated by artificial mottling, and are,
consequently, entirely different to curd mottled soaps.

The materials employed in making mottled soap comprise bleached palm
oil, tallow, bone fat, cocoa-nut oil, palm-kernel oil, cotton-seed oil,
and, in some instances, rosin.

The choice of a charge will naturally depend upon the cost; the property
of absorbing a large amount of liquor, which is characteristic of soaps
made from cocoa-nut oil and palm-kernel oil, is taken advantage of, as
are also the physical properties of the various fats and oils, with a
view to the crystallisation of the resultant soap and the development of
the mottle. The fat is saponified, grained and boiled on strength, as
previously described. After withdrawing the half-spent lye, the soap is
just closed by boiling with water, and is then ready for the silicate or
other saline additions.

Soap intended to be liquored with silicate of soda should be distinctly
strong in free alkali; the crystalline nature of the soap is increased
thereby, and the mottled effect intensified. Some makers, however, fit
the soap coarsely and allow a nigre to deposit; then, after removing the
nigre, or transferring the settled soap to another copper, containing
scraps of mottled soap, get the soap into a condition for mottling, and
add the silicate of soda solution. To every 1 cwt. of soap, 28 lb. of
silicate of soda solution, 32-1/2° Tw. (20° B.) is added, whilst
boiling; the strength of the silicate solution, however, will depend
upon the proportion of cocoa-nut oil and palm-kernel oil present in the
charge. Many soap-makers use 20° Tw. (13° B.) (cold) silicate solution,
whilst others prefer 140° Tw. (59.5° B.), with the gradual addition of
water to the soap, kept boiling, until the product is in the correct
mottling condition, and others, again, use bleach liquor, soda crystals,
pearl ash, and salt, together with silicate solution.

Considerable skill and experience is necessary to discern when the soap
acquires the correct mottling state. It should drop off the spatula in
large thick flakes, take considerable time to set, and the surface
should not be glossy.

When this mottling condition has been obtained, the colouring matter,
which would be ultramarine for the blue mottled and manganese dioxide
for the grey mottled soap (3-4 lb. ultramarine or 1-3 lb. manganese
dioxide being sufficient for 1 ton of soap), is mixed with a little
water and added to the boiling soap--the boiling is continued until all
is thoroughly amalgamated, and when the steam is shut off the contents
of the pan are ready for cleansing.

Mottled soap is run into wooden frames, which, when full, are covered
over and allowed to cool very gradually. On cooling slowly, large
crystals are produced which result in a distinct bold mottle; if the
cooling is too rapid, a small crystal is obtained and the mottle is not
distributed, resulting in either a small mottle, or no mottle at all,
and merely a general coloration. In fact, the entire art of mottling
soap consists in properly balancing the saline solutions and colouring
matter, so that the latter is properly distributed throughout the soap,
and does not either separate in coloured masses at the bottom of the
frame, or uniformly colour the whole mass.

A sample of the soap should test 45 per cent. fatty acids, and the
amount of salt would range from 1/2 to 1 per cent.

Some of the English mottled soaps, especially those made from materials
which give a yellow-coloured ground, are bleached by soaking in brine,
or pickling in brine containing 2 per cent. of bleach liquor. The
resultant soap has a white ground and is firm. The bleach liquor may be
made by mixing 1 cwt. bleaching powder with 10 cwts. of soda ash
solution (15° Tw., 10° B.), allowing to settle, and using the clear
liquid, or by mixing 2 parts soda ash solution with 1 part of bleaching
powder solution, both solutions being 30° Tw. (18.8° B.).

_Milling-base._--The materials generally used are tallows and cocoa-nut
oils of the finest quality. The tallow is thoroughly saponified first,
and the graining is performed by the aid of caustic soda lye in
preference to salt. The half-spent lyes are withdrawn, and the cocoa-nut
oil added to the pan. This is saponified, and when the saponification is
complete, "boiling-on-strength" is proceeded with. Special care should
be devoted to the "boiling-on-strength" operation--its value in good
soap-making cannot be over-rated--and perfect saponification must be
ensured. The half-spent lyes are allowed to deposit during the night,
and the soap must be carefully examined next morning to ascertain if any
alkali has been absorbed. If the caustic taste is permanent the
strengthening operation is complete, but should any caustic have been
absorbed, further addition of alkali must be made and the boiling
continued. These remarks apply equally to all soaps.

The soap, when ready, is fitted.

Bleached palm oil, olive oil, castor oil and lard are also employed in
the production of special milling soap bases, a palm oil soap being
specially suitable for the production of a violet-scented toilet soap.

_Yellow Household Soaps._ (_a_) _Bar Soaps._--These are made from tallow
with an admixture of from 15-25 per cent. rosin. The best quality is
known in the South and West of England as Primrose Soap, but is
designated in the North of England by such names as Golden Pale,
Imperial Pale, Gold Medal Pale, etc. Tallow alone produces a very hard
soap of inferior lathering qualities; but rosin combines with alkali to
form a soft body, which, although not a soap in the strict sense of the
term, is readily soluble in water, and in admixture with the durable
tallow soap renders it more soluble in water and thereby increases its
lathering properties.

The rosin may be added to the soap-pan after a previous partial
saponification with soda ash, and removal of colouring matter, and
finally saponified with caustic soda lye, or, as is more generally
adopted, as a rosin change. The pan is opened with caustic soda lye and
saturation of the rosin takes place rapidly; when completely saponified
it is grained with salt, and the coloured lye allowed to deposit and
finally withdrawn.

The four operations already detailed apply to this soap.

Cheaper pale soaps may be made from lower grades of tallow and rosin and
are generally silicated.

(_b_) _Tablet or Washer Type._--A demand has arisen for soap of free
lathering qualities, which has become very popular for general household
use. This soap is usually made from a mixture of cotton-seed oil,
tallow, and cocoa-nut oil, with a varying amount of rosin. The tallow
yields firmness and durability whilst the other constituents all assist
in the more ready production of a copious lather.

As to what amount of rosin can be used to yield a finished soap of
sufficient body and satisfactory colour, this naturally depends upon the
grade of raw material at the soap-makers' disposal. Those fats and oils
which yield firm soaps, will, of course, allow a greater proportion of
rosin to be incorporated with them than materials producing soaps of
less body. Rosin imparts softness to a soap, and also colour.

This is a fitted soap and full details of manufacture have already been
given.

Cheaper soaps are produced from lower grade materials hardened with
alkaline solutions.

_Resting of Pans and Settling of Soap._--The fitted soap is allowed to
settle from four to six days. The period allowed for resting is
influenced, however, not only by the size of the boil, and the season,
but also by the composition of the soap, for if the base has been made
from firm stock it is liable to cool quicker than a soap produced from
soft-bodied materials.

On subsidence, the contents of the pan will have divided into the
following:--

First. On top, a thin crust of soap, with perhaps a little light
coloured fob, which is returned to the pan after the removal of the good
soap.

Second. The good settled soap, testing 62-63 per cent. fatty acids. The
subject of removing and treatment of this layer is fully dealt with in
the next chapter.

Third. A layer of darker weak soap, termed "nigre," which on an average
tests 33 per cent. fatty acids, and, according to the particular fit
employed, will amount to from 15-20 per cent. of the total quantity of
soap in the pan.

The quantity of nigre may vary not only with the amount of water added
during finishing, but is also influenced by the amount of caustic alkali
remaining in the soap paste prior to fitting. If the free caustic
alkali-content is high, the soap will require a large amount of water to
attain the desired fit. This water renders the caustic into a lye
sufficiently weak to dissolve a quantity of soap, consequently, as the
"nigre" is a weak solution of soap together with any excess of alkali
(caustic or carbonate) and salt which gravitates during the settling,
the quantity is increased.

Fourth. A solution containing alkaline salts, mostly carbonates and
chlorides, with a little caustic.

The amount of the layer is very variable, and doubtless, under certain
physical conditions, this liquor has separated from the nigre.

_Utilisation of Nigres._--The nigres are boiled and the liquor separated
by graining with salt. Nigre may be utilised in various ways.

(1) It may be used several times with new materials. This particularly
refers to soaps of the "Washer" type. The colour of the nigre will
determine the number of times it can be employed.

(2) It may be incorporated with a soap of a lower grade than the one
from which it was obtained. In this case a system is generally adopted;
for example, soap of the best quality is made in a clean pan, the nigre
remaining is worked up with fresh material for soap of the next quality,
the nigre from that boil, in its turn, is admixed with a charge to
produce a batch of third quality, and the deposited nigre from this is
again used for a fourth quality soap--the nigre obtained from this
latter boil would probably be transferred into the cheapened "washer" or
perhaps if it was dark in colour into the brown soap-pan.

(3) The nigre may be fitted and produce a soap similar to the original
soap from which it was deposited. It is advisable to saponify a little
fat with it.

(4) Nigres from several boils of the same kind of soap can be collected,
boiled, and fitted. The settled portion may be incorporated with a new
charging to keep the resultant soap uniform in colour--unless this is
done, the difference in colour between boils from new materials alone,
and those containing nigre, is very noticeable. The nigre settled from
this fitted nigre boil would be utilised in brown soap.

(5) According to its colour, and consistence, a nigre may be suitable
for the production of disinfectant, or cold-water soaps.

(6) Nigre may be bleached by treatment with a 20 per cent. solution of
stannous chloride--1 cwt. of this solution (previously heated) is
sufficient to bleach 20 tons of nigre.

_Transparent Soaps._--The production of transparent soaps has recently
been fully studied, from a theoretical point of view, by Richardson
(_J. Amer. Chem. Soc._, 1908, pp. 414-20), who concludes that the
function of substances inducing transparency, is to produce a jelly and
retard crystallisation.

The old-fashioned transparent soap is prepared by dissolving, previously
dried, genuine yellow soap in alcohol, and allowing the insoluble saline
impurities to be deposited and removed. The alcoholic soap solution is
then placed in a distillation apparatus, or the pan containing the
solution is attached by means of a still head to a condenser, and the
alcohol distilled, condensed and regained. The remaining liquid soap,
which may be coloured and perfumed, is run into frames and allowed to
solidify.

The resultant mass is somewhat turbid, but after storage in a room at
95° F. (35° C.) for several months, becomes transparent.

The formation of the transparency is sometimes assisted and hastened by
the addition of glycerine or a solution of cane-sugar.

A patent has been granted to A. Ruch (Fr. Pat. 327,293, 1902) for the
manufacture of transparent glycerine soap by heating in a closed vessel
fatty acids together with the requisite quantity of alcoholic caustic
soda solution necessary for saponification, and cooling the resultant
soap. It is also proposed to add sugar solution.

Cheaper qualities of transparent soaps are made by the cold process with
or without the aid of alcohol and castor oil, and with the assistance of
glycerine or cane-sugar.

With the continual demand for cheaper production, sugar solution has
gradually, in conjunction with castor oil, which produces transparency,
superseded the use of alcohol and glycerine.

For a small batch, 56 lb. Cochin cocoa-nut oil and 56 lb. sweet edible
tallow may be taken, melted at 130° F. (54° C.), and carefully strained
into a small steam-jacketed pan. It is imperative that the materials
should be of the highest quality and perfectly clean. Twenty-three lb.
of pure glycerine and 56 lb. of bright caustic soda solution made from
high grade caustic and having a density of 72° Tw. (38° B.) are crutched
into the fat; the alcohol, which would be 45 lb. in this example, is
then added. The whole must be most intimately incorporated, and the pan
covered and allowed to rest for one hour or one and a half hours.
Saponification should ensue.

To produce a transparent glycerine soap with the aid of castor oil, and
with or without the use of alcohol, the following is the procedure:--

Cochin cocoa-nut oil, sweet edible tallow, and castor oil, of each 56
lb. are taken, warmed to 130° F. (54° C.), and carefully strained into
the jacketed pan. If it is desired to use glycerine and cane sugar
solution, and no alcohol, the glycerine (25 lb.) is now stirred into the
fats together with the requisite (83 lb.) caustic soda solution 72° Tw.
(38° B.). If it is intended to use alcohol and sugar, and no glycerine,
the latter is replaced by 47 lb. of alcohol, and added after the
incorporation of the caustic soda lye.

The whole being thoroughly crutched, the pan is covered and
saponification allowed to proceed for one hour or one and a half hours.
Should the saponification for some reason be retarded, a little steam
may be very cautiously admitted to the jacket of the pan, the mass well
crutched until the reaction commences, and the whole allowed to rest the
specified time.

Whilst saponification is proceeding, the "sugar solution" is prepared by
dissolving 50 lb. cane sugar in 50 lb. water, at 168° F. (76° C.), to
which may be added 5 lb. soda crystals, and any necessary colouring
matter. The water used for this solution should be as soft as possible,
as hard water is liable to produce opaque streaks of lime soap.

It is absolutely necessary before proceeding further to ensure that
saponification is complete. A greasy, soft feel and the presence of
"strength" (caustic) would denote incomplete saponification--this can
only be remedied by further heating and crutching. Deficiency of caustic
alkali should also be avoided, and, if more lye is required, great care
must be exercised in its addition.

Saponification being completed, the sugar solution is carefully and
gradually crutched into the soap; when the contents of the pan have
become a homogeneous and syrupy mass, the crutching is discontinued, and
the pan is covered for one hour. The heat of the soap in the pan should
not exceed 170° F. (77° C.).

Having rested the necessary period, the soap will have a slight froth on
the surface, but will be clear underneath and appear dark. Samples may
now be withdrawn, cooled, and examined prior to framing. If the process
has been successfully performed the soap will be firm and transparent,
of uniform colour, and possess only a faintly alkaline taste.

If the sample be firm but opaque, more sugar solution is required; this
should be added very carefully whilst crutching, an excess being
specially guarded against. If the sample be soft, although transparent,
and the alkaline taste not too pronounced, the soap evidently contains
an excess of water, which may be remedied by the addition of a small
quantity of soda ash; too much soda ash (carbonates) must be avoided,
lest it should produce efflorescence.

Having examined the soap and found it to be correct, or having remedied
its defects, the soap in the pan is allowed to cool to 145° F. (63° C.)
and perfume added. The soap is now quickly filled into narrow frames and
allowed to cool rapidly.

The blocks of soap should not be stripped until quite cold throughout,
and they should be allowed to stand open for a while before slabbing.
When freshly cut into tablets, the soap may appear somewhat turbid, but
the brightness comes with the exposure it will receive prior to stamping
and wrapping.

_Saponifying Mineral Oil._--This sounds somewhat incongruous, as mineral
oil is entirely unsaponifiable. Most of the suggestions for this purpose
consist of the incorporation of mineral oil, or mineral oil emulsified
by aid of Quillaia bark, with a cocoa-nut oil soap, and in all these
instances the hydrocarbon merely exists in suspension.

G. Reale (Fr. Pat. 321,510, 1902), however, proposes to heat mineral oil
together with spermaceti and strong alkali, and states that he
transforms the hydrocarbons into alcohols, and these, absorbing oxygen,
become fatty acids, which are converted into soap by means of the
alkali.

In this connection may be quoted the interesting work of Zelinsky
(_Russ. Phys. Chem. Ges. Zeits. Angew. Chem._, 1903, 37). He obtained
substances, by acting with carbon dioxide upon magnesia compounds of
chlorinated fractions of petroleum, which when decomposed by dilute
sulphuric acid, yielded various organic acids. One of these acids on
heating with glycerine formed tri-octin, which had the properties of a
fat.

Dr. Engler, in confirmation of the theory of the animal origin of some
petroleums, obtained what might be described as petroleum (for it
contained almost all the hydrocarbons present in the natural mineral
oil) by distilling animal fats and oils under pressure.

_Electrical Production of Soap._--Attempts have been made to produce
soap electrically by Messrs. Nodon, Brettonneau and Shee (Eng. Pat.
22,129, 1897), and also by Messrs. Merry and Noble (Eng. Pat. 2,372,
1900).

In the former patent, a mixture of soda-lye and fat is agitated by
electricity at a temperature of 194°-212° F. (90°-100° C.), while in the
latter caustic alkali is electrolytically produced from brine, and
deposited on wire-netting in the presence of fat, which is thereby
saponified.



CHAPTER VI.

TREATMENT OF SETTLED SOAP.

     _Cleansing--Crutching--Liquoring of
     Soaps--Filling--Neutralising, Colouring and
     Perfuming--Disinfectant Soaps--Framing--Slabbing--Barring--Open
     and Close Piling--Drying--Stamping--Cooling._


_Cleansing._--After completion of saponification, and allowing the
contents of the pan to settle into the various layers, as described in
the preceding chapter, the actual soap, forming the second layer, is now
transferred to the frames, this being generally termed "cleansing" the
soap. The thin crust or layer at the top of the pan is gently removed,
and the soap may be either ladled out and conveyed to the frames, or
withdrawn by the aid of a pump from above the nigre through a skimmer
(Fig. 1), and pipe, attached by means of a swivel joint (Fig. 2) (which
allows the skimmer pipe to be raised or lowered at will by means of a
winch, Fig. 3), to a pipe fitted in the side of the pan as fully shown
in Fig. 4, or the removal may be performed by gravitation through some
mechanical device from the side of the copper.

[Illustration: FIG. 1.--Skimmer, with flange for attachment to
skimmer-pipe.]

Every precaution is taken to avoid the presence of nigre in the soap
being cleansed.

[Illustration: FIG. 2.--Swivel-joint.]

The temperature at which soap may be cleansed depends on the particular
grade--soaps requiring to be liquored should not be cleansed too hot or
a separation will take place, 150° F. (66° C.) may be taken as a
suitable temperature for this class of soap; in the case of firm soaps,
such as milling base, where cooling is liable to take place in the pan
(and thus affect the yield), the temperature may be 165°-170° F.
(74°-77° C.). This latter class of soap is generally run direct to the
frames and crutched by hand, or, to save manual labour, it may be run
into a power-driven crutching pan (neutralising material being added if
necessary) and stirred a few times before framing.

[Illustration: FIG. 3.--Winch.]

[Illustration: FIG. 4.--Soap-boiling pan, showing skimmer pipe, swivel
and winch.]

[Illustration: FIG. 5.--Hand crutch.]

[Illustration: FIG. 6.--Mechanical crutcher.]

_Crutching._--This consists of stirring the hot soap in the frames by
hand crutches (Fig. 5) until the temperature is sufficiently lowered and
the soap begins to assume a "ropiness". Crutching may also be performed
mechanically. There are various types of mechanical crutchers,
stationary and travelling. They may be cylindrical pans, jacketed or
otherwise, in the centre of which is rotated an agitator, consisting of
a vertical or horizontal shaft carrying several blades (Fig. 6) or the
agitator may take the form of an Archimedean screw working in a cylinder
(Fig. 7).

[Illustration: FIG. 7.--Mechanical crutcher.]

The kind of soap to be crutched, whether thin or stiff, will determine
the most suitable type for the purpose. The former class includes
"washer" soap which is generally neutralised, and coloured and perfumed,
if necessary, in these crutching pans, and in that case they are merely
used for mixing the liquids with the hot soap prior to its passage along
wooden spouts (Fig. 8) provided with outlets over the frames, in which
the crutching is continued by hand. In the case of stiff soaps requiring
complete incorporation of liquor, the screw type is preferable, the soap
being forced upwards by the screw, and descending between the cylinder
and the sides of the pan, while the reverse action can also be brought
into play. The completion of crutching is indicated by the smoothness
and stiffness of the soap when moved with a trowel, and a portion taken
out at this point and cooled should present a rounded appearance. When
well mixed the resultant product is emptied directly into wheel-frames
placed underneath the outlet of the pan. It is important that the blades
or worm of the agitating gear be covered with soap to avoid the
occlusion of air and to prevent the soap becoming soft and spongy.

[Illustration: FIG. 8.--Wooden soap spout.]

_Liquoring of Soaps._--This consists of the addition of various alkaline
solutions to soap to produce different qualities, and is best performed
in the crutching machines, although it is in some instances carried out
in the frames. In the history of soap-making a large number and variety
of substances have been suggested for the purpose of accomplishing some
real or supposed desirable effect when added to soap. Many of these have
had only a very short existence, and others have gradually fallen out of
use.

Amongst the more practical additions most frequently adopted may be
mentioned carbonate of soda, silicate of soda, and pearl ash (impure
carbonate of potash). The carbonate of soda may be used in the form of
"soda crystals," which, containing 62.9 per cent. of water, dissolves in
its own water of crystallisation on heating, and is in that manner added
to the hot soap. In the case of weak-bodied soap, this addition gives
firmness and tends to increase the detergent qualities.

The soda carbonate may also be added to soap as a solution of soda ash
(58° alkali) either concentrated, 62° Tw. (34° B.), or of various
strengths from 25° Tw. (16° B.) upwards. This solution stiffens and
hardens soap, and the addition, which must not be excessive, or
efflorescence will occur, is generally made at a temperature of 140° F.
(60° C.). Care should always be taken in the choice of solutions for
liquoring. Strong soda ash solution with a firm soap will result in a
brittle product, whereas the texture of a weak soap would be greatly
improved by such addition.

A slight addition of a weak solution of pearl ash, 4°-8° Tw. (2.7-5.4°
B.), improves the appearance of many soaps intended for household
purposes.

For yellow soaps, containing a low percentage of fatty acids, solutions
of silicate of soda of varying strengths are generally used.

It is always advisable to have a test sample made with the soap to
ascertain what proportion and what strength of sodium silicate solution
is best suited for the grade of soap it is desired to produce. It is
important that the soap to be "silicated" should be distinctly alkaline
(_i.e._, have a distinct caustic taste), or the resultant soap is liable
to become like stone with age. The alkaline silicate of soda (140° Tw.,
59.5° B.) is the quality most convenient for yellow soaps; this may be
diluted to the desired gravity by boiling with water. For a reduction of
3-4 per cent. fatty acids content, a solution of 6° Tw. (4° B.)
(boiling) is most suitable, and if the reduction desired is greater, the
density of the silicate solution should be increased; for example, to
effect a reduction of 20 per cent. fatty acids content, a solution of
18° Tw. (12° B.) (boiling) would probably be found to answer.

In some instances 140° Tw. (59.5° B.) silicate may be added; experiment
alone will demonstrate the amount which can be satisfactorily
incorporated without the soap becoming "open," but 1/10 of the quantity
of soap taken is practically a limit, and it will be found that the
temperature should be low; the same quantity of silicate at different
temperatures does not produce the same result. Various other strengths
of sodium silicate are employed, depending upon the composition and body
of the soap base--neutral silicate 75° Tw. (39.4° B.) also finds favour
with some soap-makers. Mixtures of soda crystals or soda ash solution
with silicate of soda solution are used for a certain grade of soap,
which is crutched until smooth and stiff. Glauber's salt (sodium
sulphate) produces a good smooth surface when added to soap, but, owing
to its tendency to effloresce more quickly than soda carbonate, it is
not so much used as formerly.

Common salt sometimes forms an ingredient in liquoring mixtures.
Potassium chloride and potassium silicate find a limited use for
intermixing with soft soaps.

It will be readily understood that hard and fast rules cannot be laid
down for "liquoring" soap, and the correct solution to be employed can
only be ascertained by experiment and experience, but the above
suggestions will prove useful as a guide towards good results. A smooth,
firm soap of clear, bright, glossy appearance is what should be aimed
at.

_Filling._--Some low-grade soaps contain filling, which serves no useful
purpose beyond the addition of weight. Talc is the most frequently used
article of this description. It consists of hydrated silicate of
magnesium and, when finely ground, is white and greasy to the touch. The
addition of this substance to the hot soap is made by suspending it in
silicate of soda solution.

Whatever filling material is used, it is important that the appearance
of the soap should not be materially altered.

_Neutralising, Colouring and Perfuming._--The free caustic alkali in
soap, intended for toilet or laundry purposes, is usually neutralised
during the cleansing, although some soap manufacturers prefer to
accomplish this during the milling operation. Various materials have
been recommended for the purpose, those in most general use being sodium
bicarbonate, boric acid, cocoa-nut oil, stearic acid, and oleic acid.

The best method is the addition of an exact quantity of sodium
bicarbonate (acid sodium carbonate), which converts the caustic alkali
into carbonate. The reaction may be expressed by the equation:--

          NaOH  +      NaHCO_{3}     =   Na_{2}CO_{3}    + H_{2}O
    Caustic soda  Bicarbonate of soda  Carbonate of soda    Water

Boric acid in aqueous or glycerine solutions, and borax (biborate of
soda) are sometimes used, but care is necessary in employing these
substances, as any excess is liable to decompose the soap.

The addition of cocoa-nut oil is unsatisfactory, the great objection
being that complete saponification is difficult to ensure, and, further,
there is always the liability of rancidity developing. Stearic and oleic
acids are more suitable for the purpose, but oleic acid has the
disadvantage that oleates are very liable to go rancid.

A large number of other substances have been proposed, and in many
instances patented, for neutralising the free caustic alkali. Among
these may be mentioned--Alder Wright's method of using an ammoniacal
salt, the acid radicle of which neutralises the caustic alkali, ammonia
being liberated; the use of sodium and potassium bibasic phosphate (Eng.
Pat. 25,357, 1899); a substance formed by treating albumen with formalin
(Eng. Pat., 8,582, 1900); wheat glutenin "albuminoses" (albumen after
acid or alkaline treatment); malt extract; and egg, milk, or vegetable
albumen.

The colouring matter used may be of either vegetable or coal-tar origin,
and is dissolved in the most suitable medium (lye, water, or fat). The
older types of colouring matter--such as cadmium yellow, ochres,
vermilion, umbers--have been superseded.

In the production of washer household soaps, a small quantity of perfume
is sometimes added.

_Disinfectant Soaps._--To the soap base, which must be strong to taste,
is added from 3 to 4 per cent. of coal-tar derivatives, such as carbolic
acid, cresylic acid, creosote, naphthalene, or compounds containing
carbolic acid and its homologues. The incorporation is made in the
crutching pan, and further crutching may be given by hand in the frames.

_Framing._--The object of framing is to allow the soap to solidify into
blocks. The frames intended for mottled soaps, which require slow
cooling, are constructed of wood, often with a well in the base to allow
excess of lye to accumulate--for other soaps, iron frames are in general
use. The frame manufactured by H. D. Morgan of Liverpool is shown in
Fig. 9.

As soon as the frame is filled, or as soon as the crutching in the frame
is finished, the soap is smoothed by means of a trowel, leaving in the
centre a heap which slopes towards the sides. Next day the top of the
soap is straightened or flattened with a wooden mallet, this treatment
assisting in the consolidation.

[Illustration: FIG. 9.--Soap frame.]

[Illustration: FIG. 10.--Slabbing machine.]

The length of time the soap should remain in frames is dependent on the
quality, quantity, and season or temperature, and varies usually from
three to seven days. When the requisite period has elapsed, the sides
and ends of the frames are removed, and there remains a solid block of
soap weighing from 10 to 15 cwt. according to the size of frame used.
The blocks, after scraping and trimming, are ready for cutting into
slabs.

_Slabbing._--This may be done mechanically by pushing the block of soap
through a framework containing pianoforte wires fixed at equi-distances
(Fig. 10, which shows a machine designed by E. Forshaw & Son, Ltd.), or
the soap may be out by hand by pulling a looped wire through the mass
horizontally along lines previously scribed, or, for a standard sized
slab, the wire may be a fixture in a box-like arrangement, which is
passed along the top of the soap, and the distance of the wire from the
top of the box will be the thickness of the slab (Fig. 11).

[Illustration: FIG. 11.--Banjo slabber.]

All tallow soaps should be slabbed whilst still warm, cut into bars, and
open-piled immediately; if this type of soap is cold when slabbed its
appearance will be very much altered.

_Barring._--The slabs are out transversely into bars by means of the
looped wire, or more usually by a machine (Fig. 12), the lower framework
of which, containing wires, is drawn through the soap placed on the
base-board; the framework is raised, and the bars fall upon the shelf,
ready for transference into piles. It has long been the custom in
England to cut bars of soap 15 inches long, and weighing 3 lb. each, or
37-1/2 bars of soap to the cwt., but in recent years a demand has arisen
for bars of so many various weights that it must be sometimes a
difficult matter to know what sizes to stock.

In another type of barring machine, portions of the slab, previously cut
to size, are pushed against a framework carrying wires, and the bars
slide along a table ready for handling (Fig. 13).

In cutting machines, through which "washer" household soap is being
passed, the bar is pushed at right angles through another frame
containing wires, which divides it into tablets; these may be received
upon racks and are ready for drying and stamping. It is needless to say
that the slabs and tablets are cut with a view to reducing the amount of
waste to the lowest possible limit. Such a machine, made by E. Forshaw &
Son, Ltd., is shown in Fig. 14.

[Illustration: FIG. 12.--Barring machine.]

[Illustration: FIG. 13.--Bar-cutting machine.]

[Illustration: FIG. 14.--Tablet-cutting machine.]

_Open- and Close-piling._--As remarked previously, tallow soaps should
be cut whilst warm, and the bars "open-piled," or stacked across each
other in such a way that air has free access to each bar for a day. The
bar of soap will skin or case-harden, and next day may be "close-piled,"
or placed in the storage bins, where they should remain for two or three
weeks, when they will be in perfect condition for packing into boxes
ready for distribution.

[Illustration: FIG. 15.--Soap stamp.]

_Drying._--"Oil soaps," as soaps of the washer type are termed, do not
skin sufficiently by the open-piling treatment, and are generally
exposed on racks to a current of hot air in a drying chamber in order to
produce the skin, which prevents evaporation of water, and allows of an
impression being given by the stamp without the soap adhering to the
dies. It is of course understood that heavily liquored soaps are, as a
rule, unsuitable for the drying treatment, as the bars become unshapely,
and lose water rapidly.

_Stamping._--Bar soaps are usually stamped by means of a hand-stamp
containing removable or fixed brass letters (Fig. 15), with a certain
brand or designation of quality and the name of the manufacturer or
vendor, and are now ready for packing into boxes.

A very large bulk of the soap trade consists of the household quality in
tablet form, readily divided into two cakes. These are stamped in the
ordinary box moulds with two dies--top and bottom impressions--the
die-plates, being removable, allow the impressions to be changed. This
type of mould (Fig. 16) can be adjusted for the compression of tablets
of varying thickness, the box preventing the escape of soap. We are
indebted to E. Forshaw & Son, Ltd., for this illustration.

[Illustration: FIG. 16.--Box mould.]

The stamping machine may be worked by hand (Fig. 17) or power driven.
Where large quantities of a particular tablet have to be stamped, one of
the many automatic mechanical stampers in existence may be employed, the
tablets being conveyed to and from the dies by means of endless belts.
Such a machine is shown in the accompanying illustration (Fig. 18).

If necessary, the soap is transferred to racks and exposed to the air,
after which it is ready for wrapping, which is generally performed by
manual labour, although in some instances automatic wrapping machines
are in use.

Cardboard cartons are also used for encasing the wrapped tablets, the
object being that these are more conveniently handled by tradesmen and
may be advantageously used to form an attractive window display.

_Cooling._--Many attempts have been made to shorten the time required
for the framing and finishing of soap, by cooling the liquid soap as it
leaves the pan.

[Illustration: FIG. 17.--Soap-stamping machine, showing box mould.]

With milling base, this is successfully accomplished in the
Cressonnières' plant, by allowing the hot soap to fall upon the
periphery of a revolving drum which can be cooled internally by means of
water.

[Illustration: FIG. 18.--Automatic stamper.]

In the case of household soaps, where the resultant product must be of
good appearance and have a firm texture, the difficulty is to produce a
bar fit for sale after the cooling has been performed, as soap which has
been suddenly chilled lacks the appearance of that treated in the
ordinary way. Several patents have been granted for various methods of
moulding into bars in tubes, where the hot soap is cooled by being
either surrounded by running water in a machine of similar construction
to a candle machine, or rotated through a cooling medium; and numerous
claims have been made both for mechanical appliances and for methods of
removing or discharging the bars after cooling. In many instances these
have proved unsatisfactory, owing to fracture of the crystalline
structure. Moreover, in passing through some of the devices for
solidification after chilling, the soap is churned by means of a worm or
screw, and this interferes with the firmness of the finished bar, for,
as is well known, soap which has been handled too much, does not regain
its former firmness, and its appearance is rendered unsatisfactory.

A form of apparatus which is now giving satisfactory results is the
Leimdoerfer continuous cooler (Fig. 19). This consists of a fixed
charging hopper, A, a portable tank, B, containing tubes, and a
detachable box, C, which can be raised or lowered by means of a screw,
D. The bottom of the hopper is fitted with holes corresponding with the
cooling tubes, _e_, and closed by plugs _c_, attached to a frame _b_,
which terminates above in a screw spindle _a_, by means of which the
frame and plugs can be raised and lowered so as to permit or stop the
outflow of soap into the cooling tubes. The tubes are closed at the
bottom by slides _d_, and the box B, in which they are mounted, is
carried on a truck running on rails. The charging hopper can be
connected with the soap-pan by a pipe, and when the hopper is filled
with liquid soap the plugs _c_ are raised and the air in the box C
exhausted, thus causing the soap to descend into the cooling tubes.

[Illustration: FIG. 19.--Leimdoerfer cooler.]

The slides _d_ are closed, the screw D released, and the box B moved
away to make room for another. At the end of the rail track is an
ejecting device which pushes the cooled soap out of the tubes, and the
truck is run back on a side track to the machine for use over again. In
this way the apparatus can be worked continuously, the soap being
received from the cooling pipes on a suitable arrangement for transport
to the press or store room.

A similar idea has been made the subject of a patent by Holoubek (Eng.
Pat. 24,440, 1904, Fig. 20). The soap is run into frames or moulds
having open sides, which are closed by being clamped with screws and
pressure plates between cooling tubes through which water circulates.

[Illustration: FIG. 20.--Holoubek's cooler.]



CHAPTER VII.

TOILET, TEXTILE AND MISCELLANEOUS SOAPS.

     _Toilet Soaps--Cold Process Soaps--Settled Boiled
     Soaps--Remelted Soaps--Milled Soaps--Drying--Milling and
     Incorporating Colour, Perfume, or
     Medicament--Perfume--Colouring Matter--Neutralising and
     Superfatting
     Material--Compressing--Cutting--Stamping--Medicated
     Soaps--Ether Soap--Floating Soaps--Shaving Soaps--Textile
     Soaps--Soaps for Woollen, Cotton and Silk Industries--Patent
     Textile Soaps--Miscellaneous Soaps._


_Toilet Soaps._--By the term "toilet soap" is inferred a soap specially
adapted for toilet use by reason not only of its good detergent and
lathering qualities, but also on account of its freedom from caustic
alkali and any other ingredient likely to cause irritation or injury to
the skin.

Toilet soaps may be simply classified according to their method of
preparation into the following four classes:--

          (1) Cold process soaps.
          (2) Settled boiled soaps.
          (3) Remelted soaps.
          (4) Milled soaps.

Soaps of the first class are of comparatively trifling importance,
having been superseded by the other qualities. Details of the "cold
process" have already been given on page 46; it is only necessary to add
the desired perfume and colouring matter to the soap.

The second class consists of good quality settled soaps, direct from the
copper, to which have been added, prior to framing, suitable perfume and
colouring matter, also, if necessary, dealkalising materials.

The third class is represented by soaps made by the old English method
of remelting, which are often termed "perfumers'," or "little pan"
soaps. The soap-base or mixture of various kinds of soap is remelted in
a steam-jacketed pan, or pan provided with steam coils, and agitated.
The agitation must not be too vigorous or lengthy, or the soap will
become aerated. When all the soap is molten, additions of pearl ash
solution are made to give it a finer and smoother texture, render it
more transparent, and increase its lathering properties. The necessary
colour, in a soluble form, is well incorporated, and lastly the perfume.
Owing to volatilisation, much of the perfume is lost when added to hot
soap, and it is necessary to add a large quantity to get the desired
odour; hence the cheaper essential oils have to be used, so that the
perfume of this class of soap is not so delicate as that of milled
soaps, although it is quite possible to produce remelted soaps as free
from uncombined alkali as a milled toilet soap.

Palm-oil soap often forms the basis for yellow and brown toilet soaps of
this class. The old-fashioned Brown Windsor soap was originally a curd
soap that with age and frequent remelting had acquired a brown tint by
oxidation of the fatty acids--the oftener remelted the better the
resultant soap.

Medicaments are sometimes added to these soaps, _e.g._, camphor, borax,
coal-tar, or carbolic. Oatmeal and bran have been recommended in
combination with soap for toilet purposes, and a patent (Eng. Pat.
26,396, 1896) has been granted for the use of these substances together
with wood-fibre impregnated with boric acid.

After cooling in small frames, the soap is slabbed, and cut into blocks,
and finally into portions suitable for stamping in a press (hand or
steam driven) with a design or lettering on each side.

_Milled Toilet Soaps._--Practically all high-class soaps now on the
market pass through the French or milling process. This treatment, as
its name implies, was first practised by the French who introduced it to
this country, and consists briefly of (i.) drying, (ii.) milling and
incorporating colour, perfume or medicament, (iii.) compressing, and
(iv.) cutting and stamping.

The advantages of milled soap over toilet soap produced by other methods
are that the former, containing less water and more actual soap, is more
economical in use, possesses a better appearance, and more elegant
finish, does not shrink or lose its shape, is more uniform in
composition, and essential oils and delicate perfumes may be
incorporated without fear of loss or deterioration.

Only soap made from best quality fats is usually milled, a suitable base
being that obtained by saponifying a blend of the finest white tallow
with a proportion, not exceeding 25 per cent., of cocoa-nut oil, and
prepared as described in Chapter V.

The first essential of a milling base is that the saponification should
be thorough and complete; if this is not ensured, rancidity is liable to
occur and a satisfactory toilet soap cannot be produced. The soap must
not be short in texture or brittle and liable to split, but of a firm
and somewhat plastic consistency.

(i.) _Drying._--The milling-base, after solidification in the frames,
contains almost invariably from 28 to 30 per cent. of water, and this
quantity must be reduced to rather less than half before the soap can be
satisfactorily milled. Cutting the soap into bars or strips and open
piling greatly facilitates the drying, which is usually effected by
chipping the soap and exposing it on trays to a current of hot air at
95-105° F. (35-40° C.).

There are several forms of drying chambers in which the trays of chips
are placed upon a series of racks one above another, and warm air
circulated through, and Fig. 21 shows a soap drying apparatus with fan
made by W. J. Fraser & Co., Ltd., London.

The older method of heating the air by allowing it to pass over a pipe
or flue through which the products of combustion from a coke or coal
fire are proceeding under the floor of the drying chamber to a small
shaft, has been superseded by steam heat. The air is either drawn or
forced by means of quickly revolving fans through a cylinder placed in a
horizontal position and containing steam coils, or passed over
steam-pipes laid under the iron grating forming the floor of the
chamber.

[Illustration: FIG. 21.--Soap-drying apparatus.]

It will be readily understood that in the case of a bad conductor of
heat, like soap-chippings, it is difficult to evaporate moisture
without constantly moving them and exposing fresh surfaces to the
action of heat.

In the Cressonnières' system, where the shavings of chilled soap are
dried by being carried through a heated chamber upon a series of endless
bands (the first discharging the contents on to a lower belt which
projects at the end, and is moving in the opposite direction, and so
on), this is performed by intercepting milling rollers in the system of
belts (Eng. Pat. 4,916, 1898) whereby the surfaces exposed to the drying
are altered, and it is claimed that the formation of hardened crust is
prevented.

In the ordinary methods of drying, the chips are frequently moved by
hand to assist uniform evaporation.

The degree of saturation of the air with moisture must be taken into
consideration in regulating the temperature and flow of air through the
drying chamber, and for this purpose the use of a hygrometer is
advantageous.

It is very important that the correct amount of moisture should be left
in the soap, not too much, nor too little; the exact point can only be
determined by judgment and experience, and depends to a considerable
extent upon the nature of the soap, and also on the amount of perfume or
medicament to be added, but speaking generally, a range of 11 to 14 per
cent. gives good results. If the soap contains less than this amount it
is liable to crumble during the milling, will not compress
satisfactorily, and the finished tablet may have a tendency to crack and
contain gritty particles so objectionable in use. If, on the other hand,
the soap is left too moist, it is apt to stick to the rollers and mill
with difficulty, and during compression the surface assumes a blistered
and sticky appearance.

(ii.) _Milling and Incorporation of Colour, Perfume or Medicament._--The
object of milling is to render the soap perfectly homogeneous, and to
reduce it to a state in which colour, perfume, or any necessary
neutralising material or other substance may be thoroughly incorporated.
The milling machine consists of smooth granite rollers, fitted with
suitable gearing and working in an iron framework (Fig. 22). The rollers
are connected in such a manner that they rotate at different speeds, and
this increases the efficiency of the milling, and ensures that the
action of the rollers is one of rubbing rather than crushing.

By means of suitably arranged screws the pressure of the rollers on one
another can be adjusted to give the issuing soap any desired thickness;
care should be taken that the sheets of soap are not unnecessarily thick
or the colour and odour will not be uniform.

The soap, in the form of chips, is introduced on to the rollers through
a hopper, and after one passage through the mill, from bottom to top,
one of the serrated knife edges is applied and the ribbons of the soap
are delivered into the top of the hopper where the colour, perfume, and
any other desired admixture is added, and the milling operation repeated
three or four times. When the incorporation is complete the other
scraper is fixed against the top roller and the soap ribbon passed into
the receptacle from which it is conveyed to the compressor. A better
plan, however, especially in the case of the best grade soaps, where the
perfumes added are necessarily more delicate and costly, is to make the
addition of the perfume when the colour has been thoroughly mixed
throughout the mass. Another method is to mill once and transfer the
mass to a rotary mixing machine, fitted with internal blades, of a
peculiar form, which revolve in opposite directions one within the other
as the mixer is rotated. The perfume, colouring matter, etc., are added
and the mixer closed and set in motion, when, after a short time, the
soap is reduced to a fine granular condition, with the colour and
perfume evenly distributed throughout the whole. By the use of such
machines, the loss of perfume by evaporation, which during milling is
quite appreciable, is reduced to a minimum, and the delicacy of the
aroma is preserved unimpaired.

[Illustration: FIG. 22.--Milling machine.]

Prolonged milling, especially with a suitable soap base, tends to
produce a semi-transparent appearance, which is admired by some, but the
increased cost of production by the repeated milling is not accompanied
by any real improvement in the soap.

_Perfume._--The materials used in perfuming soap will be dealt with
fully in the next chapter. The quantity necessary to be added varies
considerably with the nature of the essential oils, and also the price
at which the soap is intended to be sold. In the cheaper grades of
milled soaps the quantity will range from 10-30 fluid ozs. per cwt., and
but rarely exceeds 18-20 ozs., whereas in more costly soaps as much as
40-50 fluid ozs. are sometimes added to the cwt.

_Colouring Matter._--During recent years an outcry has been made against
highly coloured soaps, and the highest class soaps have been
manufactured either colourless or at the most with only a very delicate
tint. It is obvious that a white soap guarantees the use of only the
highest grade oils and fats, and excludes the introduction of any rosin,
and, so far, the desire for a white soap is doubtless justified. Many
perfumes, however, tend to quickly discolour a soap, hence the advantage
of giving it a slight tint. For this purpose a vegetable colouring
matter is preferable, and chlorophyll is very suitable.

[Illustration: FIG. 23.--Compressor.]

A demand still exists for brightly coloured soaps, and this is usually
met by the use of coal-tar dyes. The quantity required is of course
extremely small, so that no harm or disagreeable result could possibly
arise from their use.

_Neutralising and Superfatting Material._--If desired, the final
neutralisation of free alkali can be carried out during the milling
process, any superfatting material being added at the same time. The
chief neutralising reagents have already been mentioned in Chapter VI.

With regard to superfatting material, the quantity of this should be
very small, not exceeding 6-8 ozs. per cwt: The most suitable materials
are vaseline, lanoline, or spermaceti.

[Illustration: FIG. 24--Hand soap-stamping press.]

(iii.) _Compressing._--The next stage is the compression and binding of
the soap ribbons into a solid bar suitable for stamping, and the plant
used (Fig. 23) for this purpose is substantially the same in all
factories. The soap is fed through a hopper into a strong metal
conical-shaped tube like a cannon, which tapers towards the nozzle, and
in which a single or twin screw is moving, and the soap is thereby
forced through a perforated metallic disc, subjected to great pressure,
and compressed. The screws must be kept uniformly covered with shavings
during compression to obviate air bubbles in the soap.

[Illustration: FIG. 25.--Screw press.]

The soap finally emerges through the nozzle (to which is attached a
cutter of suitable shape and size according to the form it is intended
the final tablet to take) as a long, polished, solid bar, which is cut
with a knife or wire into lengths of 2 or 3 feet, and if of satisfactory
appearance, is ready for cutting and stamping. The nozzle of the plodder
is heated by means of a Bunsen burner to about 120° or 130° F. (49°-55°
C.) to allow the soap to be easily forced out, and this also imparts a
good gloss and finish to the ejected bar--if the nozzle is too hot,
however, the soap will be blistered, whereas insufficient heat will
result in streaky soap of a poor and dull appearance.

(iv.) _Cutting and Stamping._--In cutting the soap into sections for
stamping, the cutter should shape it somewhat similar to the required
finished tablet.

Many manufacturers cut the soap into sections having concave ends, and
in stamping, the corners are forced into the concavity, with the result
that unsightly markings are produced at each end of the tablet. It is
preferable to have a cutter with convex ends, and if the stamping is to
be done in a pin mould the shape should be a trifle larger than the
exact size of the desired tablet.

[Illustration: FIG. 26--Pin mould.]

The stamping may be performed by a hand stamper (Fig. 24), a screw press
(Fig. 25), or by a steam stamper. The screw press works very
satisfactorily for toilet soaps.

There are two kinds of moulds in use for milled soaps:--

(_a_) _Pin Moulds_ in which tablets of one size and shape only can be
produced (Fig. 25). The edges of the mould meet very exactly, the upper
part of the die carries two pins attached to the shoulder, and these are
received into two holes in the shoulder of the bottom plate. The
superfluous soap is forced out as the dies meet.

(_b_) _Band or Collar Moulds._--In this form (Fig, 27) the mould may be
adjusted to stamp various sized tablets, say from 2 ozs. to 5-1/3 ozs.
and different impressions given by means of removable die plates. The
band or collar prevents the soap squeezing out sideways. We are indebted
to R. Forehaw & Son, Ltd., for the loan of this illustration.

It is usual to moisten the soap or mould with a dilute solution of
glycerine if it should have a tendency to stick to the die plates.

The soap is then ready for final trimming, wrapping, and boxing.

[Illustration: FIG. 27--Band Mould.]


MEDICATED SOAPS.

The inherent cleansing power of soap renders it invaluable in combating
disease, while it also has distinct germicidal properties, a 2 per cent.
solution proving fatal to B. coli communis in less than six hours, and
even a 1 per cent. solution having a marked action on germs in fifteen
minutes.

Many makers, however, seek more or less successfully to still further
increase the value of soap in this direction by the incorporation of
various drugs and chemicals; and the number of medicated soaps on the
market is now very large. Such soaps may consist of either hard or soft
soaps to which certain medicaments have been added, and can be roughly
divided into two classes, (_a_) those which contain a specific for
various definite diseases, the intention being that the remedy should be
absorbed by the pores of the skin and thus penetrate the system, and
(_b_) those impregnated with chemicals intended to act as antiseptics or
germicides, or, generally, as disinfectants.

The preparation of medicinal soaps appears to have been first taken up
in a scientific manner by Unna of Hamburg in 1886, who advocated the use
of soap in preference to plasters as a vehicle for the application of
certain remedies.

Theoretically, he considered a soap-stock made entirely from beef tallow
the most suitable for the purpose, but in practice found that the best
results were obtained by using a superfatted soap made from a blend of
one part of olive oil with eight parts of beef tallow, saponified with a
mixture of two parts of soda to one part of potash, sufficient fat being
employed to leave an excess of 3 or 4 per cent. unsaponified. Recent
researches have shown, however, that even if a superfatted soap-base is
beneficial for the preparation of toilet soaps (a point which is open to
doubt), it is quite inadmissible for the manufacture of germicidal and
disinfectant soaps, the bactericidal efficiency of which is much
restricted by the presence of free fat.

Many of the medicaments added to soaps require special methods of
incorporation therein, as they otherwise react with the soap and
decompose it, forming comparatively inert compounds. This applies
particularly to salts of mercury, such as _corrosive sublimate_ or
mercuric chloride, and _biniodide of mercury_, both of which have very
considerable germicidal power, and are consequently frequently added to
soaps. If simply mixed with the soap in the mill, reaction very quickly
takes place between the mercury salt and the soap, with formation of the
insoluble mercury compounds of the fatty acids, a change which can be
readily seen to occur in such a soap by the rapid development on
keeping, of a dull slaty-green appearance. Numerous processes have been
suggested, and in some cases patented, to overcome this difficulty. In
the case of corrosive sublimate, Geissler suggested that the soap to
which this reagent is to be added should contain an excess of fatty
acids, and would thereby be rendered stable. This salt has also been
incorporated with milled soap in a dry state in conjunction with
ammonio-mercuric chloride, [beta]-naphthol, methyl salicylate, and
eucalyptol. It is claimed that these bodies are present in an unchanged
condition, and become active when the soap is added to water as in
washing. Ehrhardt (Eng. Pat. 2,407, 1898) patented a method of making
antiseptic mercury soap by using mercury albuminate--a combination of
mercuric chloride and casein, which is soluble in alkali, and added to
the soap in an alkaline solution.

With biniodide of mercury the interaction can be readily obviated by
adding to the biniodide of mercury an equal weight of potassium iodide.
This process, devised and patented by J. Thomson in 1886, has been
worked since that time with extremely satisfactory results. Strengths of
1/2, 1, and 3 per cent. biniodide are sold, but owing to the readiness
with which it is absorbed by the skin a soap containing more than 1/2
per cent. should only be used under medical advice.

A similar combination of _bromide of mercury_ with potassium, sodium, or
ammonium bromide has recently been patented by Cooke for admixture with
liquid, hard, or soft soaps.

_Zinc and other Metallic Salts._--At various times salts of metals other
than mercury have been added to soap, but, owing to their insolubility
in water, their efficiency as medicaments is very trifling or nil.
Compounds have been formed of metallic oxides and other salts with oleic
said, and mixtures made with vaseline and lanoline, and incorporated
with soap, but they have not met with much success.

Another chemical commonly added to soap is _Borax_. In view of its
alkaline reaction to litmus, turning red litmus blue, this salt is no
doubt generally regarded as alkaline, and, as such, without action on
soap. On the contrary, however, it is an acid salt containing an excess
of boric acid over the soda present, hence when it is added to soap,
fatty acids are necessarily liberated, causing the soap to quickly
become rancid. As a remedy for this it has been proposed to add
sufficient alkali to convert the borax into neutral mono-borate of soda
which is then added to the soap. This process is patented and the name
"Kastilis" has been given to the neutral salt. The incorporation of
borax with the addition of gum tragasol forms the subject of two patents
(Eng. Pats. 4,415, 1904; and 25,425, 1905); increased detergent and
lasting properties are claimed for the soap. Another patented process
(Eng. Pat. 17,218, 1904) consists of coating the borax with a protective
layer of fat or wax before adding to the soap with the idea that
reaction will not take place until required. _Boric acid_ possesses the
defects of borax in a greater degree, and would, of course, simply form
sodium borate with liberation of fatty acids, so should never be added
to a neutral soap.

_Salicylic Acid_ is often recommended for certain skin diseases, and
here again the addition of the acid to soap under ordinary conditions
results in the formation of sodium salicylate and free fatty acids.

To overcome this a process has recently been patented for rubbing the
acid up with vaseline before addition to soap, but the simplest way
appears to be to add the soda salt of the acid to soap.

Amongst the more common milled medicated toilet soaps may be mentioned,
in addition to the above:--

_Birch Tar Soap_, containing 5 or 10 per cent. birch tar, which has a
characteristic pungent odour and is recommended as a remedy for eczema
and psoriasis.

_Carbolic Soap._--A toilet soap should not contain more than 3 per cent.
of pure phenol, for with larger quantities irritation is likely to be
experienced by susceptible skins.

_Coal Tar._--These soaps contain, in addition to carbolic acid and its
homologues, naphthalene and other hydrocarbons derived from coal,
naphthol, bases, etc. Various blends of different fractions of coal tar
are used, but the most valuable constituents from a disinfectant point
of view are undoubtedly the phenols, or tar acids, though in this case
as with carbolic and cresylic soaps, the amount of phenols should not
exceed 3 per cent. in a toilet soap. An excess of naphthalene should
also be avoided, since, on account of its strong odour, soaps containing
much of it are unpopular. The odour of coal tar is considerably modified
by and blends well with a perfume containing oils of cassia, lavender,
spike, and red thyme.

_Formaldehyde._--This substance is one of the most powerful
disinfectants known, and it may be readily introduced into soap without
undergoing any decomposition, by milling in 2-3 per cent. of formalin, a
40 per cent. aqueous solution of formaldehyde, which is a gas. White
soaps containing this chemical retain their whiteness almost
indefinitely.

New combinations of formaldehyde with other bodies are constantly being
brought forward as disinfectants. Among others the compound resulting
from heating lanoline with formaldehyde has been patented (Eng. Pat.
7,169, 1898), and is recommended as an antiseptic medicament for
incorporation with soap.

_Glycerine._--Nearly all soaps contain a small quantity of this body
which is not separated in the lyes. In some cases, however, a much
larger quantity is desired, up to some 6 or 8 per cent. To mill this in
requires great care, otherwise the soap tends to blister during
compression. The best way is to dry the soap somewhat further than
usual, till it contains say only 9 or 10 per cent. moisture and then
mill in the glycerine.

_Ichthyol_ or _Ammonium-Ichthyol-Sulphonate_ is prepared by treating
with sulphuric acid, and afterwards with ammonia, the hydrocarbon oil
containing sulphur obtained by the dry distillation of the fossil
remains of fish and sea-animals, which form a bituminous mineral deposit
in Germany. This product has been admixed with soap for many years, the
quantity generally used being about 5 per cent.; the resultant soap is
possessed of a characteristic empyreumatic smell, very dark colour, and
is recommended for rosacea and various skin diseases, and also as an
anti-rheumatic. Ichthyol has somewhat changed its character during
recent years, being now almost completely soluble in water, and stronger
in odour than formerly.

_Iodine._--A soap containing iodine is sometimes used in scrofulous skin
diseases. It should contain some 3 per cent. iodine, while potassium
iodide should also be added to render the iodine soluble.

_Lysol._--This name is applied to a soap solution of cresol, "Lysol
Soap" being simply another form of coal-tar soap. The usual strength is
10 per cent. lysol, and constitutes a patented article (Fr. Pat.
359,061, 1905).

_Naphthol._--[beta]-Naphthol, also a coal-tar derivative, is a good
germicide, and, incorporated in soap to the extent of 3 per cent.
together with sulphur, is recommended for scabies, eczema and many other
cutaneous affections.

_Sulphur._--Since sulphur is insoluble in water, its action when used in
conjunction with soap can be but very slow and slight. Sulphur soaps
are, however, very commonly sold, and 10 per cent. is the strength
usually advocated, though many so-called sulphur soaps actually contain
very little sulphur. They are said to be efficacious for acne and
rosacea.

Sulphur soaps, when dissolved in water, gradually generate sulphuretted
hydrogen, which, although characteristic, makes their use disagreeable
and lessens their popular estimation.

_Terebene._--The addition of this substance to soap, though imparting a
very refreshing and pleasant odour, does not materially increase the
disinfectant value of the soap. A suitable strength is 5 per cent.

_Thymol._--This furnishes a not unpleasant, and very useful antiseptic
soap, recommended especially for the cleansing of ulcerated wounds and
restoring the skin to a healthy state. The normal strength is 3 per
cent. It is preferable to replace part of the thymol with red thyme oil,
the thymene of which imparts a sweeter odour to the soap than if
produced with thymol alone. A suitable blend is 2-1/2 per cent. of
thymol crystals and 1-1/2 per cent. of a good red thyme oil.

Of the vast number of less known proposed additions to toilet soaps,
mention may be made in passing of:--

_Fluorides._--These have been somewhat popular during recent years for
the disinfection of breweries, etc., and also used to some extent as
food preservatives. Of course only neutral fluorides are available for
use in soap, acid fluorides and soap being obviously incompatible. In
the authors' experience, however, sodium fluoride appears to have little
value as a germicide when added to soap, such soaps being found to
rapidly become rancid and change colour.

_Albumen._--The use of albumen--egg, milk, and vegetable--in soap has
been persistently advocated in this country during the past few years.
The claims attributed to albumen are, that it neutralises free alkali,
causes the soap to yield a more copious lather, and helps to bind it
more closely, and a further inducement held out is that it allows more
water to be left in the soap without affecting its firmness. Experiments
made by the authors did not appear to justify any enthusiasm on the
subject, and the use of albumen for soap-making in this country appears
to be very slight, however popular it may be on the Continent. Numerous
other substances have been proposed for addition to soaps, including
yeast, tar from peat (sphagnol), Swedish wood tar, permanganate of
potash, perborates and percarbonates of soda and ammonia, chlorine
compounds, but none of these has at present come much into favour, and
some had only ephemeral existence. Of the many drugs that it has been
suggested to admix in soap for use in allaying an irritable condition of
the skin, the majority are obviously better applied in the form of
ointments, and we need not consider them further.

_Ether Soap._--Another form of medicated soap made by a few firms is a
liquid ether soap containing mercuric iodide, and intended for surgeons'
use. This, as a rule, consists of a soap made from olive oil and potash,
dissolved in alcohol and mixed with ether, the mercuric iodide being
dissolved in a few drops of water containing an equal weight of
potassium iodide, and this solution added to the alcohol-ether soap.

_Floating Soaps._--Attempts have been made to produce tablets of soap
that will float upon the surface of water, by inserting cork, or floats,
or a metallic plate in such a manner that there is an air space between
the metal and the soap. The more usual method is to incorporate into
hot soap sufficient air, by means of a specially designed self-contained
jacketed crutcher, in which two shafts carrying small blades or paddles
rotate in opposite directions, to reduce the density of the soap below
that of water and so enable the compressed tablet to float. The
difference in weight of a tablet of the same size before and after
aerating amounts to 10 per cent.

Ordinary milling soap is used as a basis for this soap; the settled soap
direct from the copper at 170° F. (77° C.) is carefully neutralised with
bicarbonate of sodium, oleic or stearic acids, or boro-glyceride,
perfumed and aerated.

Floating soap, which is usually white (some are of a cream tint), cannot
be recommended as economical, whilst its deficiency in lathering
properties, owing to occluded air, is a serious drawback to its
popularity as a toilet detergent.

_Shaving Soaps._--The first essential of a shaving soap, apart from its
freedom from caustic alkali or any substance exerting an irritating
effect upon the skin, is the quick production of a profuse creamy lather
which is lasting. Gum tragacanth is used in some cases to give lasting
power or durability, but is not necessary, as this property is readily
attained by the use of a suitable proportion of potash soap. The best
shaving soaps are mixtures of various proportions of neutral soda and
potash soaps, produced by the combination of ordinary milling base with
a white potash soap, either melted or milled together. Glycerine is
sometimes added, and is more satisfactorily milled in.

Every precaution should be taken to ensure thorough saponification of
the soaps intended for blending in shaving soap, otherwise there will be
a tendency to become discoloured and develop rancidity with age. Shaving
soaps are delicately perfumed, and are placed on the market either in
the form of sticks which are cut from the bar of soap as it leaves the
compressor, or stamped in flat cakes.

Shaving creams and pastes are of the same nature as shaving soaps, but
usually contain a larger proportion of superfatting material and
considerably more water.


TEXTILE SOAPS.

In the woollen, cloth, and silk textile industries, the use of soap for
detergent and emulsifying purposes is necessary in several of the
processes, and the following is a brief description of the kinds of soap
successfully employed in the various stages.

1. _Woollen Industry._--The scouring of wool is the most important
operation--it is the first treatment raw wool is subjected to, and if it
is not performed in an efficient manner, gives rise to serious
subsequent troubles to manufacturer, dyer, and finisher.

The object of scouring wool is to remove the wool-fat and wool
perspiration (exuded from the skin of sheep), consisting of cholesterol
and isocholesterol, and potassium salts of fatty acids, together with
other salts, such as sulphates, chlorides, and phosphates. This is
effected by washing in a warm dilute soap solution, containing in the
case of low quality wool, a little carbonate of soda; the fatty matter
is thereby emulsified and easily removed.

Soap, to be suitable for the purpose, must be free from uncombined
caustic alkali, unsaponified fat, silicates, and rosin.

Wool can be dissolved in a moderately dilute solution of caustic soda,
and the presence of this latter in soap, even in small quantities, is
therefore liable to injure the fibres and make the resultant fabric
possess a harsh "feel," and be devoid of lustre.

Unsaponified fat denotes badly made soap--besides reducing the
emulsifying power of the liberated alkali, this fat may be absorbed by
the fibres and not only induce rancidity but also cause trouble in
dyeing.

Soaps containing silicates may have a deleterious action upon the
fibres, causing them to become damaged and broken.

By general consent soaps containing rosin are unsuitable for use by
woollen manufacturers, as they produce sticky insoluble lime and
magnesia compounds which are deposited upon the fibres, and give rise to
unevenness in the dyeing.

A neutral olive-oil soft soap is undoubtedly the best for the purpose of
wool scouring, as, owing to its ready solubility in water, it quickly
penetrates the fibres, is easily washed out, and produces a good "feel"
so essential in the best goods, and tends to preserve the lustre and
pliability of the fibre.

The high price of olive-oil soap, however, renders its use prohibitive
for lower class goods, and in such cases no better soap can be suggested
than the old-fashioned curd mottled or curd soaps (boiled very dry), as
free as possible from uncombined caustic alkali. The raw wool, after
this cleansing operation, is oiled with olive oil or oleine, prior to
spinning; after spinning and weaving, the fabric, in the form of yarn or
cloth, has to be scoured to free it from oil. The soap in most general
use for scouring woollen fabrics is neutral oleine-soda soap. Some
manufacturers prefer a cheap curd soap, such as is generally termed
"second curd," and in cases where lower grades of wools are handled, the
user is often willing to have soap containing rosin (owing to its
cheapness) and considers a little alkalinity desirable to assist in
removing the oil.

Another operation in which soap is used, is that of milling or fulling,
whereby the fabric is made to shrink and thus becomes more compact and
closer in texture. The fabric is thoroughly cleansed, for which purpose
the soap should be neutral and free from rosin and silicates, otherwise
a harsh feeling or stickiness will be produced. Curd soaps or
finely-fitted soaps made from tallow or bleached palm oil, with or
without the addition of cocoa-nut oil, give the best results. All traces
of soap must be carefully removed if the fabric is to be dyed.

The woollen dyer uses soap on the dyed pieces to assist the milling,
and finds that a good soap, made from either olive oil, bleached palm
oil, or tallow, is preferable, and, although it is generally specified
to be free from alkali, a little alkalinity is not of consequence, for
the woollen goods are, as a rule, acid after dyeing, and this alkalinity
would be instantly neutralised.

2. _Cotton Industry._--Cotton fibres are unacted upon by caustic alkali,
so that the soap used in cleaning and preparing cotton goods for dyeing
need not be neutral, in fact alkalinity is a distinct advantage in order
to assist the cleansing.

Any curd soap made from tallow, with or without the addition of a small
quantity of cocoa-nut oil, may be advantageously used for removing the
natural oil.

In cotton dyeing, additions of soap are often made to the bath, and in
such cases the soap must be of good odour and neutral, lest the colours
should be acted upon and tints altered. Soaps made from olive oil and
palm oil are recommended. The same kind of soap is sometimes used for
soaping the dyed cotton goods.

The calico-printer uses considerable quantities of soap for cleansing
the printed-cloths. The soap not only cleanses by helping to remove the
gummy and starchy constituents of the adhering printing paste, but also
plays an important part in fixing and brightening the colours. Soaps
intended for this class of work must be quite neutral (to obviate any
possible alteration in colour by the action of free alkali), free from
objectionable odour and rosin, and readily soluble in water. These
qualities are possessed by olive-oil soaps, either soft or hard. A
neutral olive-oil soft soap, owing to its solubility in cold water, may
be used for fibres coloured with most delicate dyes, which would be
fugitive in hot soap solutions, and this soap is employed for the most
expensive work.

Olive-oil curd (soda) soaps are in general use; those made from palm oil
are also recommended, although they are not so soluble as the olive-oil
soaps. Tallow curd soaps are sometimes used, but the difficulty with
which they dissolve is a drawback, and renders them somewhat unsuitable.

3. _Silk Industry._--Silk is secured to remove the sericin or silk-glue
and adhering matter from the raw silk, producing thereby lustre on the
softened fibre and thus preparing it for the dyer.

The very best soap for the purpose is an olive-oil soft soap; olive-oil
and oleine hard soaps may also be used. The soap is often used in
conjunction with carbonate of soda to assist the removal of the sericin,
but, whilst carbonates are permissible, it is necessary to avoid an
excess of caustic soda.

Tallow soaps are so slowly soluble that they are not applicable to the
scouring of silk.

The dyer of silk requires soap, which is neutral and of a pleasant
odour. The preference is given to neutral olive-oil soft soap, but hard
soaps (made from olive oil, oleine, or palm oil) are used chiefly on
account of cheapness. It is essential, however, that the soap should be
free from rosin on account of its frequent use and consequent
decomposition in the acid dye bath, when any liberated rosin acids would
cling to the silk fibres and produce disagreeable results.

_Patent Textile Soaps._--Stockhausen (Eng. Pat. 24,868, 1897) makes
special claim for a soap, termed Monopole Soap, to be used in place of
Turkey-red oils in the dyeing and printing of cotton goods and finishing
of textile fabrics. The soap is prepared by heating the sulphonated oil
(obtained on treatment of castor oil with sulphuric acid) with alkali,
and it is stated that the product is not precipitated when used in the
dye-bath as is ordinary soap, nor is it deposited upon the fibres.

Another patent (Eng. Pat. 16,382, 1897), has for its object the
obviating of the injurious effects upon wool, of alkali liberated from a
solution of soap. It is proposed to accomplish this by sulphonating part
of the fat used in making the soap.

_Miscellaneous Soaps._--Under this heading may be classed soaps intended
for special purposes and consisting essentially of ordinary boiled soap
to which additions of various substances have been made.

With additions of naphtha, fractions of petroleum, and turpentine, the
detergent power of the soap is increased by the action of these
substances in removing grease.

Amongst the many other additions may be mentioned: ox-gall or
derivatives therefrom (for carpet-cleaning soap), alkali sulphides (for
use of lead-workers), aniline colours (for home-dyeing soaps), pumice
and tripoli (motorists' soaps), pine-needle oil, in some instances
together with lanoline (for massage soaps), pearl-ash (for soap intended
to remove oil and tar stains), magnesia, rouge, ammonium carbonate,
chalk (silversmiths' soap), powdered orris, precipitated chalk,
magnesium carbonate (tooth soaps).

Soap powders or dry soaps are powdered mixtures of soap, soda ash, or
soda crystals, and other chemicals, whilst polishing soaps often contain
from 85 to 90 per cent. siliceous matter, and can scarcely be termed
soap.



CHAPTER VIII.

SOAP PERFUMES.

     _Essential Oils--Source and Preparation--Properties--Artificial
     and Synthetic Perfumes._


The number of raw materials, both natural and artificial, at the
disposal of the perfumer, has increased so enormously during recent
years that the scenting of soaps has now become an art requiring very
considerable skill, and a thorough knowledge of the products to be
handled. Not only does the all-important question of odour come into
consideration, but the action of the perfumes on the soap, and on each
other, has also to be taken into account. Thus, many essential oils and
synthetic perfumes cause the soap to darken rapidly on keeping, _e.g._,
clove oil, cassia oil, heliotropin, vanillin. Further, some odoriferous
substances, from their chemical nature, are incompatible with soap, and
soon decompose any soap to which they are added, while in a few cases,
the blending of two unsuitable perfumes results, by mutual reaction, in
the effect of each being lost. In the case of oils like bergamot oil,
the odour value of which depends chiefly on their ester content, it is
very important that these should not be added to soaps containing much
free alkali, as these esters are readily decomposed thereby. Some
perfumes possess the property of helping the soap to retain other and
more delicate odours considerably longer than would otherwise be
possible. Such perfumes are known as "fixing agents" or "fixateurs," and
among the most important of these may be mentioned musk, both natural
and artificial, civet, the oils of Peru balsam, sandalwood, and
patchouli, and benzyl benzoate.

The natural perfumes employed for addition to soaps are almost entirely
of vegetable origin, and consist of essential oils, balsams, and resins,
animal perfumes such as musk, civet, and ambergris being reserved
principally for the preparation of "extraits".

As would be expected with products of such diverse character, the
methods employed for the preparation of essential oils vary
considerably. Broadly speaking, however, the processes may be divided
into three classes--(1) _expression_, used for orange, lemon, and lime
oils; (2) _distillation_, employed for otto of rose, geranium,
sandalwood, and many other oils; and (3) _extraction_, including
_enfleurage_, by which the volatile oil from the flowers is either first
absorbed by a neutral fat such as lard, and then extracted therefrom by
maceration in alcohol, or directly extracted from the flowers by means
of a volatile solvent such as benzene, petroleum ether, or chloroform.
The last process undoubtedly furnishes products most nearly resembling
the natural floral odours, and is the only one which does not destroy
the delicate fragrance of the violet and jasmine. The yield, however, is
extremely small, and concrete perfumes prepared in this way are
therefore somewhat costly.

The essential oils used are derived from upwards of twenty different
botanical families, and are obtained from all parts of the world. Thus,
from Africa we have geranium and clove oils; from America, bay, bois de
rose, Canadian snake root, cedarwood, linaloe, peppermint, petitgrain,
and sassafras; from Asia, camphor, cassia, cinnamon, patchouli,
sandalwood, star anise, ylang-ylang, and the grass oils, _viz._,
citronella, lemongrass, palmarosa, and vetivert; from Australia,
eucalyptus; while in Europe there are the citrus oils, bergamot, lemon,
and orange, produced by Sicily, aspic, lavender, neroli, petitgrain, and
rosemary by France, caraway and clove by Holland, anise by Russia, and
otto of rose by Bulgaria.

Attempts have been made to classify essential oils either on a botanical
basis or according to their chemical composition, but neither method is
very satisfactory, and, in describing the chief constituents and
properties of the more important oils, we have preferred therefore to
arrange them alphabetically, as being simpler for reference.

It is a matter of some difficulty to judge the purity of essential oils,
not only because of their complex nature, but owing to the very great
effect upon their properties produced by growing the plants in different
soils and under varying climatic conditions, and still more to the
highly scientific methods of adulteration adopted by unscrupulous
vendors. The following figures will be found, however, to include all
normal oils.

_Anise Stell_, or _Star Anise_, from the fruit of Illicium verum,
obtained from China. Specific gravity at 15° C., 0.980-0.990; optical
rotation, faintly dextro- or lævo-rotatory, +0° 30' to -2°; refractive
index at 20° C., 1.553-1.555; solidifying point, 14°-17° C.; solubility
in 90 per cent. alcohol, 1 in 3 or 4.

The chief constituents of the oil are anethol, methyl chavicol,
d-pinene, l-phellandrene, and in older oils, the oxidation products of
anethol, _viz._ anisic aldehyde and anisic acid. Since anethol is the
most valuable constituent, and the solidifying point of the oil is
roughly proportional to its anethol content, oils with a higher
solidifying point are the best.

_Aspic oil_, from the flowers of Lavandula spica, obtained from France
and Spain, and extensively employed in perfuming household and cheap
toilet soaps; also frequently found as an adulterant in lavender oil.
Specific gravity at 15° C., 0.904-0.913; optical rotation, French,
dextro-rotatory up to +4°, rarely up to +7°, Spanish, frequently
slightly lævo-rotatory to -2°, or dextro-rotatory up to +7°; esters,
calculated as linalyl acetate, 2 to 6 per cent.; most oils are soluble
in 65 per cent. alcohol 1 in 4, in no case should more than 2.5 volumes
of 70 per cent. alcohol be required for solution.

The chief constituents of the oil are: linalol, cineol, borneol,
terpineol, geraniol, pinene, camphene and camphor.

_Bay oil_, distilled from the leaves of Pimenta acris, and obtained from
St. Thomas and other West Indian Islands. It is used to some extent as a
perfume for shaving soaps, but chiefly in the Bay Rhum toilet
preparation. Specific gravity at 15° C., 0.965-0.980; optical rotation,
slightly lævo-rotatory up to -3°; phenols, estimated by absorption with
5 per cent. caustic potash solution, from 45 to 60 per cent.; the oil is
generally insoluble in 90 per cent. alcohol, though when freshly
distilled it dissolves in its own volume of alcohol of this strength.

The oil contains eugenol, myrcene, chavicol, methyl eugenol, methyl
chavicol, phellandrene, and citral.

_Bergamot oil_, obtained by expression from the fresh peel of the fruit
of Citrus Bergamia, and used very largely for the perfuming of toilet
soaps. Specific gravity at 15° C., 0.880-0.886; optical rotation, +10°
to +20°; esters, calculated as linalyl acetate, 35-40 per cent., and
occasionally as high as 42-43 per cent.; frequently soluble in 1.5 parts
of 80 per cent. alcohol, or failing that, should dissolve in one volume
of 82.5 or 85 per cent. alcohol. When evaporated on the water-bath the
oil should not leave more than 5-6 per cent. residue.

Among the constituents of this oil are: linalyl acetate, limonene,
dipentene, linalol, and bergaptene.

_Bitter Almond Oil._--The volatile oil obtained from the fruit of
_Amygdalus communis_. Specific gravity at 15° C., 1.045-1.06; optically
inactive; refractive index at 20° C., 1.544-1.545; boiling point,
176-177° C.; soluble in 1 or 1.5 volumes of 70 per cent. alcohol.

The oil consists almost entirely of benzaldehyde which may be estimated
by absorption with a hot saturated solution of sodium bisulphite. The
chief impurity is prussic acid, which is not always completely removed.
This may be readily detected by adding to a small quantity of the oil
two or three drops of caustic soda solution, and a few drops of ferrous
sulphate solution containing ferric salt. After thoroughly shaking,
acidulate with dilute hydrochloric acid, when a blue coloration will be
produced if prussic acid is present.

The natural oil may frequently be differentiated from artificial
benzaldehyde by the presence of chlorine in the latter. As there is now
on the market, however, artificial oil free from chlorine, it is no
longer possible, by chemical means, to distinguish with certainty
between the natural and the artificial product. To test for chlorine in
a sample, a small coil of filter paper, loosely rolled, is saturated
with the oil, and burnt in a small porcelain dish, covered with an
inverted beaker, the inside of which is moistened with distilled water.
When the paper is burnt, the beaker is rinsed with water, filtered, and
the filtrate tested for chloride with silver nitrate solution.

_Canada snake root oil_, from the root of Asarum canadense. Specific
gravity at 15° C., 0.940-0.962; optical rotation, slightly lævo-rotatory
up to -4°; refractive index at 20° C., 1.485-1.490; saponification
number, 100-115; soluble in 3 or 4 volumes of 70 per cent. alcohol.

The principal constituents of the oil are a terpene, asarol alcohol,
another alcohol, and methyl eugenol. The oil is too expensive to be used
in other than high-class toilet soaps.

_Cananga_ or _Kananga oil_, the earlier distillate from the flowers of
Cananga odorata, obtained chiefly from the Philippine Islands. Specific
gravity at 15° C., 0.910-0.940; optical rotation, -17° to -30°;
refractive index at 20° C., 1.4994-1.5024; esters, calculated as linalyl
benzoate, 8-15 per cent.; soluble in 1.5 to 2 volumes of 95 per cent.
alcohol, but becoming turbid on further addition.

The oil is qualitatively similar in composition to Ylang-Ylang oil, and
contains linalyl benzoate and acetate, esters of geraniol, cadinene, and
methyl ester of p-cresol.

_Caraway oil_, distilled from the seeds of Carum carui. Specific gravity
at 15° C., 0.907-0.915; optical rotation, +77° to +79°; refractive index
at 20° C., 1.485-1.486; soluble in 3 to 8 volumes of 80 per cent.
alcohol. The oil should contain 50-60 per cent. of carvone, which is
estimated by absorption with a saturated solution of neutral sodium
sulphite. The remainder of the oil consists chiefly of limonene.

_Cassia oil_, distilled from the leaves of Cinnamomum cassia, and
shipped to this country from China in lead receptacles. Specific gravity
at 15° C., 1.060-1.068; optical rotation, slightly dextro-rotatory up to
+3° 30'; refractive index at 20° C., 1.6014-1.6048; soluble in 3 volumes
of 70 per cent. alcohol as a general rule, but occasionally requires 1
to 2 volumes of 80 per cent. alcohol.

The value of the oil depends upon its aldehyde content, the chief
constituent being cinnamic aldehyde. This is determined by absorption
with a hot saturated solution of sodium bisulphite. Three grades are
usually offered, the best containing 80-85 per cent. aldehydes, the
second quality, 75-80 per cent., and the lowest grade, 70-75 per cent.

Other constituents of the oil are cinnamyl acetate and cinnamic acid.
This oil gives the characteristic odour to Brown Windsor soap, and is
useful for sweetening coal-tar medicated soaps.

_Cedarwood oil_, distilled from the wood of Juniperus virginiana.
Specific gravity at 15° C., 0.938-0.960; optical rotation, -35° to -45°;
refractive index at 20° C., 1.5013-1.5030. The principal constituents
are cedrene and cedrol.

_Cinnamon oil_, distilled from the bark of Cinnamomum zeylanicum.
Specific gravity at 15° C., 1.00-1.035; optical rotation, lævo-rotatory
up to -2°; usually soluble in 2 to 3 volumes of 70 per cent. alcohol,
but sometimes requires 1 volume of 80 per cent. alcohol for solution;
aldehydes, by absorption with sodium bisulphite solution, 55-75 per
cent.; and phenols, as measured by absorption with 5 per cent. potash,
not exceeding 12 per cent.

The value of this oil is not determined entirely by its aldehyde content
as is the case with cassia oil, and any oil containing more than 75 per
cent. aldehydes must be regarded with suspicion, being probably admixed
with either cassia oil or artificial cinnamic aldehyde. The addition of
cinnamon leaf oil which has a specific gravity at 15° C. of 1.044-1.065
is detected by causing a material rise in the proportion of phenols.
Besides cinnamic aldehyde the oil contains eugenol and phellandrene.

_Citronella Oil._--This oil is distilled from two distinct Andropogon
grasses, the Lana Batu and the Maha pangiri, the former being the source
of the bulk of Ceylon oil, and the latter being cultivated in the
Straits Settlements and Java. The oils from these three localities show
well-defined chemical differences.

_Ceylon Citronella oil_ has the specific gravity at 15° C., 0.900-0.920;
optical rotation, lævo-rotatory up to -12°; refractive index at 20° C.,
1.480-1.484; soluble in 1 volume of 80 per cent. alcohol; total
acetylisable constituents, calculated as geraniol, 54-70 per cent.

_Singapore Citronella Oil._--Specific gravity at 15° C., 0.890-0.899;
optical rotation, usually slightly lævo-rotatory up to -3°; refractive
index at 20° C., 1.467-1.471; soluble in 1 to 1.5 volumes of 80 per
cent. alcohol; total acetylisable constituents, calculated as geraniol,
80-90 per cent.

_Java Citronella Oil._--Specific gravity at 15° C., 0.890-0.901; optical
rotation, -1° to -6°; total acetylisable constituents, calculated as
geraniol, 75-90 per cent.; soluble in 1-2 volumes of 80 per cent.
alcohol.

The chief constituents of the oil are geraniol, citronellal, linalol,
borneol, methyl eugenol, camphene, limonene, and dipentene. It is very
largely used for perfuming cheap soaps, and also serves as a source for
the production of geraniol.

_Bois de Rose Femelle oil_, or _Cayenne linaloe oil_, distilled from
wood of trees of the Burseraceæ species. Specific gravity at 15° C.,
0.874-0.880; optical rotation, -11° 30' to -16°; refractive index at 20°
C., 1.4608-1.4630; soluble in 1.5 to 2 volumes of 70 per cent. alcohol.

The oil consists almost entirely of linalol, with traces of saponifiable
bodies, but appears to be free from methyl heptenone, found by Barbier
and Bouveault in Mexican linaloe oil. This oil is distinctly finer in
odour than the Mexican product.

_Clove oil_, distilled from the unripe blossoms of Eugenia
caryophyllata, the chief source of which is East Africa (Zanzibar and
Pemba). Specific gravity at 15° C., 1.045-1.061; optical rotation,
slightly lævo-rotatory up to -1° 30'; phenols, estimated by absorption
with 5 per cent. potash solution, 86-92 per cent.; refractive index at
20° C., 1.5300-1.5360; soluble in 1 to 2 volumes of 70 per cent.
alcohol.

The principal constituent of the oil is eugenol, together with
caryophyllene and acet-eugenol. While within certain limits the value of
this oil is determined by its eugenol content, oils containing more than
93 per cent. phenols are usually less satisfactory in odour, the high
proportion of phenols being obtained at the expense of the decomposition
of some of the sesquiterpene. Oils with less than 88 per cent. phenols
will be found somewhat weak in odour. This oil is extensively used in
the cheaper toilet soaps and is an important constituent of carnation
soaps. As already mentioned, however, it causes the soap to darken in
colour somewhat rapidly, and must not therefore be used in any quantity,
except in coloured soaps.

_Concrete orris oil_, a waxy substance obtained by steam distillation of
Florentine orris root.

Melting point, 35-45° C., usually 40-45° C.; free acidity, calculated as
myristic acid, 50-80 per cent.; ester, calculated as combined myristic
acid, 4-10 per cent.

The greater part of the product consists of the inodorous myristic acid,
the chief odour-bearing constituent being irone. The high price of the
oil renders its use only possible in the very best quality soaps.

_Eucalyptus Oil._--Though there are some hundred or more different oils
belonging to this class, only two are of much importance to the
soap-maker. These are:--

(i.) Eucalyptus citriodora. Specific gravity at 15° C., 0.870-0.905;
optical rotation, slightly dextro-rotatory up to +2°; soluble in 4-5
volumes of 70 per cent. alcohol.

The oil consists almost entirely of citronellic aldehyde, and on
absorption with saturated solution of sodium bisulphite should leave
very little oil unabsorbed.

(ii.) Eucalyptus globulus, the oil used in pharmacy, and containing
50-65 per cent. cineol. Specific gravity at 15° C., 0.910-0.930; optical
rotation, +1° to +10°; soluble in 2 to 3 parts of 70 per cent. alcohol;
cineol (estimated by combination with phosphoric acid, pressing,
decomposing with hot water, and measuring the liberated cineol), not
less than 50 per cent. Besides cineol, the oil contains d-pinene, and
valeric, butyric, and caproic aldehydes. It is chiefly used in medicated
soaps.

_Fennel (sweet) oil_, obtained from the fruit of Foeniculum vulgare,
grown in Germany, Roumania, and other parts of Europe. Specific gravity
at 15° C., 0.965-0.985; optical rotation, +6° to +25°; refractive index
at 20° C., 1.515-1.548; usually soluble in 2-6 parts 80 per cent.
alcohol, but occasionally requires 1 part of 90 per cent. alcohol.

The chief constituents of the oil are anethol, fenchone, d-pinene, and
dipentene.

_Geranium oils_, distilled from plants of the Pelargonium species.
There are three principal kinds of this oil on the market--the African,
obtained from Algeria and the neighbourhood, the Bourbon, distilled
principally in the Island of Réunion, and the Spanish. The oil is also
distilled from plants grown in the South of France, but this oil is not
much used by soap-makers. A specially fine article is sold by a few
essential oil firms under the name of "Geranium-sur-Rose," which as its
name implies, is supposed to be geranium oil distilled over roses. This
is particularly suitable for use in high-class soaps. The following are
the general properties of these oils. It will be seen that the limits
for the figures overlap to a considerable extent.

 _________________________________________________________________________
|                         |           |           |           |           |
|                         |  African. |  Bourbon. |  Spanish. |  French.  |
|_________________________|___________|___________|___________|___________|
|                         |           |           |           |           |
| Specific gravity        |           |           |           |           |
|   at 15° C.             | .890-.900 | .888-.895 | .895-.898 | .897-.900 |
| Optical rotation.       |-6° to -10°|-9° to -18°|-8° to -11°|-8° to -11°|
| Esters, calculated as   |   20-27   |   27-32   |   20-27   |   18-23   |
|   geranyl tiglate       | per cent. | per cent. | per cent. | per cent. |
| Total alcohols, as      |   68-75   |   70-80   |   65-75   |   66-75   |
|   geraniol.             | per cent. | per cent. | per cent. | per cent. |
| Solubility in 70 per    |           |           |           |           |
|   cent. alcohol.        | 1 in 1.5-2| 1 in 1.5-2| 1 in 2-3  | 1 in 1.5-2|
|_________________________|___________|___________|___________|___________|

The oil contains geraniol and citronellol, both free, and combined with
tiglic, valeric, butyric, and acetic acids; also l-menthone. The African
and Bourbon varieties are the two most commonly used for
soap-perfurmery, the Spanish oil being too costly for extensive use.

_Ginger-grass oil_, formerly regarded as an inferior kind of palma-rosa
but now stated to be from an entirely different source. Specific gravity
at 15° C., 0.889-0.897; optical rotation, +15°.

The oil contains a large amount of geraniol, together with di-hydrocumin
alcohol, d-phellandrene, d-limonene, dipentene, and l-carvone.

_Guaiac wood oil_, distilled from the wood of Bulnesia sarmienti.
Specific gravity at 30° C., 0.967-0.975; optical rotation, -4° 30' to
-7°; refractive index at 20° C., 1.506-1.507; soluble in 3 to 5 volumes
of 70 per cent. alcohol.

The principal constituent of the oil is guaiac alcohol, or gusiol. This
oil, which has what is generally termed a "tea-rose odour," is
occasionally used as an adulterant for otto of rose.

_Lavender oil_, distilled from the flowers of Lavandula vera, grown in
England, France, Italy and Spain. The English oil is considerably the
most expensive, and is seldom, if ever, used in soap. The French and
Italian oils are the most common, the Spanish oil being a comparatively
new article, of doubtful botanical origin, and more closely resembling
aspic oil.

English Oil.--Specific gravity at 15° C., 0.883-0.900; optical rotation,
-4° to -10°; esters, calculated as linalyl acetate, 5-10 per cent.;
soluble in 3 volumes of 70 per cent. alcohol.

French and Italian Oils.--Specific gravity at 15° C., 0.885-0.900;
optical rotation, -2° to -9°; refractive index at 20° C., 1.459-1.464;
esters, calculated as linalyl acetate, 20-40 per cent., occasionally
higher; soluble in 1.5-3 volumes of 70 per cent. alcohol.

There was at one time a theory that the higher the proportion of ester
the better the oil, but this theory has now to a very large extent
become discredited, and there is no doubt that some of the finest oils
contain less than 30 per cent. of esters.

Spanish Oil.--Specific gravity at 15° C., 0.900-0.915; optical rotation,
-2° to +7°; esters, calculated as linalyl acetate, 2-6 per cent.;
soluble in 1-2 volumes of 70 per cent. alcohol.

The chief constituents of lavender oil are linalyl acetate, linalol,
geraniol, and linalyl butyrate, while the English oil also contains a
distinct amount of cineol.

_Lemon oil_, prepared by expressing the peel of the nearly ripe fruit of
Citrus limonum, and obtained almost entirely from Sicily and Southern
Italy. Specific gravity at 15° C., 0.856-0.860; optical rotation, +58°
to +63°; refractive index at 20° C., 1.4730-1.4750; aldehydes (citral),
2.5 to 4 per cent.

The principal constituents of the oil are limonene and citral, together
with small quantities of pinene, phellandrene, octyl and nonyl
aldehydes, citronellal, geraniol, geranyl acetate, and the stearopten,
citraptene.

_Lemon-grass_ (so-called _verbena_) oil, distilled from the grass
Andropogon citratus, which is grown in India and, more recently, in the
West Indies. The oils from these two sources differ somewhat in their
properties, and also in value, the former being preferred on account of
its greater solubility in alcohol.

East Indian.--Specific gravity at 15° C., 0.898-0.906; optical rotation,
-0° 30' to -6°; aldehydes, by absorption with bisulphite of soda
solution, 65 to 78 per cent.; refractive index at 20° C., 1.485-1.487;
soluble in 2-3 volumes of 70 per cent. alcohol.

West Indian.--Specific gravity at 15° C., 0.886-0.893; optical rotation,
faintly lævo-gyrate; refractive index at 20° C., 1.4855-1.4876; soluble
in 0.5 volume of 90 per cent. alcohol.

_Lime oil_, obtained by expression or distillation of the peel of the
fruit of Citrus medica, and produced principally in the West Indies.

Expressed Oil.--Specific gravity at 15° C., 0.870-0.885; optical
rotation, +38° to +50°. Its most important constituent is citral.

Distilled Oil.--This is entirely different in character to the expressed
oil. Its specific gravity at 15° C. is 0.854-0.870; optical rotation,
+38° to +54°; soluble in 5-8 volumes of 90 per cent. alcohol.

_Linaloe oil_, distilled from the wood of trees of the Burseraceæ
family, and obtained from Mexico. Specific gravity at 15° C.,
0.876-0.892; optical rotation, usually lævo-rotatory, -3° to -13°, but
occasionally dextro-rotatory up to +5° 30'; esters, calculated as
linalyl acetate, 1-8 per cent.; total alcohols as linalol, determined by
acetylation, 54-66 per cent.; soluble in 1-2 volumes of 70 per cent.
alcohol.

This oil consists mainly of linalol, together with small quantities of
methyl heptenone, geraniol, and d-terpineol.

_Marjoram oil_, distilled from Origanum majoranoides, and obtained
entirely from Cyprus. Specific gravity at 15° C., 0.966; phenols,
chiefly carvacrol, estimated by absorption with 5 per cent. caustic
potash solution, 80-82 per cent.; soluble in 2-3 volumes of 70 per cent.
alcohol.

This oil is used in soap occasionally in place of red thyme oil.

_Neroli Bigarade oil_, distilled from the fresh blossoms of the bitter
orange, Citrus bigaradia. Specific gravity at 15° C., 0.875-0.882;
optical rotation, +0° 40' to +10°, and occasionally much higher;
refractive index at 20° C., 1.468-1.470; esters, calculated as linalyl
acetate, 10-18 per cent.; soluble in 0.75-1.75 volumes of 80 per cent.
alcohol, becoming turbid on further addition of alcohol.

The chief constituents of the oil are limonene, linalol, linalyl
acetate, geraniol, methyl anthranilate, indol, and neroli camphor.

_Orange (sweet) oil_, expressed from the peel of Citrus aurantium.
Specific gravity at 15° C., 0.849-0.852; optical rotation, +95° to +99°;
refractive index at 20° C., 1.4726-1.4732.

The oil contains some 90 per cent. limonene, together with nonyl
alcohol, d-linalol, d-terpineol, citral, citronellal, decyl aldehyde,
and methyl anthranilate.

_Palmarosa_, or _East Indian geranium oil_, distilled from Andropogon
Schoenanthus, a grass widely grown in India. Specific gravity at 15°
C., 0.888-0.895; optical rotation, +1° to -3°; refractive index at 20°
C., 1.472-1.476; esters, calculated as linalyl acetate, 7-14 per cent.;
total alcohols, as geraniol, 75-93 per cent.; solubility in 70 per cent.
alcohol, 1 in 3.

The oil consists chiefly of geraniol, free, and combined with acetic and
caproic acids, and dipentene. It is largely used in cheap toilet soaps,
particularly in rose soaps. It is also a favourite adulterant for otto
of rose, and is used as a source of geraniol.

_Patchouli oil_, distilled from the leaves of Pogostemon patchouli, a
herb grown in India and the Straits Settlements. Specific gravity at 15°
C., 0.965-0.990; optical rotation, -45° to -63°; refractive index at 20°
C., 1.504-1.511; saponification number, up to 12; sometimes soluble in
0.5 to 1 volume of 90 per cent. alcohol, becoming turbid on further
addition. The solubility of the oil in alcohol increases with age. The
oil consists to the extent of 97 per cent. of patchouliol and cadinene,
which have little influence on its odour, and the bodies responsible for
its persistent and characteristic odour have not yet been isolated.

_Peppermint oil_, distilled from herbs of the Mentha family, the
European and American from Mentha piperita, and the Japanese being
generally supposed to be obtained from Mentha arvensis. The locality in
which the herb is grown has a considerable influence on the resulting
oil, as the following figures show:--

English.--Specific gravity at 15° C., 0.900-0.910; optical rotation,
-22° to -33°; total menthol, 55-66 per cent.; free menthol, 50-60 per
cent.; soluble in 3-5 volumes of 70 per cent. alcohol.

American.--Specific gravity at 15° C., 0.906-0.920; optical rotation,
-20° to -33°; total menthol, 50-60 per cent.; free menthol, 40-50 per
cent. The Michigan oil is soluble in 3-5 volumes of 70 per cent.
alcohol, but the better Wayne County oil usually requires 1-2 volumes of
80 per cent. alcohol, and occasionally 0.5 volume of 90 per cent.
alcohol.

French.--Specific gravity at 15° C., 0.917-0.925; optical rotation, -6°
to -10°; total menthol, 45-55 per cent.; free menthol, 35-45 per cent.;
soluble in 1 to 1.5 volumes of 80 per cent.

Japanese.--Specific gravity at 25° C., 0.895-0.900; optical rotation,
lævo-rotatory up to -43°; solidifies at 17 to 27° C.; total menthol,
70-90 per cent., of which 65-85 per cent. is free; soluble in 3-5
volumes of 70 per cent. alcohol.

The dementholised oil is fluid at ordinary temperatures, has a specific
gravity of 0.900-0.906 at 15° C., and contains 50-60 per cent. total
menthol.

Some twenty different constituents have been found in American
peppermint oil, including menthol, menthone, menthyl acetate, cineol,
amyl alcohol, pinene, l-limonene, phellandrene, dimethyl sulphide,
menthyl isovalerianate, isovalerianic aldehyde, acetaldehyde, acetic
acid, and isovalerianic acid.

_Peru balsam oil_, the oily portion (so-called "cinnamein") obtained
from Peru balsam. Specific gravity at 15° C., 1.100-1.107; optical
rotation, slightly dextro-rotatory up to +2°; refractive index at 20°
C., 1.569 to 1.576; ester, calculated as benzyl benzoate, 80-87 per
cent.; soluble in 1 volume of 90 per cent. alcohol.

The oil consists chiefly of benzyl benzoate and cinnamate, together with
styracin, or cinnamyl cinnamate, and a small quantity of free benzoic
and cinnamic acids.

_Petitgrain oil_, obtained by distillation of the twigs and unripe fruit
of Citrus bigaradia. There are two varieties of the oil, the French and
the South American, the former being the more valuable. Specific gravity
at 15° C., 0.886-0.900; optical rotation, -3° to +6°; refractive index
at 20° C., 1.4604-1.4650; esters, calculated as linalyl acetate, 40-55
per cent., for the best qualities usually above 50 per cent.; soluble as
a rule in 2-3 volumes of 70 per cent. alcohol, but occasionally requires
1-2 volumes of 80 per cent. alcohol.

Among its constituents are limonene, linalyl acetate, geraniol and
geranyl acetate.

_Pimento oil_ (allspice), distilled from the fruit of Pimenta
officinalis, which is found in the West Indies and Central America.
Specific gravity at 15° C., 1.040-1.060; optical rotation, slightly
lævo-rotatory up to -4°; refractive index at 20° C., 1.529-1.536;
phenols, estimated by absorption with 5 per cent. potash solution,
68-86 per cent.; soluble in 1-2 volumes of 70 per cent. alcohol.

The oil contains eugenol, methyl eugenol, cineol, phellandrene, and
caryophyllene.

_Rose oil (otto of rose)_, distilled from the flowers of Rosa damascena,
though occasionally the white roses (Rosa alba) are employed. The
principal rose-growing district is in Bulgaria, but a small quantity of
rose oil is prepared from roses grown in Anatolia, Asia Minor. An
opinion as to the purity of otto of rose can only be arrived at after a
very full chemical analysis, supplemented by critical examination of its
odour by an expert. The following figures, however, will be found to
include most oils which can be regarded as genuine. Specific gravity at
30° C., 0.850-0.858; optical rotation at 30° C., -1° 30' to -3°;
refractive index at 20° C., 1.4600-1.4645; saponification value, 7-11;
solidifying point, 19-22° C.; iodine number, 187-194; stearopten
content, 14-20 per cent.; melting point of stearopten, about 32° C.

A large number of constituents have been isolated from otto of rose,
many of which are, however, only present in very small quantities. The
most important are geraniol, citronellol, phenyl ethyl alcohol, together
with nerol, linalol, citral, nonylic aldehyde, eugenol, a sesquiterpene
alcohol, and the paraffin stearopten.

_Rosemary oil_, distilled from the herb Rosemarinus officinalis, and
obtained from France, Dalmatia, and Spain. The herb is also grown in
England, but the oil distilled therefrom is rarely met with in commerce.
The properties of the oils vary with their source, and also with the
parts of the plant distilled, distillation of the stalks as well as the
leaves tending to reduce the specific gravity and borneol content, and
increase the proportion of the lævo-rotatory constituent (lævo-pinene).
The following figures may be taken as limits for pure oils:--

French and Dalmatian.--Specific gravity at 15° C., 0.900-0.916; optical
rotation, usually dextro-rotatory, up to +15°, but may occasionally be
lævo-rotatory, especially if stalks have been distilled with the leaves;
ester, calculated as bornyl acetate, 1-6 per cent.; total borneol, 12-18
per cent.; usually soluble in 1-2 volumes of 82.5 per cent. alcohol.

Spanish.--The properties of the Spanish oil are similar to the others,
except that it is more frequently lævo-rotatory.

Rosemary oil contains pinene, camphene, cineol, borneol, and camphor.

_Sandalwood oil_, obtained by distillation of the wood of Santalum album
(East Indian), Santalum cygnorum (West Australian), and Amyris
balsamifera (West Indian). The oils obtained from these three different
sources differ very considerably in value, the East Indian being by far
the best.

East Indian.--Specific gravity at 15° C., 0.975-0.980; optical rotation,
-14° to -20°; refractive index at 20° C., 1.5045-1.5060; santalol,
92-97 per cent.; usually soluble in 4-6 volumes of 70 per cent. alcohol,
though, an old oil occasionally is insoluble in 70 per cent. alcohol.

West Australian.--Specific gravity at 15° C., 0.950-0.968; optical
rotation, +5° to +7°; alcohols, calculated as santalol, 73-75 per cent.;
insoluble in 70 per cent. alcohol, but readily dissolves in 1-2 volumes
of 80 per cent. alcohol.

West Indian.--Specific gravity at 15° C., 0.948-0.967; optical rotation,
+13° 30' to +30°; insoluble in 70 per cent. alcohol.

In addition to free santalol, the oil contains esters of santalol and
santalal.

_Sassafras oil_, distilled from the bark of Sassafras officinalis, and
obtained chiefly from America. Specific gravity at 15° C., 1.06-1.08;
optical rotation, +1° 50' to +4°; refractive index at 20° C.,
1.524-1.532; soluble in, 6-10 volumes of 85 per cent. alcohol,
frequently soluble in 10-15 volumes of 80 per cent. alcohol.

The chief constituents are safrol, pinene, eugenol, camphor, and
phellandrene. The removal of safrol, either intentionally or by
accident, owing to cooling of the oil and consequent deposition of the
safrol, is readily detected by the reduction of the specific gravity
below 1.06.

_Thyme oil, red and white_, distilled from the green or dried herb,
Thymus vulgaris, both French and Spanish oils being met with. These oils
are entirely different in character.

French.--Specific gravity at 15° C., 0.91-0.933; slightly lævo-rotatory
up to -4°, but usually too dark to observe; phenols, by absorption with
10 per cent. aqueous caustic potash, 25-55 per cent.; refractive index
at 20° C., 1.490-1.500; soluble in 1-1.5 volumes of 80 per cent.
alcohol.

Spanish.--Specific gravity at 15° C., 0.955-0.966; optical rotation,
slightly lævo-gyrate; phenols, 70-80 per cent.; refractive index at 20°
C.; 1.5088-1.5122; soluble in 2-3 volumes of 70 per cent. alcohol.

In addition to the phenols, thymol or carvacrol, these oils contain
cymene, thymene and pinene.

The white thyme oil is produced by rectifying the red oil, which is
generally effected at the expense of a considerable reduction in phenol
content, and hence in real odour value of the oil.

_Verbena Oil._--The oil usually sold under this name is really
lemon-grass oil (which see _supra_). The true verbena oil or French
verveine is, however, occasionally met with. This is distilled in France
from the verbena officinalis, and has the following properties: Specific
gravity at 15° C., 0.891-0.898; optical rotation, slightly dextro- or
lævo-rotatory; aldehydes, 70-75 per cent.; soluble in 2 volumes of 70
per cent. alcohol.

The oil contains citral.

_Vetivert oil_, distilled from the grass, Andropogon muricatus, or Cus
Cus, and grown in the East Indies.

Specific gravity at 15° C., 1.01-1.03; optical rotation, +20° to +26°;
saponification number, 15-30; refractive index at 20° C., 1.521-1.524;
soluble in 2 volumes of 80 per cent. alcohol.

The price of this oil makes its use prohibitive except in the highest
class soaps.

_Wintergreen Oil._--There are two natural sources of this oil, the
Gaultheria procumbens and the Betula lenta. Both oils consist almost
entirely of methyl salicylate and are practically identical in
properties, the chief difference being that the former has a slight
lævo-rotation, while the latter is inactive.

Specific gravity at 15° C., 1.180-1.187; optical rotation, Gaultheria
oil, up to -1°, Betula oil, inactive; ester as methyl salicylate, at
least 98 per cent.; refractive index at 20° C., 1.5354-1.5364; soluble
in 2-6 volumes of 70 per cent. alcohol.

Besides methyl salicylate, the oil contains triaconitane, an aldehyde or
ketone, and an alcohol.

_Ylang-ylang oil_, distilled from the flowers of Cananga odorata, the
chief sources being the Philippine Islands and Java. Specific gravity at
15° C., 0.924-0.950; optical rotation, -30° to -60°, and occasionally
higher; refractive index at 20° C., 1.496-1.512; ester, calculated as
linalyl benzoate, 27-45 per cent., occasionally up to 50 per cent.;
usually soluble in 1/2 volume of 90 per cent. alcohol.

The composition of the oil is qualitatively the same as that of Cananga
oil, but it is considerably more expensive and therefore can only be
used in the highest grade soaps.


_Artificial and Synthetic Perfumes._

During the past few years the constitution of essential oils has been
studied by a considerable number of chemists, and the composition of
many oils has been so fully determined that very good imitations can
often be made at cheaper prices than those of the genuine oils,
rendering it possible to produce cheap soaps having perfumes which were
formerly only possible in the more expensive article.

There is a considerable distinction, however, often lost sight of,
between an _artificial_ and a _synthetic_ oil. An artificial oil may be
produced by separating various constituents from certain natural oils,
and so blending these, with or without the addition of other substances,
as to produce a desired odour, the perfume being, at any rate in part,
obtained from natural oils. A synthetic perfume, on the other hand, is
entirely the product of the chemical laboratory, no natural oil or
substance derived therefrom entering into its composition.

The following are among the most important bodies of this class:--

_Amyl salicylate_, the ester prepared from amyl alcohol and salicylic
acid, sometimes known as "Orchidée" or "Trèfle". This is much used for
the production of a clover-scented soap. It has the specific gravity at
15° C., 1.052-1.054; optical rotation, +1° 16' to +1° 40'; refractive
index at 20° C., 1.5056; and should contain not less than 97 per cent.
ester, calculated as amyl salicylate.

_Anisic aldehyde_, or _aubépine_, prepared by oxidation of anethol, and
possessing a pleasant, hawthorn odour. This has the specific gravity at
15° C., 1.126; refractive index at 20° C., 1.5693; is optically
inactive, and dissolves readily in one volume of 70 per cent. alcohol.

_Benzyl Acetate_, the ester obtained from benzyl alcohol and acetic
acid. This has a very strong and somewhat coarse, penetrating odour,
distinctly resembling jasmine. Its specific gravity at 15° C. is
1.062-1.065; refractive index at 20° C., 1.5020; and it should contain
at least 97-98 per cent. ester, calculated as benzyl acetate.

_Citral_, the aldehyde occurring largely in lemon-grass and verbena
oils, also to a less extent in lemon and orange oils, and possessing an
intense lemon-like odour. It has a specific gravity at 15° C.,
0.896-0.897, is optically inactive, and should be entirely absorbed by a
hot saturated solution of sodium bisulphite.

_Citronellal_, an aldehyde possessing the characteristic odour of
citronella oil, in which it occurs to the extent of about 20 per cent.,
and constituting considerably over 90 per cent. of eucalyptus citriodora
oil. Its specific gravity at 15° C. is 0.862; refractive index at 20°
C., 1.447; optical rotation, +8° to +12°; and it should be entirely
absorbed by a hot saturated solution of sodium bisulphite.

_Coumarin_, a white crystalline product found in Tonka beans, and
prepared synthetically from salicylic acid. It has an odour resembling
new-mown hay, and melts at 67° C.

_Geraniol_, a cyclic alcohol, occurring largely in geranium, palma-rosa,
and citronella oils. Its specific gravity at 15° C. is 0.883-0.885;
refractive index at 20° C., 1.4762-1.4770; it is optically inactive, and
boils at 218°-225° C.

_Heliotropin_, which possesses the characteristic odour of heliotrope,
is prepared artificially from safrol. It crystallises in small prisms
melting at 86° C.

_Hyacinth._--Most of the articles sold under this name are secret blends
of the different makers. Styrolene has an odour very much resembling
hyacinth, and probably forms the basis of most of these preparations,
together with terpineol, and other artificial bodies. The properties of
the oil vary considerably for different makes.

_Ionone_, a ketone first prepared by Tiemann, and having when diluted a
pronounced violet odour. It is prepared by treating a mixture of citral
and acetone with barium hydrate, and distilling in vacuo. Two isomeric
ketones, [alpha]-ionone and [beta]-ionone, are produced, the article
of commerce being usually a mixture of both. The two ketones have the
following properties:--

Alpha-ionone.--Specific gravity at 15° C., 0.9338; refractive index at
16.5 C., 1.50048 (Chuit); optically it is inactive.

Beta-ionone.--Specific gravity at 15° C., 0.9488; refractive index at
16.8° C., 1.52070 (Chuit); optically it is inactive also.

The product is usually sold in 10 or 20 per cent. alcoholic solution
ready for use.

_Jasmine._--This is one of the few cases in which the artificial oil is
probably superior to that obtained from the natural flowers, possibly
due to the extreme delicacy of the odour, and its consequent slight
decomposition during preparation from the flowers. The chemical
composition of the floral perfume has been very exhaustively studied,
and the artificial article now on the market may be described as a
triumph of synthetical chemistry. Among its constituents are benzyl
acetate, linalyl acetate, benzyl alcohol, indol, methyl anthranilate,
and a ketone jasmone.

_Linalol_, the alcohol forming the greater part of linaloe and bois de
rose oils, and found also in lavender, neroli, petitgrain, bergamot, and
many other oils. The article has the specific gravity at 15° C.,
0.870-0.876; optical rotation, -12° to -14°; refractive index at 20° C.,
1.463-1.464; and when estimated by acetylation, yields about 70 per
cent. of alcohols.

_Linalyl acetate_, or _artificial bergamot oil_, is the ester formed
when linalol is treated with acetic anhydride. It possesses a
bergamot-like odour, but it is doubtful whether its value is
commensurate with its greatly increased price over that of ordinary
bergamot oil. It has the specific gravity at 15° C., 0.912.

_Musk (Artificial)._--Several forms of this are to be obtained,
practically all of which are nitro-derivatives of aromatic hydrocarbons.
The original patent of Baur, obtained in 1889, covered the
tri-nitro-derivative of tertiary butyl xylene. The melting point of the
pure article usually lies between 108° and 112° C., and the solubility
in 95 per cent. alcohol ranges from 1 in 120 to 1 in 200, though more
soluble forms are also made.

An important adulterant, which should always be tested for, is
acetanilide (antifebrin), which may be detected by the characteristic
isocyanide odour produced when musk containing this substance is boiled
with alcoholic potash, and a few drops of chloroform added. Acetanilide
also increases the solubility in 95 per cent. alcohol.

_Neroli Oil (Artificial)._--Like jasmine oil, the chemistry of neroli
oil is now very fully known, and it is therefore possible to prepare an
artificial product which is a very good approximation to the natural
oil, and many such are now on the market, which, on account of their
comparative cheapness, commend themselves to the soap-perfumer. These
consist chiefly of linalol, geraniol, linalyl acetate, methyl
anthranilate, and citral.

_Mirbane Oil_ or _Nitrobenzene._--This is a cheap substitute for oil of
bitter almonds, or benzaldehyde, and is a very coarse, irritating
perfume, only suitable for use in the very cheapest soaps. It is
prepared by the action of a mixture of nitric and sulphuric acids on
benzene at a temperature not exceeding 40° C. Its specific gravity is
1.205-1.206; refractive index at 20° C., 1.550; and boiling point, 206°
C.

_Niobe oil_, or _ethyl benzoate_, the ester obtained from ethyl alcohol
and benzoic acid, and having the specific gravity at 15° C.,
1.094-1.095; refractive index at 20° C., 1.5167; boiling point,
196.5°-198° C.; soluble in 1.5 volumes of 70 per cent. alcohol.

_Oeillet_ is a combination possessed of a sweet carnation-like odour and
having as a basis, eugenol or isoeugenol. Its properties vary with the
source of supply.

_Rose Oil (Artificial)._--Several good and fairly cheap artificial rose
oils are now obtainable, consisting chiefly of citronellol, geraniol,
linalol, phenyl ethyl alcohol, and citral. In some cases stearopten or
other wax is added, to render the oil more similar in appearance to the
natural article, but as these are inodorous, no advantage is gained in
this way, and there is, further, the inconvenience in cold weather of
having to first melt the oil before use.

_Safrol_, an ether which is the chief constituent of sassafras oil, and
also found in considerable quantity in camphor oil. It is sold as an
artificial sassafras oil, and is very much used in perfuming cheap
toilet or household soaps. Its specific gravity at 15° C. is
1.103-1.106; refractive index at 20° C., 1.5373; and it dissolves in
fifteen volumes of 80 per cent. alcohol.

_Santalol_, the alcohol or mixture of alcohols obtained from sandalwood
oil. Its specific gravity at 15° C. is 0.9795; optical rotation, -18°;
and refractive index at 20° C., 1.507.

_Terebene_, a mixture of dipentene and other hydrocarbons prepared from
turpentine oil by treatment with concentrated sulphuric acid, is used
chiefly in medicated soaps. Its specific gravity at 15° C. is
0.862-0.868; the oil is frequently slightly dextro- or lævo-rotatory;
the refractive index at 20° C., 1.470-1.478.

_Terpineol_, an alcohol also prepared from turpentine oil by the action
of sulphuric acid, terpene hydrate being formed as an intermediate
substance. It has a distinctly characteristic lilac odour, and on
account of its cheapness is much used in soap perfumery, especially for
a lilac or lily soap. Its specific gravity at 15° C. is 0.936-0.940;
refractive index at 20° C., 1.4812-1.4835; and boiling point about
210°-212° C. It is optically inactive, and readily soluble in 1.5
volumes of 70 per cent. alcohol.

_Vanillin_, a white crystalline solid, melting at 80°-82° C. and
prepared by the oxidation of isoeugenol. It has a strong characteristic
odour, and occurs, associated with traces of benzoic acid and
heliotropin, in the vanilla bean. It can only be used in small quantity
in light-coloured soaps, as it quickly tends to darken the colour of the
soap.



CHAPTER IX.

GLYCERINE MANUFACTURE AND PURIFICATION.

     _Treatment of Lyes--Evaporation to Crude
     Glycerine--Distillation--Distilled and Dynamite
     Glycerine--Chemically Pure Glycerine--Animal Charcoal for
     Decolorisation--Glycerine obtained by other Methods of
     Saponification--Yield of Glycerine from Fats and Oils._


As pointed out in Chapter II. the fatty acids, which, combined with soda
or potash, form soap, occur in nature almost invariably in the form of
glycerides, _i.e._, compounds of fatty acids with glycerol, and as the
result of saponification of a fat or oil glycerine is set free.

In Chapter V. processes of soap-making are described in which (1) the
glycerine is retained in the finished soap, and (2) the glycerine is
contained in the lyes, in very dilute solution, contaminated with salt
and other impurities. These lyes, though now constituting the chief
source of profit in the manufacture of cheap soaps, were till early in
last century simply run down the drains as waste liquor.

Much attention has been devoted to the purification and concentration of
glycerine lyes; and elaborate plant of various forms has been devised
for the purpose.

_Treatment of Lyes._--The spent lyes withdrawn from the soap-pans are
cooled, and the soap, which has separated during the cooling, is
carefully removed and returned to the soap-house for utilisation in the
manufacture of brown soap. Spent lyes may vary in their content of
glycerol from 3 to 8 per cent., and this depends not only upon the
system adopted in the working of the soap-pans, but also upon the
materials used. Although, in these days of pure caustic soda, spent lyes
are more free from impurities than formerly, the presence of sulphides
and sulphites should be carefully avoided, if it is desired to produce
good glycerine.

The lyes are transferred to a lead-lined tank of convenient size, and
treated with commercial hydrochloric acid and aluminium sulphate,
sufficient being added of the former to neutralise the free alkali, and
render the liquor faintly acid, and of the latter to completely
precipitate the fatty acids. The acid should be run in slowly, and the
point when enough has been added, is indicated by blue litmus paper
being slightly reddened by the lyes.

The whole is then agitated with air, when a sample taken from the tank
and filtered should give a clear filtrate.

Having obtained this clear solution, agitation is stopped, and the
contents of the tank passed through a filter press. The scum, which
accumulates on the treatment tank, may be transferred to a perforated
box suspended over the tank, and the liquor allowed to drain from it.
The filtered liquor is now rendered slightly alkaline by the addition of
caustic soda or carbonate, and, after filtering, is ready for
evaporation.

The acid and alum salt used in the above treatment must be carefully
examined for the presence of arsenic, and any deliveries of either
article, which contain that impurity, rejected.

Lime, bog ore, and various metallic salts, such as ferric chloride,
barium chloride, and copper sulphate have been suggested, and in some
instances are used instead of aluminium sulphate, but the latter is
generally employed.

_Evaporation to Crude Glycerine._--The clear treated lyes, being now
free from fatty, resinous, and albuminous matter, and consisting
practically of an aqueous solution of common salt (sodium chloride) and
glycerine, is converted into crude glycerine by concentration, which
eliminates the water and causes most of the salt to be deposited.

This concentration was originally performed in open pans heated by fire
or waste combustible gases. In the bottom of each pan was placed a dish
in which the salt deposited, and this dish was lifted out periodically
by the aid of an overhead crane and the contents emptied and washed.
Concentration was continued until the temperature of the liquor was 300°
F. (149° C.), when it was allowed to rest before storing.

This liquor on analysis gave 80 per cent. glycerol and from 9 to 10-1/2
per cent. salts (ash); hence the present standard for crude glycerine.

Concentration in open pans has now been superseded by evaporation _in
vacuo_. The subject of the gradual development of the modern efficient
evaporating plant from the vacuum pan, originated and successfully
applied by Howard in 1813 in the sugar industry, is too lengthy to
detail here, suffice it to say that the multiple effects now in vogue
possess distinct advantages--the greatest of these being increased
efficiency combined with economy.

The present type of evaporator consists of one or more vessels, each
fitted with a steam chamber through which are fixed vertical hollow
tubes. The steam chamber of the first vessel is heated with direct
steam, or with exhaust steam (supplied from the exhaust steam receiver
into which passes the waste steam of the factory); the treated lyes
circulating through the heated tubes is made to boil at a lower
temperature, with the reduced pressure, than is possible by heating in
open pans.

The vapour given off by the boiling liquor is conveyed through large
pipes into the steam chamber of the second vessel, where its latent heat
is utilised in producing evaporation, the pressure being further
reduced, as this second vessel is under a greater vacuum than No. 1.
Thus we get a "double effect," as the plant consisting of two pans is
termed. The vapours discharged from the second vessel during boiling are
passed through pipes to the steam chamber of the third vessel (in a
"triple effect"), and there being condensed, create a partial vacuum in
the second vessel. The third vessel may also be heated by means of live
steam. The vapours arising from the last vessel of the evaporating
plant, or in the case of a "single effect" from the vessel, are conveyed
into a condenser and condensed by injection water, which is drawn off by
means of the pump employed for maintaining a vacuum of 28 inches in the
vessel.

In the most recent designs of large evaporative installations, the
vapours generated from the last vessel are drawn through a device
consisting of a number of tubes enclosed in a casing, and the latent
heat raises the temperature of the treated lyes proceeding through the
tubes to supply the evaporator.

It will thus be observed that the object of multiple effects is to
utilise all the available heat in performing the greatest possible
amount of work. Special devices are attached to the plant for
automatically removing the condensed water from the steam chambers
without the loss of useful heat, and as a precaution against splashing
over and subsequent loss of glycerine through conveyance to the steam
chamber, dash plates and "catch-alls" or "save-alls" of various designs
are fitted on each vessel.

In working the plant, the liquor in each vessel is kept at a fairly
constant level by judicious feeding from one to the other; the first
vessel is, of course, charged with treated lyes. As the liquor acquires
a density of 42° Tw. (25° B.) salt begins to deposit, and may be
withdrawn into one of the many patented appliances, in which it is freed
from glycerine, washed and dried ready for use at the soap pans.
Difficulty is sometimes experienced with the tubes becoming choked with
salt, thereby diminishing and retarding evaporation. It may be necessary
to dissolve the encrusted salt with lyes or water, but with careful
working the difficulty can be obviated by washing out with weak lyes
after each batch of crude glycerine has been run away, or by increasing
the circulation.

It is claimed that by the use of the revolving heater designed by
Lewkowitsch, the salting up of tubes is prevented.

The salt having been precipitated and removed, evaporation is continued
until a sample taken from the last vessel has a density of 60° Tw. (33.3
B.) at 60° F. (15.5° C.). When this point is reached, the crude
glycerine is ready to be withdrawn into a tank, and, after allowing the
excess of salt to deposit, may be transferred to the storage tank.

The colour of crude glycerine varies from light brown to dark brown,
almost black, and depends largely on the materials used for soap-making.
The organic matter present in good crude glycerine is small in amount,
often less than 1 per cent.; arsenic, sulphides and sulphites should be
absent. Crude glycerine is refined in some cases by the producers
themselves; others sell it to firms engaged more particularly in the
refined glycerine trade.

_Distillation._--Crude glycerine is distilled under vacuum with the aid
of superheated steam. The still is heated directly with a coal or coke
fire, and in this fire space is the superheater, which consists of a
coil of pipes through which high pressure steam from the boiler is
superheated.

The distillation is conducted at a temperature of 356°F. (180° C.). To
prevent the deposition and burning of salt on the still-bottom during
the distillation, a false bottom is supported about 1 foot from the base
of the still. With the same object in view, it has been suggested to
rotate the contents with an agitator fixed in the still.

Every care is taken that the still does not become overheated; this
precaution not only prevents loss of glycerine through carbonisation,
but also obviates the production of tarry and other bodies which might
affect the colour, taste, and odour of the distilled glycerine. The
vacuum to be used will, of course, depend upon the heat of the fire and
still, but as a general rule good results are obtained with an 18 inch
vacuum.

There are quite a large number of designs for still heads, and
"catch-alls," having for their object the prevention of loss of
glycerine.

The distillate passes into a row of condensers, to each of which is
attached a receptacle or receiver. It is needless to state that the
condensing capacity should be in excess of theoretical requirements. The
fractions are of varying strengths and quality; that portion, with a
density less than 14° Tw. (19.4° B.), is returned to the treated-lyes
tank. The other portion of the distillate is concentrated by means of a
dry steam coil in a suitable vessel under a 28 inch vacuum.

When sufficiently concentrated the glycerine may be decolorised, if
necessary, by treating with 1 per cent. animal charcoal and passing
through a filter press, from which it issues as "dynamite glycerine".

The residue in the still, consisting of 50-60 per cent. glycerine and
varying proportions of various sodium salts--_e.g._ acetate, chloride,
sulphate, and combinations with non-volatile organic acids--is generally
boiled with water and treated with acid.

The tar, which is separated, floats on the surface as the liquor is
cooling, and may be removed by ladles, or the whole mixed with waste
charcoal, and filtered.

The filtrate is then evaporated, when the volatile organic acids are
driven off; the concentrated liquor is finally mixed with crude
glycerine which is ready for distillation, or it may be distilled
separately.

_Distilled Glycerine._--This class of commercial glycerine, although of
limited use in various other branches of industry, finds its chief
outlet in the manufacture of explosives.

Specifications are usually given in contracts drawn up between buyers
and sellers, to which the product must conform.

The chief stipulation for dynamite glycerine is its behaviour in the
nitration test. When glycerine is gradually added to a cold mixture of
strong nitric and sulphuric acids, it is converted into nitro-glycerine,
which separates as an oily layer on the surface of the acid. The more
definite and rapid the separation, the more suitable is the glycerine
for dynamite-making.

Dynamite glycerine should be free from arsenic, lime, chlorides, and
fatty acids, the inorganic matter should not amount to more than 0.1 per
cent., and a portion diluted and treated with nitrate of silver solution
should give no turbidity or discoloration in ten minutes. The specific
gravity should be 1.262 at 15° C. (59° F.) and the colour somewhat
yellow.

_Chemically pure glycerine_ or double distilled glycerine is produced by
redistilling "once distilled" glycerine. Every care is taken to avoid
all fractions which do not withstand the nitrate of silver test. The
distillation is very carefully performed under strict supervision.

The distillate is concentrated and after treatment with animal charcoal
and filtration should conform to the requirements of the British
Pharmacopoeia. These are specified as follows: Specific gravity at
15.5° C., 1.260. It should yield no characteristic reaction with the
tests for lead, copper, arsenium, iron, calcium, potassium, sodium,
ammonium, chlorides, or sulphates. It should contain no sugars and leave
no residue on burning.

_Animal Charcoal for Decolorisation._--The application of animal
charcoal for decolorising purposes dates back a century, and various are
the views that have been propounded to explain its action. Some
observers base it upon the physical condition of the so-called carbon
present, and no doubt this is an important factor, coupled with the
porosity. Others consider that the nitrogen, which is present in all
animal charcoal and extremely difficult to remove, is essential to the
action. Animal charcoal should be freed from gypsum (sulphate of lime),
lest in the burning, sulphur compounds be formed which would pass into
the glycerine and contaminate it.

The "char" should be well boiled with water, then carbonate of soda or
caustic soda added in sufficient quantity to give an alkaline reaction,
and again well boiled. The liquor is withdrawn and the charcoal washed
until the washings are no longer alkaline. The charcoal is then
separated from the liquor and treated with hydrochloric acid; opinions
differ as to the amount of acid to be used. Some contend that phosphate
of lime plays such an important part in decolorising that it should not
be removed, but it has, however, been demonstrated that this substance
after exposure to heat has very little decolorising power.

Animal charcoal boiled with four times its weight of a mixture
consisting of equal parts of commercial hydrochloric acid (free from
arsenic) and water for twelve hours, then washed free from acid, dried,
and burned in closed vessels gives a product possessed of great
decolorising power for use with glycerines.

A good animal charcoal will have a dull appearance, and be of a deep
colour; it should be used in fine grains and not in the form of a
powder.

The charcoal from the filter presses is washed free from glycerine
(which is returned to the treated lyes), cleansed from foreign
substances by the above treatment and revivified by carefully heating in
closed vessels for twelve hours.

_Glycerine obtained by other Methods of Saponification._--French
saponification or "candle crude" glycerine is the result of
concentration of "sweet water" produced in the manufacture of stearine
and by the autoclave process. It contains 85-90 per cent. glycerol,
possesses a specific gravity of 1.240-1.242, and may be readily
distinguished from the soap-crude glycerine by the absence of salt
(sodium chloride). This glycerine is easily refined by treatment with
charcoal.

The glycerine water resulting from acid saponification methods requires
to be rendered alkaline by the addition of lime--the sludge is
separated, and the liquor evaporated to crude. The concentration may be
performed in two stages--first to a density of 32° Tw. (20° B.), when
the calcium sulphate is allowed to deposit, and the separated liquor
concentrated to 48° Tw. (28° B.) glycerine, testing 85 per cent.
glycerol and upwards.

_Yield of Glycerine from Fats and Oils._--The following represent
practicable results which should be obtained from the various
materials:--

    Tallow                 9 per cent. of 80 per cent. Glycerol.
    Cotton-seed oil       10    "
    Cocoa-nut oil         12    "
    Palm-kernel oil       18    "
    Olive oil             10    "
    Palm oil               6    "
    Greases (Bone fats)  6-8    "

The materials vary in glycerol content with the methods of preparation;
especially is this the case with tallows and greases.

Every care should be taken that the raw materials are fresh and they
should be carefully examined to ascertain if any decomposition has taken
place in the glycerides--this would be denoted by the presence of an
excess of free acidity, and the amount of glycerol obtainable from such
a fat would be correspondingly reduced.



CHAPTER X.

ANALYSIS OF RAW MATERIALS, SOAP, AND GLYCERINE.

     _Fats and Oils--Alkalies and Alkali Salts--Essential
     Oils--Soap--Lyes--Crude Glycerine._


_Raw Materials._--Average figures have already been given in Chapters
III. and VIII. for the more important physical and chemical
characteristics of fats and oils, also of essential oils; the following
is an outline of the processes usually adopted in their determination.
For fuller details, text-books dealing exhaustively with the respective
subjects should be consulted.


FATS AND OILS.

It is very undesirable that any of these materials should be allowed to
enter the soap pan without an analysis having first been made, as the
oil may not only have become partially hydrolysed, involving a loss of
glycerine, or contain albuminous matter rendering the soap liable to
develop rancidity, but actual sophistication may have taken place. Thus
a sample of tallow recently examined by the authors contained as much as
40 per cent. of an unsaponifiable wax, which would have led to disaster
in the soap pan, had the bulk been used without examination. After
observing the appearance, colour, and odour of the sample, noting any
characteristic feature, the following physical and chemical data should
be determined.

_Specific Gravity at 15° C._ This may be taken by means of a Westphal
balance, or by using a picnometer of either the ordinary gravity bottle
shape, with perforated stopper, or the Sprengel U-tube. The picnometer
should be calibrated with distilled water at 15° C. The specific gravity
of solid fats may be taken at an elevated temperature, preferably that
of a boiling water bath.

_Free acidity_ is estimated by weighing out from 2 to 5 grammes of the
fat or oil, dissolving in neutral alcohol (purified methylated spirit)
with gentle heat, and titrating with a standard aqueous or alcoholic
solution of caustic soda or potash, using phenol-phthalein as indicator.

The contents of the flask are well shaken after each addition of alkali,
and the reaction is complete when the slight excess of alkali causes a
permanent pink coloration with the indicator. The standard alkali may be
N/2, N/5, or N/10.

It is usual to calculate the result in terms of oleic acid (1 c.c. N/10
alkali = 0.0282 gramme oleic acid), and express in percentage on the fat
or oil.

_Example._--1.8976 grammes were taken, and required 5.2 c.c. of N/10 KOH
solution for neutralisation.

          5.2 × 0.0282 × 100
          ------------------ = 7.72 per cent. free fatty acids,
                1.8976                expressed as oleic acid.

The free acidity is sometimes expressed as _acid value_, which is the
amount of KOH in milligrammes necessary to neutralise the free acid in 1
gramme of fat or oil.

In the above example:--

          5.2 × 5.61
          ---------- = 15.3 acid value.
            1.8976

The _saponification equivalent_ is determined by weighing 2-4 grammes of
fat or oil into a wide-necked flask (about 250 c.c. capacity), adding 30
c.c. neutral alcohol, and warming under a reflux condenser on a steam or
water-bath. When boiling, the flask is disconnected, 50 c.c. of an
approximately semi-normal alcoholic potash solution carefully added from
a burette, together with a few drops of phenol-phthalein solution, and
the boiling under a reflux condenser continued, with frequent agitation,
until saponification is complete (usually from 30-60 minutes) which is
indicated by the absence of fatty globules. The excess of alkali is
titrated with N/1 hydrochloric or sulphuric acid.

The value of the approximately N/2 alkali solution is ascertained by
taking 50 c.c. together with 30 c.c. neutral alcohol in a similar flask,
boiling for the same length of time as the fat, and titrating with N/1
hydrochloric or sulphuric acid. The "saponification equivalent" is the
amount of fat or oil in grammes saponified by 1 equivalent or 56.1
grammes of caustic potash.

_Example._--1.8976 grammes fat required 18.95 c.c. N/1 acid to
neutralise the unabsorbed alkali.

Fifty c.c. approximately N/2 alcoholic potash solution required 25.6
c.c. N/ acid..

          25.6 - 18.95 = 6.65 c.c. N/1 KOH required by fat.

          1.8976 × 1000 / 6.65 = 285.3 Saponification Equivalent.

The result of this test is often expressed as the "Saponification
Value," which is the number of milligrammes of KOH required for the
saponification of 1 gramme of fat. This may be found by dividing 56,100
by the saponification equivalent or by multiplying the number of c.c. of
N/1 alkali absorbed, by 56.1 and dividing by the quantity of fat taken.
Thus, in the above example:--

          6.65 × 56.1 / 1.8976 = 196.6 Saponification Value.

The _ester_ or _ether value_, or number of milligrammes of KOH required
for the saponification of the neutral esters or glycerides in 1 gramme
of fat, is represented by the difference between the saponification and
acid values. In the example given, the ester value would be 196.6 - 15.3
= 181.3.

_Unsaponifiable Matter._--The usual method adopted is to saponify about
5 grammes of the fat or oil with 50 c.c. of approximately N/2 alcoholic
potash solution by boiling under a reflux condenser with frequent
agitation for about 1 hour. The solution is then evaporated to dryness
in a porcelain basin over a steam or water-bath, and the resultant soap
dissolved in about 200 c.c. hot water. When sufficiently cool, the soap
solution is transferred to a separating funnel, 50 c.c. of ether added,
the whole well shaken, and allowed to rest. The ethereal layer is
removed to another separator, more ether being added to the aqueous soap
solution, and again separated. The two ethereal extracts are then washed
with water to deprive them of any soap, separated, transferred to a
flask, and the ether distilled off upon a water-bath. The residue, dried
in the oven at 100° C. until constant, is the "unsaponifiable matter,"
which is calculated to per cent. on the oil.

In this method, it is very frequently most difficult to obtain a
distinct separation of ether and aqueous soap solution--an intermediate
layer of emulsion remaining even after prolonged standing, and various
expedients have been recommended to overcome this, such as addition of
alcohol (when petroleum ether is used), glycerine, more ether, water, or
caustic potash solution, or by rotatory agitation.

A better plan is to proceed as in the method above described as far as
dissolving the resulting soap in 200 c.c. water, and then boil for
twenty or thirty minutes. Slightly cool and acidify with dilute
sulphuric acid (1 to 3), boil until the fatty acids are clear, wash with
hot water free from mineral acid, and dry by filtering through a hot
water funnel.

Two grammes of the fatty acids are now dissolved in neutral alcohol
saturated with some solvent, preferably a light fraction of benzoline, a
quantity of the solvent added to take up the unsaponifiable matter, and
the whole boiled under a reflux condenser. After cooling, the liquid is
titrated with N/2 aqueous KOH solution, using phenol-phthalein as
indicator, this figure giving the amount of the total fatty acids
present. The whole is then poured into a separating funnel, when
separation immediately takes place. The alcoholic layer is withdrawn,
the benzoline washed with warm water (about 32° C.) followed by neutral
alcohol (previously saturated with the solvent), and transferred to a
tared flask, which is attached to a condenser, and the benzoline
distilled off. The last traces of solvent remaining in the flask are
removed by gently warming in the water-oven, and the flask cooled and
weighed, thus giving the amount of unsaponifiable matter.

_Constitution of the Unsaponifiable Matter._--Unsaponifiable matter may
consist of cholesterol, phytosterol, solid alcohols (cetyl and ceryl
alcohols), or hydrocarbons (mineral oil). Cholesterol is frequently
found in animal fats, and phytosterol is a very similar substance
present in vegetable fats. Solid alcohols occur naturally in sperm oil,
but hydrocarbons, which may be generally recognised by the fluorescence
or bloom they give to the oil, are not natural constituents of animal or
vegetable oils and fats.

The presence of cholesterol and phytosterol may be detected by
dissolving a small portion of the unsaponifiable matter in acetic
anhydride, and adding a drop of the solution to one drop of 50 per cent.
sulphuric acid on a spot plate, when a characteristic blood red to
violet coloration is produced. It has been proposed to differentiate
between cholesterol and phytosterol by their melting points, but it is
more reliable to compare the crystalline forms, the former crystallising
in laminæ, while the latter forms groups of needle-shaped tufts. Another
method is to convert the substance into acetate, and take its melting
point, cholesterol acetate melting at 114.3-114.8° C., and phytosterol
acetate at 125.6°-137° C.

Additional tests for cholesterol have been recently proposed by
Lifschütz (_Ber. Deut. Chem. Ges._, 1908, 252-255), and Golodetz (_Chem.
Zeit._, 1908, 160). In that due to the former, which depends on the
oxidation of cholesterol to oxycholesterol ester and oxycholesterol, a
few milligrammes of the substance are dissolved in 2-3 c.c. glacial
acetic acid, a little benzoyl peroxide added, and the solution boiled,
after which four drops of strong sulphuric acid are added, when a
violet-blue or green colour is produced, if cholesterol is present, the
violet colour being due to oxycholesterol ester, the green to
oxycholesterol. Two tests are suggested by Golodetz (1) the addition of
one or two drops of a reagent consisting of five parts of concentrated
sulphuric acid and three parts of formaldehyde solution, which colours
cholesterol a blackish-brown, and (2) the addition of one drop of 30 per
cent. formaldehyde solution to a solution of the substance in
trichloracetic acid, when with cholesterol an intense blue coloration is
produced.

_Water._--From 5 to 20 grammes of the fat or oil are weighed into a
tared porcelain or platinum dish, and stirred with a thermometer, whilst
being heated over a gas flame at 100° C. until bubbling or cracking has
ceased, and reweighed, the loss in weight representing the water. In
cases of spurting a little added alcohol will carry the water off
quietly.

To prevent loss by spurting, Davis (_J. Amer. Chem. Soc._, 23, 487) has
suggested that the fat or oil should be added to a previously dried and
tared coil of filter paper contained in a stoppered weighing bottle,
which is then placed in the oven and dried at 100° C. until constant in
weight. Of course, this method is not applicable to oils or fats liable
to oxidation on heating.

_Dregs, Dirt, Adipose Tissue, Fibre, etc._--From 10 to 15 grammes of the
fat are dissolved in petroleum ether with frequent stirring, and passed
through a tared filter paper. The residue retained by the filter paper
is washed with petroleum ether until free from fat, dried in the
water-oven at 100° C. and weighed.

If the amount of residue is large, it may be ignited, and the proportion
and nature of the ash determined.

The amount of impurities may also be estimated by Tate's method, which
is performed by weighing 5 grammes of fat into a separating funnel,
dissolving in ether, and allowing the whole to stand to enable the water
to deposit. After six hours' rest the water is withdrawn, the tube of
the separator carefully dried, and the ethereal solution filtered
through a dried tared filter paper into a tared flask. Well wash the
filter with ether, and carefully dry at 100° C. The ether in the flask
is recovered, and the flask dried until all ether is expelled, and its
weight is constant. The amount of fat in the flask gives the quantity of
actual fat in the sample taken; the loss represents the water and other
impurities, and these latter may be obtained from the increase of weight
of the filter paper.

_Starch_ may be detected by the blue coloration it gives with iodine
solution, and confirmed by microscopical examination, or it may be
converted into glucose by inversion, and the glucose estimated by means
of Fehling's solution.

_Iodine Absorption._--This determination shows the amount of iodine
absorbed by a fat or oil, and was devised by Hübl, the reagents required
being as follows:--

(1) Solution of 25 grammes iodine in 500 c.c. absolute alcohol; (2)
solution of 30 grammes mercuric chloride in 500 c.c. absolute alcohol,
these two solutions being mixed together and allowed to stand at least
twelve hours before use; (3) a freshly prepared 10 per cent. aqueous
solution of potassium iodide; and (4) a N/10 solution of sodium
thiosulphate, standardised just prior to use by titrating a weighed
quantity of resublimed iodine dissolved in potassium iodide solution.

In the actual determination, 0.2 to 0.5 gramme of fat or fatty acids is
carefully weighed into a well-fitting stoppered 250 c.c. bottle,
dissolved in 10 c.c. chloroform, and 25 c.c. of the Hübl reagent added,
the stopper being then moistened with potassium iodide solution and
placed firmly in the bottle, which is allowed to stand at rest in a dark
place for four hours. A blank experiment is also performed, using the
same quantities of chloroform and Hübl reagent, and allowing to stand
for the same length of time.

After the expiration of four hours 20 c.c. of 10 per cent. solution of
potassium iodide and 150 c.c. water are added to the contents of the
bottle, and the excess of iodine titrated with N/10 sodium thiosulphate
solution, the whole being well agitated during the titration, which is
finished with starch paste as indicator. The blank experiment is
titrated in the same manner, and from the amount of thiosulphate
required in the blank experiment is deducted the number of c.c. required
by the unabsorbed iodine in the other bottle; this figure multiplied by
the iodine equivalent of 1 c.c. of the thiosulphate solution and by 100,
dividing the product by the weight of fat taken, gives the "Iodine
Number".

_Example._--1 c.c. of the N/10 sodium thiosulphate solution is found
equal to 0.0126 gramme iodine.

0.3187 gramme of fat taken. Blank requires 48.5 c.c. thiosulphate.

Bottle containing oil requires 40.0 c.c. thiosulphate.

48.5 - 40.0 = 8.5, and the iodine absorption of the fat is--

          8.5 × 0.0126 × 100
          ------------------ = 33.6.
                0.3187

Wijs showed that by the employment of a solution of iodine monochloride
in glacial acetic acid reliable iodine figures are obtained in a much
shorter time, thirty minutes being sufficient, and this method is now in
much more general use than the Hübl. Wijs' iodine reagent is made by
dissolving 13 grammes iodine in 1 litre of glacial acetic acid and
passing chlorine into the solution until the iodine is all converted
into iodine monochloride. The process is carried out in exactly the same
way as with the Hübl solution except that the fat is preferably
dissolved in carbon tetrachloride instead of in chloroform.

_Bromine absorption_ has now been almost entirely superseded by the
iodine absorption, although there are several good methods. The
gravimetric method of Hehner (_Analyst_, 1895, 49) was employed by one
of us for many years with very good results, whilst the bromine-thermal
test of Hehner and Mitchell (_Analyst_, 1895, 146) gives rapid and
satisfactory results. More recently MacIlhiney (_Jour. Amer. Chem.
Soc._, 1899, 1084-1089) drew attention to bromine absorption methods and
tried to rewaken interest in them.

The _Refractive index_ is sometimes useful for discriminating between
various oils and fats, and, in conjunction with other physical and
chemical data, affords another means of detecting adulteration.

Where a great number of samples have to be tested expeditiously, the
Abbé refractometer or the Zeiss butyro-refractometer may be recommended
on account of the ease with which they are manipulated. The most usual
temperature of observations is 60° C.

The _Titre_ or setting point of the fatty acids was devised by Dalican,
and is generally accepted in the commercial valuation of solid fats as a
gauge of firmness, and in the case of tallow has a considerable bearing
on the market value.

One ounce of the fat is melted in a shallow porcelain dish, and 30 c.c.
of a 25 per cent. caustic soda solution added, together with 50 c.c. of
redistilled methylated spirit. The whole is stirred down on the water
bath until a pasty soap is obtained, when another 50 c.c. of methylated
spirit is added, which redissolves the soap, and the whole again stirred
down to a solid soap. This is then dissolved in distilled water, a
slight excess of dilute sulphuric acid added to liberate the fatty
acids, and the whole warmed until the fatty acids form a clear liquid
on the surface. The water beneath the fatty acids is then syphoned off,
more distilled water added to wash out any trace of mineral acid
remaining, and again syphoned off, this process being repeated until the
washings are no longer acid to litmus paper, when the fatty acids are
poured on to a dry filter paper, which is inserted in a funnel resting
on a beaker, and the latter placed on the water-bath, where it is left
until the clear fatty acids have filtered through.

About 10-15 grammes of the pure fatty acids are now transferred to a
test tube, 6" × 1", warmed until molten, and the tube introduced through
a hole in the cork into a flask or wide-mouthed bottle. A very accurate
thermometer, graduated into fifths of a degree Centigrade (previously
standardised), is immersed in the fatty acids, so that the bulb is as
near the centre as possible, and when the fatty acids just begin to
solidify at the bottom of the tube, the thermometer is stirred round
slowly. The mercury will descend, and stirring is continued until it
ceases to fall further, at which point the thermometer is very carefully
observed. It will be found that the temperature will rise rapidly and
finally remain stationary for a short time, after which it will again
begin to drop until the temperature of the room is reached. The maximum
point to which the temperature rises is known as the "titre" of the
sample.


ALKALIES AND ALKALI SALTS.

Care should be bestowed upon the sampling of solid caustic soda or
potash as the impurities during the solidification always accumulate in
the centre of the drum, and an excess of that portion must be avoided or
the sample will not be sufficiently representative. The sampling should
be performed expeditiously to prevent carbonating, and portions placed
in a stoppered bottle. The whole should be slightly broken in a mortar,
and bright crystalline portions taken for analysis, using a stoppered
weighing bottle.

_Caustic Soda and Caustic Potash._--These substances are valued
according to the alkali present in the form of caustic (hydrate) and
carbonate.

About 2 grammes of the sample are dissolved in 50 c.c. distilled water,
and titrated with N/1 sulphuric acid, using phenol-phthalein as
indicator, the alkalinity so obtained representing all the caustic
alkali and one-half the carbonate, which latter is converted into
bicarbonate. One c.c. N/1 acid = 0.031 gramme Na_{2}O or 0.040 gramme
NaOH and 0.047 gramme K_{2}O, or 0.056 gramme KOH.

After this first titration, the second half of the carbonate may be
determined in one of two ways, either:--

(1) By adding from 3-5 c.c. of N/10 acid, and well boiling for five
minutes to expel carbonic-acid gas, after which the excess of acid is
titrated with N/10 soda solution; or

(2) After adding two drops of methyl orange solution, N/10 acid is run
in until the solution acquires a faint pink tint.

In the calculation of the caustic alkali, the number of c.c. of acid
required in the second titration, divided by 10, is subtracted from that
used in the first, and this difference multiplied by 0.031, or 0.047
gives the amount of Na_{2}O or K_{2}O respectively in the weight of
sample taken, whence the percentage may be readily calculated.

The proportion of carbonate is calculated by multiplying the amount of
N/10 acid required in the second titration by 2, and then by either
0.0031 or 0.0047 to give the amount of carbonate present, expressed as
Na_{2}O or K_{2}O respectively.

An alternative method is to determine the alkalinity before and after
the elimination of carbonate by chloride of barium.

About 7-8 grammes of the sample are dissolved in water, and made up to
100 c.c., and the total alkalinity determined by titrating 20 c.c. with
N/1 acid, using methyl orange as indicator. To another 20 c.c. is added
barium chloride solution (10 per cent.) until it ceases to give a
precipitate, the precipitate allowed to settle, and the clear
supernatant liquid decanted off, the precipitate transferred to a filter
paper and well washed, and the filtrate titrated with N/1 acid, using
phenol-phthalein as indicator. The second titration gives the amount of
caustic alkali present, and the difference between the two the
proportion of carbonate.

When methyl orange solution is used as indicator, titrations must be
carried out cold.

Reference has already been made (p. 39) to the manner in which the
alkali percentage is expressed in English degrees in the case of caustic
soda.

_Chlorides_ are estimated by titrating the neutral solution with N/10
silver nitrate solution, potassium chromate being used as indicator. One
c.c. N/10 AgNO_{3} solution = 0.00585 gramme sodium chloride.

The amount of acid necessary for exact neutralisation having already
been ascertained, it is recommended to use the equivalent quantity of
N/10 nitric acid to produce the neutral solution.

_Sulphides_ may be tested for, qualitatively, with lead acetate
solution.

_Aluminates_ are determined gravimetrically in the usual manner; 2
grammes are dissolved in water, rendered acid with HCl, excess of
ammonia added, and the gelatinous precipitate of aluminium hydrate
collected on a filter paper, washed, burnt, and weighed.

       *       *       *       *       *

_Carbonated Alkali (Soda Ash)._--The total or available alkali is, of
course, the chief factor to be ascertained, and for this purpose it is
convenient to weigh out 3.1 grammes of the sample, dissolve in 50 c.c.
water, and titrate with N/1 sulphuric or hydrochloric acid, using methyl
orange as indicator. Each c.c. of N/1 acid required represents 1 per
cent. Na_{2}O in the sample under examination.

A more complete analysis of soda ash would comprise:--

_Insoluble matter_, remaining after 10 grammes are dissolved in warm
water. This is washed on to a filter-paper, dried, ignited, and weighed.

The filtrate is made up to 200 c.c., and in it may be determined:--

_Caustic soda_, by titrating with N/1 acid the filtrate resulting from
the treatment of 20 c.c. (equal to 1 gramme) with barium chloride
solution.

_Carbonate._--Titrate 20 c.c. with N/1 acid, and deduct the amount of
acid required for the Caustic.

_Chlorides._--Twenty c.c. are exactly neutralised with nitric acid,
titrated with N/10 AgNO_{3} solution, using potassium chromate as
indicator.

_Sulphates._--Twenty c.c. are acidulated with HCl, and the sulphates
precipitated with barium chloride; the precipitate is collected on a
filter paper, washed, dried, ignited, and weighed, the result being
calculated to Na_{2}SO_{4}.

_Sulphides and Sulphites._--The presence of these compounds is denoted
by the evolution of sulphuretted hydrogen and sulphurous acid
respectively when the sample is acidulated. Sulphides may also be tested
for, qualitatively, with lead acetate solution, or test-paper of sodium
nitro-prusside.

The total quantity of these compounds may be ascertained by acidulating
with acetic acid, and titrating with N/10 iodine solution, using starch
paste as indicator. One c.c. N/10 iodine solution = 0.0063 gramme
Na_{2}SO_{3}.

The amount of sulphides may be estimated by titrating the hot soda
solution, to which ammonia has been added, with an ammoniacal silver
nitrate solution, 1 c.c. of which corresponds to 0.005 gramme Na_{2}S.
As the titration proceeds, the precipitate is filtered off, and the
addition of ammoniacal silver solution to the filtrate continued until a
drop produces only a slight opacity. The presence of chloride, sulphate,
hydrate, or carbonate does not interfere with the accuracy of this
method. The ammoniacal silver nitrate solution is prepared by dissolving
13.345 grammes of pure silver in pure nitric acid, adding 250 c.c.
liquor ammoniæ fortis, and diluting to 1 litre.

_Carbonate of Potash (Pearl Ash)._--The total or available alkali may be
estimated by taking 6.9 grammes of the sample, and titrating with N/1
acid directly, or adding 100 c.c. N/1 sulphuric acid, boiling for a few
minutes, and titrating the excess of acid with N/1 caustic soda
solution, using litmus as indicator. In this case each c.c. N/1 acid
required, is equivalent, in the absence of Na_{2}CO_{3}, to 1 per cent.
K_{2}CO_{3}.

Carbonate of potash may be further examined for the following:--

_Moisture._--From 2-3 grammes are heated for thirty minutes in a
crucible over a gas flame, and weighed when cold, the loss in weight
representing the moisture.

_Insoluble residue_, remaining after solution in water, filtering and
well washing.

_Potassium_ may be determined by precipitation as potassium
platino-chloride thus:--Dissolve 0.5 gramme in a small quantity (say 10
c.c.) of water, and carefully acidulate with hydrochloric acid,
evaporate the resultant liquor to dryness in a tared platinum basin, and
heat the residue gradually to dull redness. Cool in a desicator, weigh,
and express the result as "mixed chlorides," _i.e._ chlorides of soda
and potash. To the mixed chlorides add 10 c.c. water, and platinic
chloride in excess (the quantity may be three times the amount of the
mixed chlorides) and evaporate nearly to dryness; add 15 c.c. alcohol
and allow to stand three hours covered with a watch-glass, giving the
dish a gentle rotatory movement occasionally. The clear liquid is
decanted through a tared filter, and the precipitate well washed with
alcohol by decantation, and finally transferred to the filter, dried and
weighed. From the weight of potassium platino-chloride, K_{2}PtCl_{6},
is calculated the amount of potassium oxide K_{2}O by the use of the
factor 94/488.2 or 0.19254.

_Chlorides_, determined with N/10 silver nitrate solution, and
calculated to KCl.

_Sulphates_, estimated as barium sulphate, and calculated to
K_{2}SO_{4}.

_Sodium Carbonate_, found by deducting the K_{2}CO_{3} corresponding to
the actual potassium as determined above, from the total alkali.

_Iron_, precipitated with excess of ammonia, filtered, ignited, and
weighed as Fe_{2}O_{3}.


SODIUM CHLORIDE (COMMON SALT).

This should be examined for the following:--

_Actual Chloride_, either titrated with N/10 silver nitrate solution,
using neutral potassium chromate solution as indicator, or, preferably,
estimated gravimetrically as silver chloride by precipitation with
silver nitrate solution, the precipitate transferred to a tared filter
paper, washed, dried and weighed.

_Insoluble matter_, remaining on dissolving 5 grammes in water, and
filtering. This is washed, dried, ignited and weighed.

_Moisture._--5 grammes are weighed into a platinum crucible, and heat
gently applied. The temperature is gradually increased to a dull red
heat, which is maintained for a few minutes, the dish cooled in a
desicator, and weighed.

_Sulphates_ are estimated by precipitation as barium sulphate and
calculated to Na_{2}SO_{4}.

_Sodium._--This may be determined by converting the salt into sodium
sulphate by the action of concentrated sulphuric acid, igniting to drive
off hydrochloric and sulphuric acids, and fusing the mass until constant
in weight, weighing finally as Na_{2}SO_{4}.


POTASSIUM CHLORIDE.

This should be examined, in the same way as sodium chloride, for
chloride, insoluble matter, moisture, and sulphate. The potassium may be
determined as potassium platino-chloride, as described under carbonate
of potash.


SILICATES OF SODA AND POTASH.

The most important determinations for these are total alkali and silica.

_Total alkali_ is estimated by dissolving 2 grammes in distilled water,
and titrating when cold, with N/1 acid, using methyl orange as
indicator.

_Silica_ may be determined by dissolving 1 gramme in distilled water,
rendering the solution acid with HCl, and evaporating to complete
dryness on the water-bath, after which the residue is moistened with HCl
and again evaporated, this operation being repeated a third time. The
residue is then heated to about 150° C., extracted with hot dilute HCl,
filtered, thoroughly washed, dried, ignited in a tared platinum
crucible, and weighed as SiO_{2}.


ESSENTIAL OILS.

As already stated, these are very liable to adulteration, and an
examination of all kinds of oil is desirable, while in the case of the
more expensive varieties it should never be omitted.

_Specific Gravity._--As with fats and oils, this is usually taken at 15°
C., and compared with water at the same temperature. In the case of otto
of rose and guaiac wood oil, however, which are solid at this
temperature, it is generally observed at 30° C. compared with water at
15° C.

The specific gravity is preferably taken in a bottle or U-tube, but if
sufficient of the oil is available and a high degree of accuracy is not
necessary, it may be taken either with a Westphal balance, or by means
of a hydrometer.

_Optical Rotation._--For this purpose a special instrument, known as a
polarimeter, is required, details of the construction and use of which
would be out of place here. Suffice it to mention that temperature plays
an important part in the determination of the optical activity of
certain essential oils, notably in the case of lemon and orange oils.
For these Gildemeister and Hoffmann give the following corrections:--

Lemon oil, below 20° C. subtract 9' for each degree below, above 20° C.
add 8' for each degree above.

Orange oil, below 20° C. subtract 14' for each degree below, above 20°
C. add 13' for each degree above.

_Refractive Index._--This figure is occasionally useful, and is best
determined with an Abbé refractometer, at 20° C.

_Solubility in Alcohol._--This is found by running alcohol of the
requisite strength from a burette into a measured volume of the oil with
constant agitation, until the oil forms a clear solution with the
alcohol. Having noted the quantity of alcohol added, it is well to run
in a small further quantity of alcohol, and observe whether any
opalescence or cloudiness appears.

_Acid_, _ester_, and _saponification values_ are determined exactly as
described under fats and oils. Instead of expressing the result as
saponification value or number, the percentage of ester, calculated in
the form of the most important ester present, may be obtained by
multiplying the number of c.c. of N/1 alkali absorbed in the
saponification by the molecular weight of the ester. Thus, to find the
percentage as linalyl acetate, the number of c.c. absorbed would be
multiplied by 0.196 and by 100, and divided by the weight of oil taken.

_Alcohols._--For the estimation of these, if the oil contains much ester
it must first be saponified with alcoholic potash, to liberate the
combined alcohols, and after neutralising the excess of alkali with
acid, the oil is washed into a separating funnel with water, separated,
dried with anhydrous sodium sulphate, and is then ready for the alcohol
determination.

If there is only a small quantity of ester present, this preliminary
saponification is unnecessary.

The alcohols are estimated by conversion into their acetic esters, which
are then saponified with standard alcoholic potash, thereby furnishing a
measure of the amount of alcohol esterified.

Ten c.c. of the oil is placed in a flask with an equal volume of acetic
anhydride, and 2 grammes of anhydrous sodium acetate, and gently boiled
for an hour to an hour and a half. After cooling, water is added, and
the contents of the flask heated on the water-bath for fifteen to thirty
minutes, after which they are cooled, transferred to a separating
funnel, and washed with a brine solution until the washings cease to
give an acid reaction with litmus paper. The oil is now dried with
anhydrous sodium sulphate, filtered, and 1-2 grammes weighed into a
flask and saponified with alcoholic potash as in the determination of
ester or saponification value.

The calculation is a little complicated, but an example may perhaps
serve to make it clear.

A geranium oil containing 26.9 per cent. of ester, calculated as geranyl
tiglate, was acetylated, after saponification, to liberate the combined
geraniol, and 2.3825 grammes of the acetylated oil required 9.1 c.c. of
N/1 alkali for its saponification.

Now every 196 grammes of geranyl acetate present in the acetylated oil
correspond to 154 grammes of geraniol, so that for every 196 grammes of
ester now present in the oil, 42 grammes have been added to its weight,
and it is therefore necessary to make a deduction from the weight of oil
taken for the final saponification to allow for this, and since each
c.c. of N/1 alkali absorbed corresponds to 0.196 gramme of geranyl
acetate, the amount to be deducted is found by multiplying the number of
c.c. absorbed by 0.042 gramme, the formula for the estimation of total
alcohols thus becoming in the example given:--

                                    9.1 × 0.154 × 100
          Per cent. of geraniol = ---------------------- = 70.2
                                  2.3825 - (9.1 × 0.042)

The percentage of combined alcohols can be calculated from the amount of
ester found, and by subtracting this from the percentage of total
alcohols, that of the free alcohols is obtained.

In the example quoted, the ester corresponds to 17.6 per cent. geraniol,
and this, deducted from the total alcohols, gives 52.6 per cent. free
alcohols, calculated as geraniol.

This process gives accurate results with geraniol, borneol, and menthol,
but with linalol and terpineol the figures obtained are only
comparative, a considerable quantity of these alcohols being decomposed
during the acetylation. The aldehyde citronellal is converted by acetic
anhydride into isopulegol acetate, so that this is also included in the
determination of graniol in citronella oil.

_Phenols._--These bodies are soluble in alkalies, and may be estimated
by measuring 5 c.c. or 10 c.c. of the oil into a Hirschsohn flask (a
flask of about 100 c.c. capacity with a long narrow neck holding 10
c.c., graduated in tenths of a c.c.), adding 25 c.c. of a 5 per cent.
aqueous caustic potash solution, and warming in the water-bath, then
adding another 25 c.c., and after one hour in the water-bath filling the
flask with the potash solution until the unabsorbed oil rises into the
neck of the flask, the volume of this oil being read off when it has
cooled down to the temperature of the laboratory. From the volume of oil
dissolved the percentage of phenols is readily calculated.

_Aldehydes._--In the estimation of these substances, use is made of
their property of combining with sodium bisulphite to form compounds
soluble in hot water. From 5-10 c.c. of the oil is measured into a
Hirschsohn flask, about 30 c.c. of a hot saturated solution of sodium
bisulphite added, and the flask immersed in a boiling water bath, and
thoroughly shaken at frequent intervals. Further quantities of the
bisulphite solution are gradually added, until, after about one hour,
the unabsorbed oil rises into the neck of the flask, where, after
cooling, its volume is read off, and the percentage of absorbed oil, or
aldehydes, calculated.

In the case of lemon oil, where the proportion of aldehydes, though of
great importance, is relatively very small, it is necessary to first
concentrate the aldehydes before determining them. For this purpose, 100
c.c. of the oil is placed in a Ladenburg fractional distillation flask,
and 90 c.c. distilled off under a pressure of not more than 40 mm., and
the residue steam distilled. The oil so obtained is separated from the
condensed water, measured, dried, and 5 c.c. assayed for aldehydes
either by the process already described, or by the following process
devised by Burgess (_Analyst_, 1904, 78):--

Five c.c. of the oil are placed in the Hirschsohn flask, about 20 c.c.
of a saturated solution of neutral sodium sulphite added, together with
a few drops of rosolic acid solution as indicator, and the flask placed
in a boiling water-bath and continually agitated. The contents of the
flask soon become red owing to the liberation of free alkali by the
combination of the aldehyde with part of the sodium sulphite, and this
coloration is just discharged by the addition of sufficient 10 per
cent. acetic-acid solution. The flask is again placed in the water-bath,
the shaking continued, and any further alkali liberated neutralised by
more acetic acid, the process being continued in this way until no
further red colour is produced. The flask is then filled with the sodium
sulphite solution, the volume of the cooled unabsorbed oil read off, and
the percentage of aldehydes calculated as before.

_Solidifying Point, or Congealing Point._--This is of some importance in
the examination of anise and fennel oils, and is also useful in the
examination of otto of rose. A suitable apparatus may be made by
obtaining three test tubes, of different sizes, which will fit one
inside the other, and fixing them together in this way through corks.
The innermost tube is then filled with the oil, and a sensitive
thermometer, similar to that described under the Titre test for fats,
suspended with its bulb completely immersed in the oil. With anise and
fennel, the oil is cooled down with constant stirring until it just
starts crystallising, when the stirring is interrupted, and the maximum
temperature to which the mercury rises noted. This is the solidifying
point.

In the case of otto of rose, the otto is continually stirred, and the
point at which the first crystal is observed is usually regarded as the
congealing point.

_Melting Point._--This is best determined by melting some of the solid
oil, or crystals, and sucking a small quantity up into a capillary tube,
which is then attached by a rubber band to the bulb of the thermometer,
immersed in a suitable bath (water, glycerine, oil, etc.) and the
temperature of the bath gradually raised until the substance in the tube
is sufficiently melted to rise to the surface, the temperature at which
this takes place being the melting point.

The melting point of otto of rose is usually taken in a similar tube to
the setting point, and is considered to be the point at which the last
crystal disappears.

_Iodine Absorption._--In the authors' opinion, this is of some value in
conjunction with other data in judging of the purity of otto of rose. It
is determined by Hübl's process as described under Fats and Oils, except
that only 0.1 to 0.2 gramme is taken, and instead of 10 c.c. of
chloroform, 10 c.c. of pure alcohol are added. The rest of the process
is identical.


SOAP.

In the analysis of soap, it is a matter of considerable importance that
all the determinations should be made on a uniform and average sample of
the soap, otherwise very misleading and unreliable figures are obtained.
Soap very rapidly loses its moisture on the surface, while the interior
of the bar or cake may be comparatively moist, and the best way is to
carefully remove the outer edges and take the portions for analysis from
the centre. In the case of a household or unmilled toilet soap, it is
imperative that the quantities for analysis should all be weighed out as
quickly after each other as possible.

_Fatty Acids._--Five grammes of the soap are rapidly weighed into a
small beaker, distilled water added, and the beaker heated on the water
bath until the soap is dissolved.

A slight excess of mineral acid is now added, and the whole heated until
the separated fatty acids are perfectly clear, when they are collected
on a tared filter paper, well washed with hot water and dried until
constant in weight. The result multiplied by 20 gives the percentage of
fatty acids in the sample.

A quicker method, and one which gives accurate results when care is
bestowed upon it, is to proceed in the manner described above as far as
the decomposition with mineral acid, and to then add 5 or 10 grammes of
stearic acid or beeswax to the contents of the beaker and heat until a
clear layer of fatty matter collects upon the acid liquor.

Cool the beaker, and when the cake is sufficiently hard, remove it
carefully by means of a spatula and dry on a filtering paper, add the
portions adhering to the sides of the beaker to the cake, and weigh.

The weight, less the amount of stearic acid or beeswax added, multiplied
by 20 gives the percentage of fatty acids.

Care must be taken that the cake does not contain enclosed water.

The results of these methods are returned as fatty acids, but are in
reality insoluble fatty acids, the soluble fatty acids being generally
disregarded. However in soaps made from cocoa-nut and palm-kernel oils
(which contain an appreciable quantity of soluble fatty acids) the acid
liquor is shaken with ether, and, after evaporation of the ethereal
extract, the amount of fatty matter left is added to the result already
obtained as above, or the ether method described below may be
advantageously employed.

Where the soap under examination contains mineral matter, the separated
fatty acids may be dissolved in ether. This is best performed in an
elongated, graduated, stoppered tube, the total volume of the ether,
after subsidence, carefully read, and an aliquot part taken and
evaporated to dryness in a tared flask, which is placed in the oven at
100° C. until the weight is constant.

In a complete analysis, the figure for fatty acids should be converted
into terms of fatty anhydrides by multiplying by the factor 0.9875.

In this test the resin acids contained in the soap are returned as fatty
acids, but the former can be estimated, as described later, and deducted
from the total.

_Total Alkali._--The best method is to incinerate 5 grammes of the soap
in a platinum dish, dissolve the residue in water, boil and filter,
making the volume of filtrate up to 250 c.c., the solution being
reserved for the subsequent determination of salt, silicates, and
sulphates, as detailed below.

Fifty c.c. of the solution are titrated with N/1 acid, to methyl orange,
and the result expressed in terms of Na_{2}O.

Number of c.c. required × 0.031 × 100 = per cent. Na_{2}O.

The total alkali may also be estimated in the filtrate from the
determination of fatty acids, if the acid used for decomposing the soap
solution has been measured and its strength known, by titrating back the
excess of acid with normal soda solution, when the difference will equal
the amount of total alkali in the quantity taken.

The total alkali is usually expressed in the case of hard soaps as
Na_{2}O, and in soft soaps as K_{2}O.

_Free caustic alkali_ is estimated by dissolving 2 grammes of the soap,
in neutral pure alcohol, with gentle heat, filtering, well washing the
filter with hot neutral spirit, and titrating the filtrate with N/10
acid, to phenol-phthalein.

Number of c.c. required × 0.0031 × 50 = per cent. free alkali Na_{2}O,
as caustic.

_Free Carbonated Alkali._--The residue on the filter paper from the
above determination is washed with hot water, and the aqueous filtrate
titrated with N/10 acid, using methyl orange as indicator. The result is
generally expressed in terms of Na_{2}O.

Number of c.c. required × 0.0031 × 50 = per cent. free alkali Na_{2}O,
as carbonate.

_Free Alkali._--Some analysts determine the alkalinity to
phenol-phthalein of the alcoholic soap solution without filtering, and
express it as free alkali (caustic, carbonates, or any salt having an
alkaline reaction).

_Combined Alkali._--The difference between total alkali and free alkali
(caustic and carbonate together) represents the alkali combined with
fatty acids. This figure may also be directly determined by titrating,
with N/2 acid, the alcoholic solution of soap after the free caustic
estimation, using lacmoid as indicator.

The potash and soda in soaps may be separated by the method described
for the estimation of potassium in _Pearl ash_ (page 126).

The potassium platino-chloride (K_{2}PtCl_{6}) is calculated to
potassium chloride (KCl) by using the factor 0.3052, and this figure
deducted from the amount of mixed chlorides found, gives the amount of
sodium chloride (NaCl), from which the sodium oxide (Na_{2}O) is
obtained by multiplying by 0.52991.

The potassium chloride (KCl) is converted into terms of potassium oxide
(K_{2}O) by the use of the factor 0.63087.

_Salt_ may be determined in 50 c.c. of the filtered aqueous extract of
the incinerated soap, by exactly neutralising with normal acid and
titrating with N/10 silver nitrate solution, using a neutral solution of
potassium chromate as indicator. The final reaction is more distinctly
observed if a little bicarbonate of soda is added to the solution.

Number of c.c. required × 0.00585 × 100 = per cent. of common salt,
NaCl.

Chlorides may also be estimated by Volhard's method, the aqueous extract
being rendered slightly acid with nitric acid, a measured volume of N/10
silver nitrate solution added, and the excess titrated back with N/10
ammonium thiocyanate solution, using iron alum as indicator.

_Silicates._--These are estimated by evaporating 50 c.c. of the filtered
extract from the incinerated soap, in a platinum dish with hydrochloric
acid twice to complete dryness, heating to 150° C., adding hot water,
and filtering through a tared filter paper.

The residue is well washed, ignited, and weighed as SiO_{2}, and from
this silica is calculated the sodium silicate.

_Sulphates_ may be determined in the filtrate from the silica estimation
by precipitation with barium chloride solution, and weighing the barium
sulphate, after filtering, and burning, expressing the result in terms
of Na_{2}SO_{4} by the use of the factor 0.6094.

_Moisture._--This is simply estimated by taking a weighed portion in
small shavings in a tared dish, and drying in the oven at 105° C. until
it ceases to lose weight. From the loss thus found is calculated the
moisture percentage.

_Free or Uncombined Fat._--This is usually determined by repeated
extraction of an aqueous solution of the soap with petroleum ether; the
ethereal solution, after washing with water to remove traces of soap, is
evaporated to dryness and the residue weighed.

A good method, which can be recommended for employment where many
determinations have to be performed, is to dissolve 10 grammes of soap
in 50 c.c. neutral alcohol and titrate to phenol-phthalein with N/1
acid. Add 3-5 drops HCl and boil to expel carbonic acid, neutralise with
alcoholic KOH solution and add exactly 10 c.c. in excess, boil for
fifteen minutes under a reflux condenser and titrate with N/1 acid. The
difference between this latter figure and the amount required for a
blank test with 10 c.c. alcoholic KOH, denotes the amount of alkali
absorbed by the uncombined fat.

_Examination of the fatty acids_ as a guide to the probable composition
of the soap:--

From the data obtained by estimating the "titre," iodine number, and
saponification equivalent of the mixed fatty and rosin acids, and the
rosin content, a fairly good idea of the constitution of the soap may be
deduced.

The titre, iodine number, and saponification equivalent are determined
in exactly the same manner as described under Fats and Oils.

The presence of rosin may be detected by the Liebermann-Storch reaction,
which consists in dissolving a small quantity of the fatty acids in
acetic anhydride, and adding to a few drops of this solution 1 drop of
50 per cent. sulphuric acid. A violet coloration is produced with rosin
acids. The amount of rosin may be estimated by the method devised by
Twitchell (_Journ. Soc. Chem. Ind._, 1891, 804) which is carried out
thus:--

Two grammes of the mixed fatty and rosin acids are dissolved in 20 c.c.
absolute alcohol, and dry hydrochloric acid gas passed through until no
more is absorbed, the flask being kept cool by means of cold water to
prevent the rosin acids being acted upon. The flask, after
disconnecting, is allowed to stand one hour to ensure complete
combination, when its contents are transferred to a Philips' beaker,
well washed out with water so that the volume is increased about five
times, and boiled until the acid solution is clear, a fragment of
granulated zinc being added to prevent bumping. The heat is removed, and
the liquid allowed to cool, when it is poured into a separator, and the
beaker thoroughly rinsed out with ether. After shaking, the acid liquor
is withdrawn, and the ethereal layer washed with water until free from
acid. Fifty c.c. neutral alcohol are added, and the solution titrated
with N/1 KOH or NaOH solution, the percentage of rosin being calculated
from its combining weight. Twitchell suggests 346 as the combining
weight of rosin, but 330 is a closer approximation.

The method may be also carried out gravimetrically, in which case
petroleum ether, boiling at 74° C. is used for washing out the beaker
into the separator. The acid liquor is run off, and the petroleum ether
layer washed first with water and then with a solution of 1/2 gramme KOH
and 5 c.c. alcohol in 50 c.c. water, and agitated. The rosin is thus
saponified and separated. The resinate solution is withdrawn, acidified,
and the resin acids collected, dried and weighed.

_Halphen's Reaction._--This is a special test to determine the presence
or absence of cotton-seed oil fatty acids in mixtures. Equal parts of
the fatty acids, amyl alcohol, and a 1 per cent. solution of sulphur in
carbon bisulphide, are heated in a test-tube placed in a water-bath
until effervescence ceases, then in boiling brine for one hour or longer
when only small quantities are present. The presence of cotton-seed oil
is denoted by a pink coloration. The reaction is rendered much more
rapid, according to Rupp (_Z. Untersuch. Nahr. Genussm._, 1907, 13, 74),
by heating in a stoppered flask.

Other bodies which it is occasionally necessary to test for or determine
in soap include:--

_Carbolic acid._--Fifty grammes of the soap are dissolved in water and
20 c.c. of 10 per cent. caustic potash added. The solution is treated
with an excess of brine, the supernatant liquor separated, and the
precipitate washed with brine, the washings being added to the liquor
withdrawn. This is then evaporated to a small bulk, placed in a Muter's
graduated tube, and acidified with mineral acid.

The volume of separated phenols is observed and stated in percentage on
the soap taken.

Or the alkaline layer may be rendered acid and steam distilled; the
distillate is made up to a known volume, and a portion titrated by the
Koppeschaar method with standard bromine water.

_Glycerine._--Five grammes of soap are dissolved in water, decomposed
with dilute sulphuric acid, and the clear fatty acids filtered and
washed. The filtrate is neutralised with barium carbonate, evaporated
to 50 c.c., and the glycerol estimated by the bichromate method detailed
under Crude Glycerine.

_Starch_ or _gum_ may be detected by dissolving the soap in alcohol,
filtering, and examining the residue on the filter paper. Starch is
readily recognised by the blue coloration it gives with a solution of
iodine in potassium iodide.

_Sugars_ are tested for by means of Fehlings' solution, in the liquor
separated from the fatty acids, after first boiling with dilute acid to
invert any cane sugar.

_Mercury_ will be revealed by a black precipitate produced when
sulphuretted hydrogen is added to the liquor separated from the fatty
acids, and may be estimated by filtering off this precipitate on a tared
Gooch's crucible, which is then dried and weighed.

_Borax or borates_ are tested for in the residue insoluble in alcohol.
This is dissolved in water, rendered faintly acid with dilute
hydrochloric acid, and a strip of turmeric paper immersed for a few
minutes in the liquid. This is then dried in the water-oven, when if any
boric acid compound is present, a bright reddish-pink stain is produced
on the paper, which is turned blue on moistening with dilute alkali.

The amount of the boric acid radicle may be determined by incinerating
5-10 grammes of soap, extracting with hot dilute acid, filtering,
neutralising this solution to methyl orange, and boiling to expel carbon
dioxide. After cooling, sufficient pure neutralised glycerine is added
to form one-third of the total volume, and the liquid titrated with N/2
caustic soda solution, using phenol-phthalein as indicator. Each c.c. of
N/2 NaOH solution corresponds to 0.031 gramme crystallised boric acid,
H_{3}BO_{3} or 0.0477 gramme crystallised borax,
Na_{2}B_{4}O_{7}·10H_{2}O.


LYES.

The amounts of caustic alkali (if any), carbonated alkali, and salt
present are determined in the manner already described under Alkali and
Alkali Salts. The glycerol content is ascertained by taking 2.5 grammes,
adding lead subacetate solution, and filtering without increasing the
bulk more than is absolutely necessary; the solution is concentrated to
about 25 c.c., and the oxidation with bichromate and sulphuric acid
conducted as described in the examination of Crude Glycerine. The
solution, after oxidation, is made up to 250 c.c., and titrated against
standard ferrous ammonium sulphate solution, the formula for the
calculation being:--

                                  {0.25 - 2.5}
          Per cent. of glycerol = {       ---} × 40
                                  {        n }

where n equals the number of c.c. of oxidised lyes required to oxidise
the ferrous ammonium sulphate solution.

The estimation of actual glycerol in this is necessarily a matter of
considerable importance, and a very large number of processes, which are
constantly being added to, have been suggested for the purpose.
Hitherto, however, only two methods have been generally adopted, _viz._
the acetin and the bichromate processes. Unfortunately the results
obtained by these do not invariably agree, the latter, which includes
all oxidisable matter as glycerol, giving sometimes considerably higher
results, and it has been suggested that a determination should be made
by both methods, and the average of the two results considered the true
value. This involves a considerable amount of time and trouble, and it
will generally be found sufficient in a works laboratory to determine
the glycerol by one method only in the ordinary course, reserving the
other process for use as a check in case of dispute or doubt.

_Acetin Method._--This consists in converting the glycerol into its
ester with acetic acid, the acetic triglyceride, or triacetin being
formed. This is then saponified with a known volume of standard alkali,
the excess of which is titrated with acid, and the percentage of
glycerol calculated from the amount of alkali absorbed.

From 1 to 1.5 grammes of the glycerine is weighed into a conical flask
of about 150 c.c. capacity, 7 or 8 c.c. of acetic anhydride added,
together with about 3 grammes of anhydrous sodium acetate, and the whole
boiled on a sand-bath under a reflux condenser for one to one and a half
hours, after which it is allowed to cool, 50 c.c. water added, and the
ester dissolved by shaking, and gently warming, the reflux condenser
still being attached as the acetin is very volatile. The solution is
then filtered from a white flocculent precipitate, which contains most
of the impurities, into a larger conical flask, of some 500-600 c.c.
capacity, and after cooling, rendered just neutral to phenol-phthalein
by means of N/2 caustic soda solution, the exact point being reached
when the solution acquires a reddish-yellow tint; 25 c.c. of a strong
caustic soda solution is then added, and the liquid boiled for about
fifteen minutes, the excess of alkali being titrated after cooling, with
N/1 or N/2 hydrochloric acid. A blank experiment is carried out
simultaneously, with another 25 c.c. of the soda solution, and the
difference in the amounts of acid required by the two, furnishes a
measure of the alkali required to saponify the acetin formed, and hence
the amount of glycerol in the crude glycerine may be calculated.

_Example._--1.4367 grammes crude glycerine, after treatment with acetic
anhydride, and neutralising, was saponified with 25 c.c. of a 10 per
cent. caustic soda solution.

       The blank experiment required 111.05 c.c. N/1 hydrochloric acid.
       Flask containing acetin  "     75.3  c.c.   "        "
                                      -----
                                      35.75 c.c.   "        "

Hence, the acetin formed from the glycerol present in 1.4367 grammes of
the crude glycerine required 35.75 c.c. N/1 caustic alkali for its
saponification, so that the percentage of glycerol may be calculated
from the following formula:--

                                35.75 × 0.03067 × 100
          Per cent. glycerol =  --------------------- = 76.3.
                                        1.4367

_Bichromate Method._--This process was originally devised by Hehner
(_Journ. Soc. Chem. Ind._, 1889, 4-9), but the modification suggested by
Richardson and Jaffe (_ibid._, 1898, 330) is preferred by the authors,
and has been practised by them for several years with perfectly
satisfactory results.

Twenty-five grammes of the crude glycerine are weighed out in a beaker,
washed into a 250 c.c. stoppered flask, and made up to the graduation
mark with water. Twenty-five c.c. of this solution are then measured
from a burette into a small beaker, a slight excess of basic lead
acetate solution added to precipitate organic matter, the precipitate
allowed to settle, and the supernatant liquid poured through a filter
paper into another 250 c.c. flask. The precipitate is washed by
decantation until the flask is nearly full, then transferred to the
filter, and allowed to drain, a few drops of dilute sulphuric acid being
added to precipitate the slight excess of basic lead acetate solution,
and the contents of the flask made up with water to 250 c.c. This
solution is filtered, 20 c.c. measured from a burette into a conical
flask of about 150 c.c. capacity, 25 c.c. of a standard potassium
bichromate solution containing 74.86 grammes bichromate per litre added,
together with 50 c.c. of 50 per cent. sulphuric acid, and the whole
placed in a boiling water-bath for one hour, after which it is allowed
to cool, diluted with water to 250 c.c., and this solution run in to 20
c.c. of a 3 per cent. ferrous ammonium sulphate solution until the
latter is completely oxidised, as shown by no blue coloration being
produced when one drop is brought into contact with one drop of a
freshly prepared solution of potassium ferricyanide on a spot-plate. The
ferrous ammonium sulphate solution is previously standardised by
titration with a potassium bichromate solution of one-tenth the above
strength, made by diluting 10 c.c. of the strong solution to 100 c.c.
with water.

The reaction taking place in the oxidation may be represented by the
equation:--

    3C_{3}H_{5}(OH)_{3} + 7K_{2}Cr_{2}O_{7} + 28H_{2}SO_{4} =
        9CO_{2} + 40H_{2}O + 7K_{2}SO_{4} + 7Cr_{2}(SO_{4})_{3}.

Now the strong potassium bichromate solution above mentioned is of such
a strength that 1 c.c. will oxidise 0.01 gramme glycerine, and 20 c.c.
of the ferrous ammonium sulphate solution should require about 10 c.c.
of the one-tenth strength bichromate in the blank experiment. If it
requires more or less than this, then the amount of ferrous ammonium
sulphate solution which would require exactly 10 c.c. (corresponding to
0.01 gramme glycerine) is calculated, and the oxidised glycerine
solution run into this until oxidation is complete.

The formula for the calculation of the percentage of glycerol then
becomes:--

                                  {0.25 -(250 × 0.01)}
          Per cent. of glycerol = {       ---------- } × 500,
                                  {            n     }

where n equals the number of c.c. of oxidised glycerine solution
required to oxidise the ferrous ammonium sulphate solution.

Example:--

In the blank experiment 20 c.c. ferrous ammonium sulphate solution
required 9.8 c.c. one-tenth strength bichromate solution, so that 20.4
c.c. ferrous solution would equal 10 c.c. bichromate.

20.4 c.c. ferrous solution required 27.8 c.c. of oxidised glycerine
solution before it ceased to give a blue coloration with potassium
ferricyanide.
                                        {0.25 - (250 × 0.01)}
    Therefore, per cent. of glycerol = {       ------------} × 500
                                       {           27.8    }

                                     = 80.04 per cent.

Other methods have been suggested for the preliminary purification,
_e.g._, silver oxide, silver carbonate and lead subacetate, and copper
sulphate and caustic potash, but the lead subacetate alone with care
gives satisfactory results.

Other determinations include those of specific gravity, alkalinity,
proportion of salts and chloride, and tests for metals, arsenic, sulphur
compounds, sugar, and fatty acids.

_Specific gravity_ is determined at 15° C., and may be taken in specific
gravity bottle, or with a Westphal balance or hydrometer It usually
ranges from 1.3 to 1.31.

_Alkalinity_, which is usually sodium carbonate, and may be somewhat
considerable if the soap has been grained with caustic alkali, is
determined after dilution with water by titrating with N/2 acid, using
methyl orange as indicator.

_Salts._--These may be determined by gently incinerating 5-6 grammes of
the glycerine, extracting the carbonaceous mass with distilled water,
filtering, and evaporating the filtrate on the water bath. The dried
residue represents the salts in the weight taken.

_Chloride of sodium_ (common salt) may be estimated by dissolving the
total salts in water, adding potassium chromate, and titrating with N/10
silver nitrate solution.

_Copper_, _lead_, _iron_, _magnesium_, and _calcium_ may also be tested
for in the salts, by ordinary reactions.

_Arsenic_ is best tested for by the Gutzeit method. About 5 c.c. is
placed in a test-tube, a few fragments of granulated zinc free from
arsenic, and 10 c.c. dilute hydrochloric acid added, and the mouth of
the tube covered with a small filter paper, moistened three successive
times with an alcoholic solution of mercury bichloride and dried. After
thirty minutes the filter paper is examined, when a yellow stain will be
observed if arsenic is present.

_Sulphates._--These may be precipitated with barium chloride in acid
solution, in the usual way, dried, ignited, and weighed.

_Sulphites_ give with barium chloride a precipitate soluble in
hydrochloric acid. If the precipitate is well washed with hot water, and
a few drops of iodine solution together with starch paste added, the
presence of sulphites is proved by the gradual disappearance of the blue
starch-iodine compound first formed.

_Thiosulphates_ are detected by precipitating any sulphite and sulphate
with barium chloride, filtering, acidifying, and adding a few drops of
potassium permanganate solution, when in the presence of a mere trace of
thiosulphate, the solution becomes cloudy.

_Sulphides._--Lewkowitsch recommends testing for these by replacing the
mercury bichloride with lead acetate paper in the Gutzeit arsenic test.
Any sulphide causes a blackening of the lead acetate paper.

_Sugars_ may be tested for both before and after inversion, by boiling
with Fehlings' solution, when no reduction should take place, if pure.

_Fatty acids_ are detected by the turbidity they produce when the
diluted glycerine is acidified.



CHAPTER XI.

STATISTICS OF THE SOAP INDUSTRY.


Until the year 1853 the amount of soap produced annually in this country
was readily obtainable from the official returns collected for the
purpose of levying the duty, and the following figures, taken at
intervals of ten years for the half century prior to that date, show the
steady development of the industry during that period:--

 _______________________________________________________________
|       |               |           |           |               |
| Year. | Manufactured. | Consumed. | Exported. | Duty per Ton. |
|_______|_______________|___________|___________|_______________|
|       |               |           |           |               |
|       |     Cwts.     |   Cwts.   |   Cwts.   |      £        |
| 1801  |     509,980   |   482,140 |   26,790  |      21       |
| 1811  |     678,570   |   651,780 |   26,790  |      21       |
| 1821  |     875,000   |   839,290 |   35,710  |      28       |
| 1831  |   1,098,210   |   955,360 |  142,850  |      28       |
| 1841  |   1,776,790   | 1,517,860 |  258,930  |      14       |
| 1851  |   1,937,500   | 1,741,070 |  196,430  |      14       |
|_______|_______________|___________|___________|_______________|

Since the repeal of the soap duty, the revenue from which had reached
about £1,000,000 per annum, no accurate means of gauging the production
exists, but it is estimated that it has nearly quadrupled during the
last fifty-five years, being now some 7,000,000 or 8,000,000 cwt. per
annum.

The number of soap manufacturers in the United Kingdom is nearly 300,
and the amount of capital invested in the industry is roughly estimated
to approach £20,000,000 sterling.

Official figures are still available for the amount and value of soap
annually imported and exported to and from the United Kingdom, the
returns for the last eight years being:--

_Imports._
_________________________________________________________________________
|       |                     |                     |                     |
|       |       Household.    |         Toilet.     |       Total.[13]    |
|       |_____________________|_____________________|_____________________|
| Year. |           |         |           |         |           |         |
|       | Quantity. |  Value. | Quantity. |  Value. | Quantity. |  Value  |
|_______|___________|_________|___________|_________|___________|_________|
|       |           |         |           |         |           |         |
|       |   Cwts.   |    £    |   Cwts.   |    £    |   Cwts.   |    £    |
|  1900 |    ...    |   ...   |    ...    |   ...   |  191,233  | 244,345 |
|  1901 |    ...    |   ...   |    ...    |   ...   |  302,555  | 315,026 |
|  1902 |    ...    |   ...   |    ...    |   ...   |  361,851  | 429,300 |
|  1903 |  273,542  | 284,376 |  25,749   |  98,032 |  462,959  | 499,407 |
|  1904 |  254,425  | 268,408 |  17,962   |  81,162 |  383,122  | 438,966 |
|  1905 |  274,238  | 279,044 |  19,631   |  98,507 |  473,067  | 500,430 |
|  1906 |  309,975  | 311,114 |  18,554   | 101,243 |  399,070  | 468,086 |
|  1907 |  228,035  | 263,965 |  18,244   |  99,432 |  504,710  | 545,385 |
|_______|___________|_________|___________|_________|___________|_________|

Household and toilet soaps were not given separately prior to 1903.

The imports during the last three years for which complete figures are
obtainable, came from the following sources:--

_Household Soap._
 ______________________________________________________________
|                                |         |         |         |
|                                |   1904. |   1905. |   1906. |
|________________________________|_________|_________|_________|
|                                |         |         |         |
|                                |    £    |    £    |    £    |
| From Netherlands               |   4,315 |   3,620 |   3,368 |
|      France                    |  14,339 |  17,783 |  24,747 |
|      Italy                     |  24,209 |  18,129 |  32,972 |
|      United States             | 218,740 | 235,612 | 242,294 |
|      Other Foreign Countries   |   6,785 |   3,873 |   7,448 |
|                                |_________|_________|_________|
|                                |         |         |         |
| Total from Foreign Countries   | 268,388 | 279,017 | 310,829 |
| Total from British Possessions |      20 |      27 |     285 |
|                                |_________|_________|_________|
|                                |         |         |         |
| Total                          | 268,408 | 279,044 | 311,114 |
|________________________________|_________|_________|_________|


_Toilet Soap._
 ______________________________________________________________
|                                |         |         |         |
|                                |   1904. |   1905. |   1906. |
|________________________________|_________|_________|_________|
|                                |         |         |         |
|                                |    £    |    £    |    £    |
|  From Germany                  |   3,509 |   3,516 |   3,001 |
|       Netherlands              |   5,937 |   5,773 |   5,919 |
|       Belgium                  |   1,568 |   1,861 |   3,145 |
|       France                   |   7,120 |   7,633 |   5,794 |
|       Italy                    |   1,176 |     255 |   1,233 |
|       United States            |  59,863 |  74,516 |  78,382 |
|       Other Foreign Countries  |     166 |     147 |     196 |
|                                |_________|_________|_________|
|                                |         |         |         |
| Total from Foreign Countries   |  79,339 |  93,701 |  97,670 |
| Total from British Possessions |   1,823 |   4,411 |   3,225 |
|                                |_________|_________|_________|
|                                |         |         |         |
| Total                          |  81,162 |  98,112 | 100,895 |
|________________________________|_________|_________|_________|


_Exports._

The exports from the United Kingdom during the past eight years have
been as follows:--

 _________________________________________________________________________
|     |                       |                    |                      |
|     |        Household.     |       Toilet.      |       Total.[14]     |
|     |_______________________|____________________|______________________|
|Year.|           |           |          |         |           |          |
|     | Quantity. |   Value.  | Quantity.|  Value. | Quantity. |  Value.  |
|_____|___________|___________|__________|_________|___________|__________|
|     |           |           |          |         |           |          |
|     |   Cwts.   |     £     |   Cwts.  |    £    |   Cwts.   |     £    |
| 1900|    ...    |    ...    |    ...   |   ...   |   874,214 |   939,510|
| 1901|    ...    |    ...    |    ...   |   ...   |   947,485 |   999,524|
| 1902|    ...    |    ...    |    ...   |   ...   | 1,051,624 | 1,126,657|
| 1903|   998,995 |   900,814 |   38,372 | 217,928 | 1,057,164 | 1,143,661|
| 1904| 1,049,022 |   955,774 |   40,406 | 228,574 | 1,108,174 | 1,208,712|
| 1905| 1,167,976 | 1,013,837 |   43,837 | 248,425 | 1,230,310 | 1,284,727|
| 1906| 1,131,294 | 1,009,653 |   46,364 | 261,186 | 1,210,598 | 1,309,556|
| 1907| 1,114,624 | 1,095,170 |   50,655 | 280,186 | 1,240,805 | 1,459,113|
|_____|___________|___________|__________|_________|___________|__________|

Household and toilet soaps were not given separately prior to 1903.

The exports for the last three years for which complete figures are
available, consisted of the following:--

_Household Soap._

+----------------------------------------+----------+----------+-----------+
|                                        |   1904.  |   1905.  |    1906.  |
+----------------------------------------+----------+----------+-----------+
|                                        |    £     |    £     |     £     |
|To Sweden                               |   3,027  |   2,911  |    3,677  |
|   Norway                               |   4,173  |   3,921  |    6,005  |
|   Netherlands                          |  39,420  |  41,197  |   48,601  |
|   Dutch Possessions in the Indian Seas |   8,586  |  10,293  |    7,746  |
|   Belgium                              |  73,996  |  51,583  |    7,729  |
|   France                               |  11,741  |  12,222  |   22,907  |
|   Portuguese East Africa               |  28,987  |  42,981  |   40,478  |
|   Canary Islands                       |  24,763  |  27,864  |   27,579  |
|   Italy                                |   2,842  |   3,187  |    3,962  |
|   Turkey                               |   6,974  |   7,858  |    5,897  |
|   Egypt                                |  12,110  |   9,467  |   12,035  |
|   China (exclusive of Hong-Kong and    |          |          |           |
|     Macao)                             |  49,235  | 114,156  |   89,169  |
|   United States                        |   3,885  |   1,975  |    3,924  |
|   Columbia                             |   3,601  |     501  |    1,364  |
|   Ecuador                              |   3,075  |   3,096  |    6,861  |
|   Chili                                |   5,972  |   4,865  |    9,203  |
|   Brazil                               |  35,197  |  28,198  |   31,726  |
|   Argentine Republic                   |   7,802  |   8,954  |   13,084  |
|   Other Foreign Countries              |  40,058  |  53,914  |   77,687  |
|                                        +----------+----------+-----------+
|Total to Foreign Countries              | 365,444  | 429,143  |  419,634  |
|                                        +---------------------------------+
|To Channel Islands                      |   5,301  |   8,328  |    7,968  |
|   Gibraltar                            |  13,272  |  13,868  |   12,661  |
|   British West Africa--                |          |          |           |
|     Gold Coast                         |   22,598 |   18,513 |   23,423  |
|     Lagos                              |    7,751 |    8,032 |    9,518  |
|     Nigerian Protectorate              |   14,942 |   15,299 |   20,951  |
|   Cape of Good Hope                    |  158,517 |  143,750 |  136,388  |
|   Natal                                |   74,848 |   71,874 |   46,771  |
|   British India                        |          |          |           |
|     Bombay (including Kurachi)         |   59,406 |   68,945 |   77,867  |
|     Madras                             |    6,364 |    6,697 |   10,355  |
|     Bengal, Eastern Bengal and Assam.  |   26,534 |   23,087 |   22,648  |
|     Burmah                             |   26,389 |   35,727 |   37,103  |
|   Straits Settlements and Dependencies |   26,516 |   32,214 |   39,749  |
|   Hong-Kong                            |   14,119 |   15,153 |   15,685  |
|   British West India Islands           |   74,069 |   58,881 |   67,331  |
|   British Guiana                       |   12,661 |   12,023 |   11,557  |
|   Other British Possessions            |   47,043 |   52,303 |   50,044  |
|                                        +----------+----------+-----------+
|Total to British Possessions            |  590,330 |  584,694 |  590,019  |
|                                        +----------+----------+-----------+
|                 Total                  |  955,774 |1,013,837 |1,009,653  |
|----------------------------------------+---------+-----------+-----------+

_Toilet Soap._
 ________________________________________________________________
|                                  |         |         |         |
|                                  |   1904. |   1905. |   1906. |
|__________________________________|_________|_________|_________|
|                                  |         |         |         |
|                                  |    £    |    £    |    £    |
| To Germany                       |   5,051 |   6,322 |   6,620 |
|    Belgium                       |   3,730 |   3,265 |   3,355 |
|    France                        |   7,903 |   8,988 |   9,324 |
|    Portuguese East Africa        |   2,215 |   3,973 |   4,658 |
|    Egypt                         |   2,302 |   3,350 |   3,525 |
|    China (exclusive of           |         |         |         |
|      Hong-Kong and Macao)        |   3,096 |   3,115 |   3,645 |
|    Japan (including Formosa)     |   3,300 |   4,649 |   3,382 |
|    United States                 |  50,043 |  50,668 |  52,124 |
|    Brazil                        |   1,879 |   2,241 |   2,292 |
|    Other Foreign Countries       |  22,002 |  26,081 |  29,214 |
|                                  |_________|_________|_________|
|                                  |         |         |         |
| Total to Foreign Countries       | 101,521 | 112,652 | 118,139 |
|                                  |_________|_________|_________|
|                                  |         |         |         |
| To Cape of Good Hope             |  14,094 |  14,815 |  14,988 |
|    Natal                         |   8,897 |  11,913 |   7,280 |
|    British India--               |         |         |         |
|      Bombay (including Kurachi)  |  24,665 |  24,672 |  28,316 |
|      Madras                      |   4,333 |   5,851 |   6,624 |
|      Bengal, Eastern Bengal      |         |         |         |
|        and Assam                 |  14,129 |  16,021 |  15,969 |
|      Burmah                      |   3,299 |   3,400 |   4,667 |
|    Straits Settlements and       |         |         |         |
|      Dependencies                |   3,590 |   5,092 |   4,798 |
|    Ceylon and Dependencies       |  12,210 |  11,118 |  12,854 |
|    Australia--                   |         |         |         |
|      Western Australia           |   1,549 |   1,394 |   1,137 |
|      South Australia, (including |         |         |         |
|        Northern Territory)       |     895 |     644 |     637 |
|      Victoria                    |  11,989 |  13,614 |  12,774 |
|      New South Wales             |   3,920 |   4,278 |   4,139 |
|      Queensland                  |     957 |   1,097 |   1,108 |
|      Tasmania                    |     482 |     315 |     547 |
|    New Zealand                   |   5,093 |   4,498 |   5,503 |
|    Canada                        |   6,382 |   6,196 |   8,185 |
|    Other British Possessions     |  11,069 |  10,855 |  13,521 |
|                                  |_________|_________|_________|
|                                  |         |         |         |
| Total to British Possessions     | 127,053 | 135,773 | 143,047 |
|                                  |_________|_________|_________|
|                                  |         |         |         |
|                  Total           | 228,574 | 248,425 | 261,186 |
|__________________________________|_________|_________|_________|

The following statistics extracted from official consular reports, etc.,
show the extent of the soap industry in other parts of the world.

_United States._--According to the _Oil, Paint and Drug Report_ the
total production of soap in the United States during 1905, exclusive of
soap products to the value of $1,437,118 made in establishments engaged
primarily in the manufacture of other products, reached a value of
$68,274,700, made up in the following manner:--

+------------------------------------+--------------+-------------+
|                                    |   Quantity.  |     Value.  |
+------------------------------------+--------------+-------------+
|                                    |      Lbs.    |       $     |
|Hard soaps                          |      ...     |  56,878,486 |
|Tallow soap                         | 846,753,798  |  32,610,850 |
|Olein soap                          |  29,363,376  |   1,363,636 |
|Foots soap                          |  85,000,133  |   3,090,312 |
|Toilet soaps, including medicated,  |              |             |
|  shaving, and other special soaps  | 130,225,417  |   9,607,276 |
|Powdered soaps, sold as such        | 120,624,968  |   4,358,682 |
|All other soaps                     | 143,390,957  |   6,097,670 |
|Soft soap                           |  33,613,416  |     667,064 |
|Special soap articles               |     ...      |     554,881 |
+------------------------------------+--------------+-------------+

_France_.--This country exported common soap during 1906 to the value of
£556,000, or £8,000 more than in 1905.

The chief centre of the soap industry is Marseilles, which, with about
fifty soap factories, produces annually some 3,000,000 cwts.

_Germany_ imported in 1905 soap and perfumery to the value of £3,032,
that exported amounting to £15,364.

In Saxony there are eighty soap factories.

_Russia._--There are fifty large soap factories in Russia, the annual
output from which is about 2,250,000 cwt.

_Roumania._--This country possesses about 230 small and eighteen large
soap and candle factories, most of which produce only common soap, there
being only one firm--in Bucharest--which makes milled soaps.

_Denmark._--In this country there are some 200 small soap factories.

_Australia._--According to a Board of Trade report, there were
ninety-eight soap and candle factories in Australia in 1905, employing
1,568 hands, and producing 495,036 cwt. of soap.

_Queensland._--In 1905 this country contained twenty-one soap and candle
works, in which 142 hands were employed, and having an output valued at
£86,324.

_Hong-Kong._--There are about twenty-four soap factories on this island.

_Japan._--A Swiss consular report states that in Japan there are now
some fifty soap works, producing about 15,000,000 tablets monthly.

_Fiji Islands._--These possess only one soap factory, the output from
which is 9 cwt. daily.

The following table, compiled from various consular and other official
returns, shows the quantity and value of soap imported into different
countries and places during the years 1905-7:--

 _______________________________________________________________________________
                  |                   |                    |
                  |     Household.    |        Toilet.     |       Total.
                  |___________________|____________________|____________________
 Place and Date.  |          |        |         |          |         |
                  | Quantity.| Value. |Quantity.|  Value.  |Quantity.|  Value.
__________________|__________|________|_________|__________|_________|__________
                  |          |        |         |          |         |
_Europe_--        |          |        |         |          |         |
 Cyprus, 1905     |   ...    |  ...   |   ...   |   ...    |   ...   |    £9,983
 Iceland, 1906    |   ...    |  ...   |   ...   |   ...    |   ...   |    £6,423
 Switzerland,     |   ...    |  ...   |   ...   |   ...    |1,702,800|     ...
   1906           |          |        |         |          |  kilos. |     ...
 Turkey           |   ...    |  ...   |   ...   |   ...    |   About |     ...
                  |          |        |         |          |1,800,000|     ...
                  |          |        |         |          | lb. per |
                  |          |        |         |          |  annum  |
_Africa_--        |          |        |         |          |         |
  Algeria, 1906   |  13,609  |£228,640|   ...   |   ...    |    ...  |     ...
                  |   tons   |        |         |          |         |
  Cape Colony,    |15,897,800|£145,000| 427,600 |   ...    |    ...  |     ...
    1906          |    lb.   |        |   lb.   |          |         |
  Gold Coast, 1906|   ...    |  ...   |    ...  |   ...    |    ...  |   £23,987
  Lourenço,       | 357,638  | £4,293 |  36,000 |  £2,195  |    ...  |     ...
     Marques, 1906|    lb.   |        |    lb.  |          |         |
  Natal, 1906     |4,263,000 |  ...   |   9,870 |   ...    |    ...  |     ...
                  |   lb.    |        |    lb.  |          |         |
  Orange River    | 2,382,000| £23,000|1,748 lb.|   ...    |    ...  |     ...
    Colony, 1906  |    lb.   |        |         |          |         |
  Pemba, 1905     |   ...    |  ...   |   ...   |   ...    |    ...  |    £1,092
  Rhodesia, 1906  |  257,600 |  ...   |2,909 lb.|   ...    |    ...  |     ...
                  |     lb.  |        |         |          |         |
  Southern        |          |        |         |          |         |
     Nigeria, 1905|   ...    |  ...   |   ...   |   ...    |    ...  |   £11,990
  Tangier         |   ...    |  ...   |   ...   |   ...    |    ...  |    £4,554
  Transvaal, 1906 | 4,407,000| £81,000| 202,200 |   ...    |    ...  |     ...
                  |    lb.   |        |    lb.  |          |         |
  Tripoli, 1905   |   ...    |  ...   |   ...   |   ...    |    ...  |    £6,080
  Tunis, 1906     |   ...    |  ...   |   ...   |   ...    |  1,539  |   £23,727
                  |          |        |         |          |   tons  |
  Zanzibar, 1906  |   ...    |  ...   |   ...   |   ...    |    ...  |    £6,102
                  |          |        |         |          |         |
_America_--       |          |        |         |          |         |
  Bahia, 1906     |   ...    |  ...   |   ...   |   ...    |   1,031 |   606,046
                  |          |        |         |          |    tons |   milreis
  Brazil, 1906    |   ...    |  ...   |   ...   |   ...    |   1,782 |     ...
                  |          |        |         |          |    tons |
                  |          |        |         |          |from U.K.|
  British Guiana, |          |        |         |          |         |
    1906-7        |   ...    |  ...   |   ...   |   ...    |   ...   |   £13,733
  Canada, 1906-7  |   ...    |  ...   |   ...   |   ...    |   ...   |  $600,999
  Columbia, 1906--|          |        |         |          |         |
    Cartagena     |   ...    |  ...   |   ...   |   ...    |  65,991 |     ...
                  |          |        |         |          |   tons  |
    Barranquilla  |   ...    |  ...   |   ...   |   ...    | 814,671 |   $14,712
                  |          |        |         |          |    lb.  |
  Costa Rica, 1906|   ...    |  ...   |   ...   |   ...    |   ...   |    £1,269
                  |          |        |         |          |         | from U.K.
                  |          |        |         |          |         |
  Ecuador, 1904   |   ...    |  ...   |   ...   |   ...    | 759,034 |     ...
                  |          |        |         |          |  kilos. |
  Granada, 1905   |   ...    |  ...   |   ...   |   ...    |   ...   |    £3,867
  Guatemala, 1906 |   ...    |  £900  |   ...   |   ...    |   ...   |     ...
  Martinique, 1906|  693,269 | £6,955 |   ...   |   ...    |   ...   |     ...
                  |   kilos. |        |         |          |         |
  Mexico, 1905-6  |   ...    | £5,982 |   ...   |   ...    |   ...   |     ...
  San Domingo,    |   ...    |  ...   |   ...   |   ...    | 754,587 |
    1906          |          |        |         |          |    lb.  |     ...
  St. Vincent,    |          |        |         |          |         |
    1905-6        |   ...    |  ...   |   ...   |   ...    |   ...   |    £1,375
  Surinam, 1906   |   ...    | £3,905 |   1,142 |   ...    |   ...   |     ...
                  |          |        |    tons |          |         |
  Trinidad, 1906-7|   ...    |  ...   |   ...   |   ...    |   ...   |   £29,967
  United States,  |          |        |         |          |         |
    1905          |   ...    |$399,797|   ...   |$1,071,446|   ...   |$1,471,243
__________________|__________|________|_________|__________|_________|____________

________________________________________________________________________________
                  |                  |                 |
                  |    Household.    |      Toilet.    |       Total
                  |__________________|_________________|________________________
 Place and Date.  |          |       | Quan- |         |  Quan- |
                  | Quantity.| Value.| tity. |  Value. |  tity  |   Value.
__________________|__________|_______|_______|_________|________|_______________
                  |          |       |       |         |        |
_Asia_--          |          |       |       |         |        |
  Ceylon, 1906    |    ...   |  ...  |  ...  |   ...   |  ...   | 423,700 rupees
  China, 1906     |    ...   |  ...  |  ...  |   ...   |  ...   |£216,042
  Hangchow, 1906  |    ...   |  ...  |  ...  |   ...   |  ...   |  £5,888
  India, 1906-7   |    ...   |   ... |  ...  |   ...   | 183,998| £215,210
                  |          |       |       |         |   cwts.|
  Kiungchow, 1905 |    ...   |  £575 |  ...  |    ...  |  ...   |  ...
  Shanghai, 1905  |    ...   |   ... |  ...  |    ...  |  ...   | £93,256
  Smyrna, 1906    |    ...   |   ... |  ...  |    ...  |261 tons|  ...
                  |          |       |       |         |        |
_Australasia_--   |          |       |       |         |        |
  Australia, 1906 |    ...   |  ...  |891,117| £65,840 |  ...   |  ...
                  |          |       |   lb. |         |        |
  Fiji, 1906      |    ...   |  ...  |  ...  |  ...    |  ...   |  £1,760
  New Zealand,    |          |       |       |         |        |
    1905          |    ...   |  ...  |  ...  |  ...    |  ...   | £36,843
  Philippine      |          |       |       |         |        |
    Islands, 1905 |    ...   |  ...  |  ...  |   ...   |  ...   |  £9,137
__________________|__________|_______|_______|_________|________|________


_Exports._
________________________________________________________________________________
                   |                   |                  |
                   |     Household.    |       Toilet.    |      Total
                   |___________________|__________________|_____________________
  Place and Date.  |          |        | Quan- |          | Quan- |
                   | Quantity.| Value. | tity. |  Value.  | tity. |  Value
___________________|__________|________|_______|__________|_______|_____________
                   |          |        |       |          |       |
_Europe_--         |          |        |       |          |       |
  Candia, Crete,   |   ...    |   ...  |  ...  |    ...   | 2,200 |   £34,000
    1906           |          |        |       |          | tons. |
  Greece           |   ...    |   ...  |  ...  |    ...   |  ...  |    About
                   |          |        |       |          |       |  500,000 Fr.
                   |          |        |       |          |       |  per annum.
  Italy, 1907      | 3,992,800| £95,840|  ...  |    ...   |  ...  |    ...
                   |   kilos. |        |       |          |       |
  Leghorn, 1906    |    ...   |   ...  |  ...  |    ...   | 1,521 |   £37,065
                   |          |        |       |          | tons. |
  Spain, 1905      | 4,750,996| £98,840|  ...  |    ...   |  ...  |     ...
                   |   kilos. |        |       |          |       |
  Switzerland, 1906|    ...   |   ...  |  ...  |    ...   | 77,300|     ...
                   |          |        |       |          | kilos.|
_Africa_--         |          |        |       |          |       |
  Cape Colony, 1906|  200 lb. |   ...  |  ...  |    ...   |  ...  |     ...
  Natal, 1906      |75,225 lb.|   ...  |  ...  |    ...   |  ...  |     ...
  Seychelles, 1906 |    ...   |   ...  |  ...  |    ...   |419,329|   129,590
                   |          |        |       |          | kilos.|     Rs.
_America_--        |          |        |       |          |       |
  New Orleans,     |    ...   |   ...  |  ...  |    ...   |  ...  |    £55,534
    1906           |          |        |       |          |       |
  Perambuco, 1906  |    ...   |   ...  |  ...  |    ...   | 3,582 |1,087,797,150
                   |          |        |       |          |  tons.|     rei
  United States,   |44,110,949|   ...  |  ...  |$1,042,185|  ...  |     ...
    1905           |    lb.   |        |       |          |       |
                   |          |        |       |          |       |
_Asia_--           |          |        |       |          |       |
  Japan, 1906      |    ...   |   ...  |  ...  |    ...   |  ...  |   £83,877
  Smyrna, 1906     |    ...   |   ...  |  ...  |    ...   |  322  |     ...
                   |          |        |       |          | tons. |
___________________|__________|________|_______|__________|_______|_____________

FOOTNOTES:

[13] Including soap powder and soap stock.

[14] Including soap powder and soap stock.



APPENDIX A.

COMPARISON OF DEGREES, TWADDELL AND BAUMÉ, WITH ACTUAL DENSITIES.


 _______________________________________________
|     |      |          |     |      |          |
| Tw. |   B. | Density. | Tw. |   B. | Density. |
|_____|______|__________|_____|______|__________|
|     |      |          |     |      |          |
|   0 |    0 |   1.000  |  44 | 26.0 |   1.220  |
|   1 |  0.7 |   1.005  |  45 | 26.4 |   1.225  |
|   2 |  1.4 |   1.010  |  46 | 26.9 |   1.230  |
|   3 |  2.1 |   1.015  |  47 | 27.4 |   1.235  |
|   4 |  2.7 |   1.020  |  48 | 27.9 |   1.240  |
|   5 |  3.4 |   1.025  |  49 | 28.4 |   1.245  |
|   6 |  4.1 |   1.030  |  50 | 28.8 |   1.250  |
|   7 |  4.7 |   1.035  |  51 | 29.3 |   1.255  |
|   8 |  5.4 |   1.040  |  52 | 29.7 |   1.260  |
|   9 |  6.0 |   1.045  |  53 | 30.2 |   1.265  |
|  10 |  6.7 |   1.050  |  54 | 30.6 |   1.270  |
|  11 |  7.4 |   1.055  |  55 | 31.1 |   1.275  |
|  12 |  8.0 |   1.060  |  56 | 31.5 |   1.280  |
|  13 |  8.7 |   1.065  |  57 | 32.0 |   1.285  |
|  14 |  9.4 |   1.070  |  58 | 32.4 |   1.290  |
|  15 | 10.0 |   1.075  |  59 | 32.8 |   1.295  |
|  16 | 10.6 |   1.080  |  60 | 33.3 |   1.300  |
|  17 | 11.2 |   1.085  |  61 | 33.7 |   1.305  |
|  18 | 11.9 |   1.090  |  62 | 34.2 |   1.310  |
|  19 | 12.4 |   1.095  |  63 | 34.6 |   1.315  |
|  20 | 13.0 |   1.100  |  64 | 35.0 |   1.320  |
|  21 | 13.6 |   1.105  |  65 | 35.4 |   1.325  |
|  22 | 14.2 |   1.110  |  66 | 35.8 |   1.330  |
|  23 | 14.9 |   1.115  |  67 | 36.2 |   1.335  |
|  24 | 15.4 |   1.120  |  68 | 36.6 |   1.340  |
|  25 | 16.0 |   1.125  |  69 | 37.0 |   1.345  |
|  26 | 16.5 |   1.130  |  70 | 37.4 |   1.350  |
|  27 | 17.1 |   1.135  |  71 | 37.8 |   1.355  |
|  28 | 17.7 |   1.140  |  72 | 38.2 |   1.360  |
|  29 | 18.3 |   1.145  |  73 | 38.6 |   1.365  |
|  30 | 18.8 |   1.150  |  74 | 39.0 |   1.370  |
|  31 | 19.3 |   1.155  |  75 | 39.4 |   1.375  |
|  32 | 19.8 |   1.160  |  76 | 39.8 |   1.380  |
|  33 | 20.3 |   1.165  |  77 | 40.1 |   1.385  |
|  34 | 20.9 |   1.170  |  78 | 40.5 |   1.390  |
|  35 | 21.4 |   1.175  |  79 | 40.8 |   1.395  |
|  36 | 22.0 |   1.180  |  80 | 41.2 |   1.400  |
|  37 | 22.5 |   1.185  |  81 | 41.6 |   1.405  |
|  38 | 23.0 |   1.190  |  82 | 42.0 |   1.410  |
|  39 | 23.5 |   1.195  |  83 | 42.3 |   1.415  |
|  40 | 24.0 |   1.200  |  84 | 42.7 |   1.420  |
|  41 | 24.5 |   1.205  |  85 | 43.1 |   1.425  |
|  42 | 25.0 |   1.210  |  86 | 43.4 |   1.430  |
|  43 | 25.5 |   1.215  |  87 | 48.8 |   1.435  |
|_____|______|__________|_____|______|__________|

 _______________________________________________
|     |      |          |     |      |          |
| Tw. |   B. | Density. | Tw. |   B. | Density. |
|_____|______|__________|_____|______|__________|
|     |      |          |     |      |          |
|  88 | 44.1 |   1.440  | 131 | 57.1 |   1.655  |
|  89 | 44.4 |   1.445  | 132 | 57.4 |   1.660  |
|  90 | 44.8 |   1.450  | 133 | 57.7 |   1.665  |
|  91 | 45.1 |   1.455  | 134 | 57.9 |   1.670  |
|  92 | 45.4 |   1.460  | 135 | 58.2 |   1.675  |
|  93 | 45.8 |   1.465  | 136 | 58.4 |   1.680  |
|  94 | 46.1 |   1.470  | 137 | 58.7 |   1.685  |
|  95 | 46.4 |   1.475  | 138 | 58.9 |   1.690  |
|  96 | 46.8 |   1.480  | 139 | 59.2 |   1.695  |
|  97 | 47.1 |   1.485  | 140 | 59.5 |   1.700  |
|  98 | 47.4 |   1.490  | 141 | 59.7 |   1.705  |
|  99 | 47.8 |   1.495  | 142 | 60.0 |   1.710  |
| 100 | 48.1 |   1.500  | 143 | 60.2 |   1.715  |
| 101 | 48.4 |   1.505  | 144 | 60.4 |   1.720  |
| 102 | 48.7 |   1.510  | 145 | 60.6 |   1.725  |
| 103 | 49.0 |   1.515  | 146 | 60.9 |   1.730  |
| 104 | 49.4 |   1.520  | 147 | 61.1 |   1.735  |
| 105 | 49.7 |   1.525  | 148 | 61.4 |   1.740  |
| 106 | 50.0 |   1.530  | 149 | 61.6 |   1.745  |
| 107 | 50.3 |   1.535  | 150 | 61.8 |   1.750  |
| 108 | 50.6 |   1.540  | 151 | 62.1 |   1.755  |
| 109 | 50.9 |   1.545  | 152 | 62.3 |   1.760  |
| 110 | 51.2 |   1.550  | 153 | 62.5 |   1.765  |
| 111 | 51.5 |   1.555  | 154 | 62.8 |   1.770  |
| 112 | 51.8 |   1.560  | 155 | 63.0 |   1.775  |
| 113 | 52.1 |   1.565  | 156 | 63.2 |   1.780  |
| 114 | 52.4 |   1.570  | 157 | 63.5 |   1.785  |
| 115 | 52.7 |   1.575  | 158 | 63.7 |   1.790  |
| 116 | 53.0 |   1.580  | 159 | 64.0 |   1.795  |
| 117 | 53.3 |   1.585  | 160 | 64.2 |   1.800  |
| 118 | 53.6 |   1.590  | 161 | 64.4 |   1.805  |
| 119 | 53.9 |   1.595  | 162 | 64.6 |   1.810  |
| 120 | 54.1 |   1.600  | 163 | 64.8 |   1.815  |
| 121 | 54.4 |   1.605  | 164 | 65.0 |   1.820  |
| 122 | 54.7 |   1.610  | 165 | 65.2 |   1.825  |
| 123 | 55.0 |   1.615  | 166 | 65.5 |   1.830  |
| 124 | 55.2 |   1.620  | 167 | 65.7 |   1.835  |
| 125 | 55.5 |   1.625  | 168 | 65.9 |   1.840  |
| 126 | 55.8 |   1.630  | 169 | 66.1 |   1.845  |
| 127 | 56.0 |   1.635  | 170 | 66.3 |   1.850  |
| 128 | 56.3 |   1.640  | 171 | 66.5 |   1.855  |
| 129 | 56.6 |   1.645  | 172 | 66.7 |   1.860  |
| 130 | 56.9 |   1.650  | 173 | 67.0 |   1.865  |
|_____|______|__________|_____|______|__________|

(From _The Oil and Colour Trades Journal_ Diary.)



APPENDIX B.

COMPARISON OF DIFFERENT THERMOMETRIC SCALES.


 _______________________________________________________________
|       |       |       |       |       |       |       |       |
| Cent. | Fahr. | Cent. | Fahr. | Cent. | Fahr. | Cent. | Fahr. |
|_______|_______|_______|_______|_______|_______|_______|_______|
|       |       |       |       |       |       |       |       |
|   -40 | -40   |     2 |  35.6 |    44 | 111.2 |    86 | 186.8 |
|    39 |  38.2 |     3 |  87.4 |    45 | 113   |    87 | 188.6 |
|    38 |  36.4 |     4 |  39.2 |    46 | 114.8 |    88 | 190.4 |
|    37 |  34.6 |     5 |  41   |    47 | 116.6 |    89 | 192.2 |
|    36 |  32.8 |     6 |  42.8 |    48 | 118.4 |    90 | 194   |
|    35 |  31   |     7 |  44.6 |    49 | 120.2 |    91 | 195.8 |
|    34 |  29.2 |     8 |  46.4 |    50 | 122   |    92 | 197.6 |
|    33 |  27.4 |     9 |  48.2 |    51 | 123.8 |    93 | 199.4 |
|    32 |  25.6 |    10 |  50   |    52 | 125.6 |    94 | 201.2 |
|    31 |  23.8 |    11 |  51.8 |    53 | 127.4 |    95 | 203   |
|    30 |  22   |    12 |  58.6 |    54 | 129.2 |    96 | 204.8 |
|    29 |  20.2 |    13 |  55.4 |    55 | 131   |    97 | 206.6 |
|    28 |  18.4 |    14 |  57.2 |    56 | 132.8 |    98 | 208.4 |
|    27 |  16.6 |    15 |  59   |    57 | 134.6 |    99 | 210.2 |
|    26 |  14.8 |    16 |  60.8 |    58 | 136.4 |   100 | 212   |
|    25 |  13   |    17 |  62.6 |    59 | 138.2 |   101 | 213.8 |
|    24 |  11.2 |    18 |  64.4 |    60 | 140   |   102 | 215.6 |
|    23 |   9.4 |    19 |  66.2 |    61 | 141.8 |  +103 |+217.4 |
|    22 |   7.6 |    20 |  68   |    62 | 143.6 |   104 | 219.2 |
|    21 |   5.8 |    21 |  69.8 |    63 | 145.4 |   105 | 221   |
|    20 |   4   |    22 |  71.6 |    64 | 147.2 |   106 | 222.8 |
|    19 |   2.2 |    23 |  73.4 |    65 | 149   |   107 | 224.6 |
|    18 |   0.4 |    24 |  75.2 |    66 | 150.8 |   108 | 226.4 |
|    17 |  +1.4 |    25 |  77   |    67 | 152.6 |   109 | 228.2 |
|    16 |   3.2 |    26 |  78.8 |   +68 |+154.4 |  +110 |+230   |
|    15 |   5   |    27 |  80.6 |    69 | 156.2 |   111 | 231.8 |
|    14 |   6.8 |    28 |  82.4 |    70 | 158   |   112 | 283.6 |
|    13 |   8.6 |    29 |  84.2 |    71 | 159.8 |   113 | 235.4 |
|    12 |  10.4 |    30 |  86   |    72 | 161.6 |   114 | 237.2 |
|    11 |  12.2 |    31 |  87.8 |    73 | 163.4 |   115 | 239   |
|    10 |  14   |   +32 | +89.6 |    74 | 165.2 |  +116 |+240.8 |
|     9 |  15.8 |    33 |  91.4 |    75 | 167   |   117 | 242.6 |
|     8 |  17.6 |    34 |  93.2 |    76 | 168.8 |   118 | 244.4 |
|     7 |  19.4 |    35 |  95   |    77 | 170.6 |   119 | 246.2 |
|     6 |  21.2 |    36 |  96.8 |    78 | 172.4 |   120 | 248   |
|     5 |  23   |    37 |  98.6 |    79 | 174.2 |   121 | 249.8 |
|    -4 |  24.8 |    49 | 100.4 |    80 | 176   |  +122 |+251.6 |
|     3 |  26.6 |    39 | 102.2 |    81 | 177.8 |   123 | 253.4 |
|     2 |  28.4 |    40 | 104   |    82 | 179.6 |   124 | 255.2 |
|     1 |  30.2 |    41 | 105.8 |    83 | 181.4 |   125 | 257   |
|     0 |  32   |    42 | 107.6 |    84 | 183.2 |   126 | 258.8 |
|    +1 |  33.8 |    43 | 109.4 |    85 | 185   |   127 | 260.6 |
|_______|_______|_______|_______|_______|_______|_______|_______|

(From _Soaps_, by G. H. Hurst, published by Scott, Greenwood & Son.)



APPENDIX C.

TABLE OF THE SPECIFIC GRAVITIES OF SOLUTIONS OF CAUSTIC SODA.


 _________________________________________________________________________
|           |          |                   |                              |
|           |          |   Per cent. by    | Lb. of actual NaOH contained |
|           |          |   weight of       | in 1 gallon of lye made from |
|           |          |                   | commercial caustic of        |
|  Degrees  | Specific |___________________|______________________________|
| Twaddell. | gravity. |          |        |         |         |          |
|           |          | Na_{2}O. |  NaOH. |  77 per |  74 per |  70 per  |
|           |          |          |        |   cent. |   cent. |   cent.  |
|___________|__________|__________|________|_________|_________|__________|
|           |          |          |        |         |         |          |
|     1     |   1.005  |   0.368  |  0.474 |  0.048  |  0.046  |   0.043  |
|     2     |   1.010  |   0.742  |  0.957 |  0.097  |  0.092  |   0.087  |
|     3     |   1.015  |   1.114  |  1.436 |  0.146  |  0.131  |   0.129  |
|     4     |   1.020  |   1.480  |  1.909 |  0.194  |  0.185  |   0.180  |
|     5     |   1.025  |   1.834  |  2.365 |  0.243  |  0.231  |   0.219  |
|     6     |   1.030  |   2.194  |  2.830 |  0.291  |  0.278  |   0.262  |
|     7     |   1.035  |   2.521  |  3.252 |  0.335  |  0.320  |   0.303  |
|     8     |   1.040  |   2.964  |  3.746 |  0.389  |  0.371  |   0.350  |
|     9     |   1.045  |   3.244  |  4.184 |  0.438  |  0.417  |   0.393  |
|    10     |   1.050  |   3.590  |  4.631 |  0.486  |  0.461  |   0.438  |
|    11     |   1.055  |   3.943  |  5.086 |  0.536  |  0.510  |   0.483  |
|    12     |   1.060  |   4.292  |  5.536 |  0.586  |  0.558  |   0.528  |
|    13     |   1.065  |   4.638  |  5.982 |  0.636  |  0.607  |   0.573  |
|    14     |   1.070  |   4.972  |  6.413 |  0.680  |  0.653  |   0.617  |
|    15     |   1.075  |   5.311  |  6.911 |  0.742  |  0.707  |   0.668  |
|    16     |   1.080  |   5.648  |  7.285 |  0.786  |  0.749  |   0.709  |
|    17     |   1.085  |   5.981  |  7.715 |  0.836  |  0.798  |   0.755  |
|    18     |   1.090  |   6.311  |  8.140 |  0.886  |  0.845  |   0.800  |
|    19     |   1.095  |   6.639  |  8.564 |  0.937  |  0.894  |   0.846  |
|    20     |   1.100  |   6.954  |  8.970 |  0.986  |  0.941  |   0.890  |
|    21     |   1.105  |   7.276  |  9.386 |  1.037  |  0.989  |   0.938  |
|    22     |   1.110  |   7.594  |  9.796 |  1.087  |  1.037  |   0.981  |
|    23     |   1.115  |   7.910  | 10.203 |  1.137  |  1.123  |   1.026  |
|    24     |   1.120  |   8.223  | 10.607 |  1.187  |  1.175  |   1.071  |
|    25     |   1.125  |   8.583  | 11.107 |  1.238  |  1.181  |   1.117  |
|    26     |   1.130  |   8.893  | 11.471 |  1.296  |  1.237  |   1.170  |
|    27     |   1.135  |   9.251  | 11.933 |  1.354  |  1.292  |   1.122  |
|    28     |   1.140  |   9.614  | 12.401 |  1.413  |  1.350  |   1.277  |
|    29     |   1.145  |   9.965  | 12.844 |  1.470  |  1.413  |   1.337  |
|    30     |   1.150  |  10.313  | 13.303 |  1.529  |  1.460  |   1.381  |
|    31     |   1.155  |  10.666  | 13.859 |  1.600  |  1.528  |   1.445  |
|    32     |   1.160  |  11.008  | 14.190 |  1.646  |  1.541  |   1.456  |
|    33     |   1.165  |  11.347  | 14.637 |  1.705  |  1.627  |   1.539  |
|    34     |   1.170  |  11.691  | 15.081 |  1.764  |  1.684  |   1.593  |
|    35     |   1.175  |  12.025  | 15.512 |  1.822  |  1.739  |   1.645  |
|    36     |   1.180  |  12.356  | 16.139 |  1.904  |  1.817  |   1.719  |
|    37     |   1.185  |  12.692  | 16.372 |  1.942  |  1.853  |   1.753  |
|    38     |   1.190  |  13.016  | 16.794 |  1.998  |  1.887  |   1.804  |
|    39     |   1.195  |  13.339  | 17.203 |  2.055  |  1.962  |   1.856  |
|    40     |   1.200  |  13.660  | 17.629 |  2.122  |  2.026  |   1.916  |
|    41     |   1.205  |  14.058  | 18.133 |  2.185  |  2.085  |   1.973  |
|    42     |   1.210  |  14.438  | 18.618 |  2.252  |  2.147  |   2.033  |
|    43     |   1.215  |  14.823  | 19.121 |  2.323  |  2.221  |   2.097  |
|    44     |   1.220  |  15.124  | 19.613 |  2.392  |  2.280  |   2.161  |
|    45     |   1.225  |  15.502  | 19.997 |  2.444  |  2.338  |   2.206  |
|    46     |   1.230  |  15.959  | 20.586 |  2.562  |  2.417  |   2.285  |
|    47     |   1.235  |  16.299  | 20.996 |  2.593  |  2.475  |   2.341  |
|    48     |   1.240  |  16.692  | 21.532 |  2.669  |  2.548  |   2.410  |
|___________|__________|__________|________|_________|_________|__________|

 _________________________________________________________________________
|           |          |                   |                              |
|           |          |   Per cent. by    | Lb. of actual NaOH contained |
|           |          |   weight of       | in 1 gallon of lye made from |
|           |          |                   | commercial caustic of        |
|  Degrees  | Specific |___________________|______________________________|
| Twaddell. | gravity. |          |        |         |         |          |
|           |          | Na_{2}O. |  NaOH. |  77 per |  74 per |  70 per  |
|           |          |          |        |   cent. |   cent. |   cent.  |
|___________|__________|__________|________|_________|_________|__________|
|           |          |          |        |         |         |          |
|    49     |   1.245  |  17.060  | 22.008 |  2.739  |  2.615  |   2.474  |
|    50     |   1.250  |  17.424  | 22.476 |  2.809  |  2.681  |   2.536  |
|    51     |   1.255  |  17.800  | 22.962 |  2.881  |  2.750  |   2.602  |
|    52     |   1.260  |  18.166  | 23.433 |  2.952  |  2.818  |   2.666  |
|    53     |   1.265  |  18.529  | 23.901 |  3.020  |  2.886  |   2.730  |
|    54     |   1.270  |  18.897  | 24.376 |  3.095  |  2.955  |   2.795  |
|    55     |   1.275  |  19.255  | 24.858 |  3.171  |  3.027  |   2.863  |
|    56     |   1.280  |  19.609  | 25.295 |  3.237  |  3.090  |   2.932  |
|    57     |   1.285  |  19.961  | 25.750 |  3.308  |  3.158  |   2.988  |
|    58     |   1.290  |  20.318  | 26.210 |  3.381  |  3.227  |   3.053  |
|    59     |   1.295  |  20.655  | 26.658 |  3.452  |  3.364  |   3.117  |
|    60     |   1.300  |  21.156  | 27.110 |  3.524  |  3.394  |   3.182  |
|    61     |   1.305  |  21.405  | 27.611 |  3.603  |  3.439  |   3.253  |
|    62     |   1.310  |  21.785  | 28.105 |  3.682  |  3.514  |   3.224  |
|    63     |   1.315  |  22.168  | 28.595 |  3.760  |  3.593  |   3.395  |
|    64     |   1.320  |  22.556  | 29.161 |  3.849  |  3.674  |   3.475  |
|    65     |   1.325  |  22.926  | 29.574 |  3.919  |  3.742  |   3.539  |
|    66     |   1.330  |  23.310  | 30.058 |  3.997  |  3.816  |   3.610  |
|    67     |   1.335  |  23.670  | 30.535 |  4.072  |  3.891  |   3.681  |
|    68     |   1.340  |  24.046  | 31.018 |  4.156  |  3.967  |   3.754  |
|    69     |   1.345  |  24.410  | 31.490 |  4.232  |  4.042  |   3.824  |
|    70     |   1.350  |  24.765  | 31.948 |  4.312  |  4.116  |   3.894  |
|    71     |   1.355  |  25.152  | 32.446 |  4.396  |  4.196  |   3.970  |
|    72     |   1.360  |  25.526  | 32.930 |  4.478  |  4.274  |   4.043  |
|    73     |   1.365  |  25.901  | 33.415 |  4.561  |  4.354  |   4.109  |
|    74     |   1.370  |  26.285  | 33.905 |  4.645  |  4.434  |   4.194  |
|    75     |   1.375  |  26.650  | 34.382 |  4.728  |  4.513  |   4.269  |
|    76     |   1.380  |  27.021  | 34.855 |  4.810  |  4.592  |   4.344  |
|    77     |   1.385  |  27.385  | 35.328 |  4.893  |  4.670  |   4.418  |
|    78     |   1.390  |  27.745  | 35.795 |  4.975  |  4.794  |   4.493  |
|    79     |   1.395  |  28.110  | 36.258 |  5.058  |  4.828  |   4.567  |
|    80     |   1.400  |  28.465  | 36.720 |  5.141  |  4.907  |   4.642  |
|    81     |   1.405  |  28.836  | 37.203 |  5.227  |  4.989  |   4.720  |
|    82     |   1.410  |  29.203  | 37.674 |  5.312  |  5.071  |   4.797  |
|    83     |   1.415  |  29.570  | 38.146 |  5.397  |  5.135  |   4.873  |
|    84     |   1.420  |  29.930  | 38.610 |  5.482  |  5.233  |   4.950  |
|    85     |   1.425  |  30.285  | 39.071 |  5.567  |  5.314  |   5.027  |
|    86     |   1.430  |  30.645  | 39.530 |  5.653  |  5.396  |   5.104  |
|    87     |   1.435  |  30.995  | 39.986 |  5.738  |  5.467  |   5.181  |
|    88     |   1.440  |  31.349  | 40.435 |  5.823  |  5.558  |   5.258  |
|    89     |   1.445  |  31.700  | 40.882 |  5.908  |  5.640  |   5.335  |
|    90     |   1.450  |  32.043  | 41.335 |  5.923  |  5.721  |   5.412  |
|    91     |   1.455  |  32.460  | 41.875 |  6.093  |  5.816  |   5.502  |
|    92     |   1.460  |  32.870  | 42.400 |  6.191  |  5.909  |   5.608  |
|    93     |   1.465  |  33.283  | 42.935 |  6.290  |  6.004  |   5.679  |
|    94     |   1.470  |  33.695  | 43.467 |  6.389  |  6.009  |   5.769  |
|    95     |   1.475  |  34.092  | 43.980 |  6.487  |  6.193  |   5.856  |
|    96     |   1.480  |  34.500  | 44.505 |  6.586  |  6.287  |   5.948  |
|    97     |   1.485  |  34.899  | 45.013 |  6.685  |  6.381  |   6.035  |
|    98     |   1.490  |  35.245  | 45.530 |  6.784  |  6.476  |   6.126  |
|    99     |   1.495  |  35.691  | 46.041 |  6.884  |  6.571  |   6.216  |
|   100     |   1.500  |  36.081  | 46.545 |  6.982  |  6.665  |   6.303  |
|___________|__________|__________|________|_________|_________|__________|

(From _Soaps_, by G. H. Hurst, published by Scott, Greenwood & Son.)



APPENDIX D.

TABLE OF STRENGTH OF CAUSTIC POTASH SOLUTIONS AT 60° F.


 _______________________________________________
|          |           |           |            |
| Specific |  Degrees  | Per cent. | Lb. of KOH |
| gravity. | Twaddell. |    KOH.   | per gal.   |
|__________|___________|___________|____________|
|          |           |           |            |
|   1.060  |     12    |    5.59   |    0.59    |
|   1.110  |     22    |   11.31   |    1.25    |
|   1.150  |     30    |   15.48   |    1.77    |
|   1.190  |     38    |   19.29   |    2.21    |
|   1.230  |     46    |   23.22   |    2.84    |
|   1.280  |     56    |   27.87   |    3.56    |
|   1.330  |     66    |   31.32   |    4.16    |
|   1.360  |     72    |   35.01   |    4.76    |
|   1.390  |     78    |   38.59   |    5.36    |
|   1.420  |     84    |   40.97   |    5.81    |
|   1.440  |     88    |   43.83   |    6.31    |
|   1.470  |     94    |   47.16   |    6.93    |
|   1.520  |    104    |   51.09   |    7.76    |
|   1.600  |    112    |   55.62   |    8.89    |
|   1.680  |    136    |   60.98   |   10.24    |
|   1.780  |    156    |   67.65   |   12.04    |
|   1.880  |    176    |   75.74   |   14.23    |
|   2.000  |    200    |   86.22   |   17.24    |
|__________|___________|___________|____________|

(From _Soaps_, by G. H. Hurst, published by Scott, Greenwood & Son.)


THE END.



INDEX.


A.

Acetic Acid, 10

Acid, Acetic, 10

---- Arachidic, 10

---- Behenic, 10

---- Butyric, 10

---- Capric, 10

---- Caproic, 10

---- Caprylic, 10

---- Carnaubic, 10

---- Cerotic, 10

---- Daturic, 10

---- Doeglic, 11

---- Elæomargaric, 12

---- Elæostearic, 12

---- Erucic, 11

---- Ficocerylic, 10

---- Hyænic, 10

---- Hypogæic, 11

---- Isolinolenic, 12

---- Isovaleric, 10

---- Jecoric, 12

---- Lauric, 10

---- Lignoceric, 10

---- Linolenic, 12

---- Linolic, 12

---- Margaric, 10

---- Medullic, 10

---- Melissic, 10

---- Moringic, 11

---- Myristic, 10

---- Oleic, 11

---- Palmitic, 10

---- Physetoleic, 11

---- Pisangcerylic, 10

---- Psyllostearylic, 10

---- Rapic, 11

---- Ricinoleic, 13

---- Saponification, 19-21

---- Stearic, 10

---- Tariric, 12

---- Telfairic, 12

---- Theobromic, 10

---- Tiglic, 11

---- value, 118, 128

Acids, Classification of fatty, 10

---- Fatty, 9-13

---- ---- Combination with Alkali, 45, 46

Acids, Fatty, Preparation by acid process, 19-21

----    ----    ---- by ferment process, 16

----    ----    ---- by Twitchell's process, 20

---- Saturated fatty, 11

---- Unsaturated fatty, 11

Albumen in soap, 90

Alcohols, Estimation of, 128

Aldehydes, Estimation of, 129

Alkali, Caustic and carbonated, 38, 39, 123-126

Alkali in soap, Determination of, 131, 132

Amyl salicylate, 107

Andiroba oil, 32

Animal charcoal, 115

---- fats, Treatment of, 43

Anise (star) oil, 96

Anisic aldehyde, 108

Arachidic acid, 10

Arachis oil, 28

Artificial perfumes, 107-110

Ash, Soda, 39, 124, 125

Aspic oil, 96

Aqueous saponification, 14

Aubépine, 108


B.

Bacteria, Decomposition of fats by, 18

Baobab-seed oil, 36

Bar soap, 54, 55

Barring soap, 68

Bay oil, 97

Behenic acid, 10

Benzyl acetate, 108

Bergamot oil, 97

---- ---- (artificial), 109

Biniodide soaps, 87

Birch-tar soap, 88

Bitter almond oil, 97

Bleaching palm oil, 41

---- rosin, 43

Boiling-on-strength, 51

Bois de Rose Femelle oil, 99

Bone-fat, 30

---- ---- treatment of, 43

Borax in soap, 88

Boric acid in soap, 88

Boric acid in soap, Determination of, 135

Borneo tallow, 32

Brine, 39

Bromine absorption of oils and fats, 122

Brown Windsor soap, 78, 98

Butter goa, 33

---- kokum, 33

---- shea, 31

Butyric acid, 10

Butyrin, 8


C.

Calico-printer's soap, 93

Cananga oil, 98

Candle-nut oil, 33

Capric acid, 10

Caprin, 8

Caproic acid, 10

Caproin, 8

Caprylic acid, 10

Caprylin, 8

Carapa oil, 32

Caraway oil, 98

Carbolic acid in soap, Determination of, 134

Carbolic soap, 88

Carbonate potash, 39, 125, 126

---- soda, 39, 124, 125

Carnaubic acid, 10

Cassia oil, 98

Castor oil, 30

Caustic potash, 39, 123

---- soda, 39, 123

Cayenne linaloe oil, 99

Cedarwood oil, 98

Cerotic acid, 10

Charcoal, Animal, 115

Chinese vegetable tallow, 31

Cholesterol in unsaponified matter, 120

Cinnamon oil, 98

Citral, 108

Citronella oil, 99

Citronellal, 108

Cleansing soap, 60, 61

Close-piling soap, 71

Clove oil, 99

Coal tar soaps, 88

Cocoa-nut oil, 25, 26

Cohune-nut oil, 34

Cold process soap-making, 46, 47

Colouring soap, 66, 80, 82

Compressing soap, 83, 85

Concrete orris oil, 100

Constitution of oils and fats, 6, 7

Conversion of oleic acid into solid acids, 11, 12

Cooling soap, 74, 76

Coprah oil, 25, 26

Cotton-seed oil, 27, 42

---- ---- Refining, 42

---- soapstock, 40

---- stearine, 28

Coumarin, 108

Crude glycerine, 113, 136-139

Crutching soap, 63

Curcas oil, 33

Curd mottled soap, 52, 53

Curd soaps, 52

Cutting and stamping toilet soap, 85


D.

Daturic acid, 10

Decolorisation, Glycerine, 115

Decomposition of fats by bacteria, 18

Detergent action of soap, 4, 5

Diglycerides, 7

Dika fat, 36

Disinfectant soaps, 66

Distearine, 7

Distillation, glycerine, 114

Distilled glycerine, 114

Doeglic acid, 11

Double distilled glycerine, 115

Dregs in fats and oils, Determination of, 120, 121

Drying soap, 71, 78-80

Dynamite glycerine, 115


E.

Elaidin reaction, 12

Electrical production of soap, 59

Elæomargaric acid, 12

Elæostearic acid, 12

Enzymes, Action of, 15-18

Erucic acid, 11

Essential oils, 96-107

---- ---- Examination of, 127-130

Ester value, 119, 128

Ether soap, 90

Eucalyptus oil, 100

Evaporation to crude glycerine, 112, 113


F.

Fat, Bone, 30

---- Dika, 36

---- Maripa, 34

---- Marrow, 30

---- Niam, 34

---- Tangkallah, 37

---- Treatment of bone, 43

Fats, Decomposition by bacteria of, 18

---- Treatment of animal, 43

---- Waste, 30

Fats and oils, Determination of acid value of, 118

---- ---- ---- of bromine absorption of, 122

---- ---- ---- of dregs, etc., in, 120, 121

---- ---- ---- of free acidity of, 117

---- ---- ---- of iodine absorption of, 121, 122

---- ---- ---- of saponification

---- ---- ---- equivalents of, 118

---- ---- ---- of saponification value, 118

---- ---- ---- of specific gravity of, 117 of titre of, 122, 123

---- ---- ---- of unsaponifiable matter in, 119

---- ---- ---- of water in, 120

---- ---- ---- Yield of glycerine from, 116

Fatty acids, 9-13, 31

---- ---- Classification of, 10

---- ---- Direct combination with alkali of, 45, 46

---- ---- in soap, Determination of, 131

---- ---- ---- Examination of, 133, 134

---- ---- Preparation by acid process, 19-21

---- ---- ---- by ferment process, 16

---- ---- ---- by Twitchell's process, 20

---- ---- Saturated, 11

---- ---- Unsaturated, 11

Fennel oil, 100

Ferment process for preparation of fatty acids, 16

Ferments, action of, 15-18

Ficocerylic acid, 10

Filling soap, 65

Fish oils, 30

"Fitting," 51

Floating soap, 90, 91

Fluorides in soap, 88

Formaldehyde soap, 88

Framing soap, 66

Free alkali in soap, Estimation of, 132

---- caustic in soap, Neutralising, 66

---- fat in soap, Determination of, 133

---- fatty acids, Determination of, 117


G.

Geraniol, 108

Geranium oils, 101

Geranium-sur-rose oil, 101

Ginger-grass oil, 101

Glycerides, 7, 8

Glycerine, Chemically pure, 115

---- Crude, 113, 136-139

---- decolorisation, 115

---- distillation, 114

---- Distilled, 114

---- dynamite, 115

---- in soap, Determination of, 134, 135

---- manufacture, 111-114

---- saponification, 116

---- soaps, 89

---- Yield of, from fats and oils, 116

Glycerol determination, acetin method, 136

---- ---- bichromate method, 137, 138

---- in lyes, Estimation of, 135

Goa-butter, 33

"Graining-out," 50

Grease, Animal, 30

---- Bone, 30

---- Kitchen, 30

---- Skin, 30

Guaiac wood oil, 101


H.

Halphen's reaction, 134

Heliotropin, 108

Hemp-seed oil, 29

Hyacinth, 108

Hyænic acid, 10

Hydrated soaps, 48, 49

Hydrolysis accelerated by heat and electricity, 14, 15

---- accelerated by use of chemical reagents,  19-23

---- accelerated with acid, 19, 21

---- Enzymic, 15-18

---- of oils and fats, 13-23

---- of soap, 3

Hypogæic acid, 11


I.

Ichthyol soap, 89

Inoy-kernel oil, 37

Iodine absorption of rose oil, 130

---- absorption of oils and fats, 121,122:

---- soap, 89

Ionone, 108

Isolinolenic acid, 12

Isovaleric acid, 10

Isovalerin, 8


J.

Jasmine, 109

Jecoric acid, 12


K.

Kananga oil, 98

Kapok oil, 32

"Kastilis," 88

Kokum butter, 33


L.

Lard, 25

Lauric acid, 10

Laurin, 8

Lavender oils, 101

Lemon-grass oil, 102

Lemon oil, 102

Lignoceric acid, 10

Lime oil, 102

---- saponification, 22

Linaloe oil, 102

Linalol, 109

Linalyl acetate, 109

Linolenic acid, 12

Linolic acid, 12

Linseed oil, 29

Lipase, 18

Liquoring of soaps, 64

Lyes, analysis of, 135

---- Determination of glycerol in, 135

---- Evaporation of, 112

---- Treatment of, 111, 112

Lysol soap, 89


M.

Mafura tallow, 35

Magnesia, Hydrolysis by, 22

Maize oil, 28

Margaric acid, 10

Margosa oil, 35

Marine animal oils, 30

---- soap, 49

Maripa fat, 34

Marjoram oil, 103

Medicated soaps, 86-90

Medullic acid, 10

Melissic acid, 10

Melting point, 130

Mercury soaps, 87

Milled toilet soaps, 78

Milling soap, 80, 81

---- soap-base, 54, 78

Mineral oil, saponifying, 58, 59

Mirbane oil or nitrobenzene, 109

Mixed glycerides, 8

Monoglycerides, 7

Monostearin, 7

Moringic acid, 11

Mottled soaps, 52, 53

---- ---- Pickling, 54

Moulds, Soap, 72, 85, 86

Mowrah-seed oil, 31

Musk (artificial), 109

Myristic acid, 8

Myristin, 8


N.

Naphthol soap, 89

Neroli Bigarade oil, 103

---- oil (artificial), 109

Neutralising free caustic in soap, 66, 80

Niam fat, 34

Nigre, 56

Nigres, Utilisation of, 56

Niobe oil or ethyl benzoate, 110

Nitrobenzene, 109


O.

Oeillet, 10

Oil, Andiroba, 32

---- Arachis, 28

---- Aspic (lavender spike), 96

---- Baobab-seed, 36

---- Bay, 97

---- Bergamot, 97

---- Bitter almond, 97

---- Bleaching palm, 41

---- Bois de Rose Femelle, 99

---- Cananga, 98

---- Candle-nut, 33

---- Carapa, 32

---- Caraway, 98

---- Cassia, 98

---- Castor, 30

---- Cayenne linaloe, 99

---- Cedarwood, 98

---- Cinnamon, 98

---- Citronella, 99

---- Clove, 99

---- Cocoa-nut, 25, 26

---- Cohune-nut, 34, 35

---- Concrete orris, 100

---- Coprah, 25, 26

---- Cotton-seed, 27, 42

---- Curcas, 33

---- Eucalyptus, 100

---- Fennel, 100

---- Geranium, 101

---- Ginger-grass, 101

---- Guaiac-wood, 101

---- Hemp-seed, 29

---- Inoy-kernel, 37

---- Kananga, 98

---- Kapok, 32

---- Lemon, 102

---- Lemon-grass, 102

---- Lime, 102

---- Linaloe, 102

---- Linseed, 29

---- Maize, 28

---- Margosa, 35

---- Marjoram, 103

---- Mowrah-seed, 31

---- Neroli Bigarade, 103

---- Olive, 26

---- Olive-kernel, 27

---- Orange, 163

---- Palm, 27, 41

---- Palm-nut, 26

---- Palmarosa, 103

---- Patchouli, 103

---- Peppermint, 103, 104

---- Persimmon-seed, 36

---- Peru-balsam, 104

---- Petit-grain, 104

---- Pongam, 35

---- Refining cotton-seed, 42

---- Rose, 105

---- Rosemary, 105

---- Safflower, 33, 34

---- Sandalwood, 105, 106

---- Saponifying mineral, 58, 59

---- Sassafras, 106

---- Sesame, 28, 29

---- Star-anise, 96

---- Sunflower, 29

---- Thyme, 106

---- Verbena, 106

---- Vetivert, 106-107

---- Wheat, 36

---- Wild mango, 36

---- Wintergreen, 107

---- Ylang-ylang, 107

Oils and fats, Constitution of, 6, 7

---- ---- Examination of, 117-123

---- ---- Hydrolysis of, 13-22

---- Fish and marine animal, 30

---- Lavender, 101

---- Refractive Index of, 122

---- treatment of vegetable, 43

Oleic acid, 11

---- ---- into solid acids, Conversion of, 11, 12

Olein, 8, 9, 31

---- Cocoa-nut, 31

---- Palm-nut, 31

Oleodidaturin, 8

Oleodipalmitin, 8

Oleodistearin, 8

Oleopaimitostearin, 8

Olive-kernel oil, 27

Olive oil, 26

Open-piling soap, 71

Optical rotation, 127

Orange oil, 103

Orchidée, 107

Orris oil, concrete, 100


P.

Palm oil, 27, 41

---- ---- Bleaching, 41

Palmarosa oil, 103

Palmitic acid, 10

Palmitin, 8

Palmitodistearin, 8

Palm-nut oil, 26

Pasting or saponification, 49

Patchouli oil, 103

Patent textile soaps, 94

Pearl-ash, Analysis of, 125, 126

Peppermint oil, 103, 104

Perfumer's soaps, 77, 78

Perfumes, Artificial and synthetic, 107-110

---- Soap, 95-110

Perfuming soaps, 94

Persimmon seed oil, 36

Peru-balsam oil, 104

Petit-grain oil, 104

Phenols, Determination of, 129

Physetoleic acid, 11

Phytosterol in unsaponifiable matter, 120

Pickling mottled soap, 54

Pisangcerylic acid, 10

Polishing soaps, 94

Pongam oil, 35

Potash, Carbonate, 39, 125, 126

---- Caustic, 89, 123

Potassium chloride, 126

---- Determination of, 126, 132

Powders, Soap, 94

Psyllostearylic acid, 10


R.

Rancidity, 18, 24

Rapic acid, 11

Refining cotton-seed oil, 42

Refractive index of oils and fats, 122

Remelted soaps, 77, 78

Resinate of soda, 43, 44

Ricinoleic acid, 13

Ricinolein, 8

Rose oil, 105

---- ---- (artificial), 110

Rosemary oil, 105

Rosin, 37, 38, 43, 44, 55

---- Bleaching, 43

---- Determination of, 133, 134

---- treatment, 43, 44


S.

Safflower oil, 33, 34

Safrol, 110

Salt, 39, 126

---- Determination of, 124, 125, 126, 132

Sandalwood oil, 105, 106

Santalol, 110

Saponification, 13-22, 49

---- accelerated by heat and electricity, 14, 15

---- accelerated by use of chemical reagents, 19, 23

---- accelerated with Twitchell's reagent, 20

---- Acid, 19, 21

---- Aqueous, 14

---- by ferment process, 20

---- equivalent, 118

---- Glycerine, 116

---- Lime, 22

---- under pressure, 47

---- value, 118, 128

Saponifying mineral oil, 58, 59

Sassafras oil, 106

Saturated acids, 11

Scouring soaps, 92, 93

Sesame oil, 28, 29

Settled soap, Treatment of, 60-76

Shaving soaps, 91

Shea butter, 31

Silicate of soda in soap, 65

Silicates of soda and potash, 127, 138

Silk scouring soaps, 93

---- dyer's soap, 93, 94

Slabbing soap, 68

Soap, Albumen in, 90

---- Analysis of, 130-35

---- Bar, 54, 55

---- Barring, 68

---- -base, Milling, 54, 78

---- Biniodide, 87

---- Birch-tar, 88

---- Borax, 88

---- Boric acid in, 88

---- ---- ---- ---- Determination, 135

---- Carbolic, 88

---- Classification of, 45

---- Cleansing, 60, 61

---- Coal-tar, 88

---- Cold process, 46, 47

---- Compressing, 83, 85

---- Cooling, 74-76

---- Crutching, 63

---- Curd, 52

---- Curd mottled, 53

---- Definition of, 1, 2

---- Detergent action of, 4, 5

---- Determination of carbolic acid in, 134

---- ---- of fatty acids in, 131

---- ---- of free alkali in, 132

---- ---- of free fat in, 133

---- ---- of glycerine in, 134, 135

---- ---- of total alkali in, 131

---- ---- of water in, 133

---- Drying, 71, 78-80

---- Electrical production of, 59

---- Ether, 90

---- Examination of fatty acids 133, 134

---- Filling, 65

---- Fluorides in, 90

---- formaldehyde, 88

---- frame, 66

---- framing, 66

---- from fatty acids, 45, 46

---- Glycerine, 89

---- Hydrated, 48, 49

---- Hydrolysis of, 3

---- Ichthyol, 89

---- Iodine, 89

---- Lysol, 89

---- Marine, 49

---- Milling, 80, 81

---- Monopole, 94

---- Mottled, 52, 53

---- moulds, 72, 85, 86

---- Naphthol, 89

---- Neutralising, colouring and perfuming, 66, 80, 82

---- Open and close piling, 71

---- perfumes, 95-110

---- Pickling mottled, 54

---- powders, 94

---- Properties of, 2

---- Salicylic acid, 88

---- Settling of, 55

---- Slabbing, 68

---- Soft, 41

---- Stamping, 71, 72, 85, 86

---- Sulphur, 89

---- Terebene, 90

---- Thymol, 90

---- Transparent, 57, 58

---- Treatment of settled, 60-76

---- Yellow household, 54, 55

Soap-making, 45-59

---- ---- Blue and grey mottled, 53

---- ---- "Boiling-on-strength," 51

---- ---- Cold process, 46, 47

---- ---- Combination of fatty acids with alkali, 45, 46

---- ---- Curd, 52

---- ---- Curd, Mottled, 53

---- ---- "Fitting," 51

---- ---- "Graining-out" or separation, 50

---- ---- Hydrated, 49

---- ---- "Pasting" or saponification, 49

---- ---- Soft, 48

---- ---- Transparent, 57, 58

---- ---- under pressure, 47

Soaps, Calico-printer's, 93

---- Disinfectant, 66

---- Floating, 90, 91

---- Liquoring of, 64, 65

---- Medicated, 86-90

---- Milled toilet, 78

---- Miscellaneous, 94

---- Perfumer's, 77, 78

---- Polishing, 94

---- Remelted, 77, 78

---- Scouring, 92

---- Shaving, 91

---- Silicating, 65

---- Silk dyer's, 93, 94

---- Textile, 91-94

---- Toilet, 77, 78

---- Woollen dyer's, 92

Soap-stock, 40

Soda ash, 39, 124, 125

---- ---- Caustic, 39, 125

---- Carbonate, 39, 124, 125

---- Caustic, 39, 123

---- Resinate, 43, 44

Soft soap-making, 48

Solidifying-point, 130

Specific gravity, Determination of, 117, 127

Stamping soap, 71, 72, 85, 86

Starch, Detection of, 121, 135

Steapsin, 18

Stearic acid, 10

Stearin, 8, 9

Stearine, Cotton-seed, 28

Stearodipalmitin, 8

Sulphides and sulphites, Determination of, 125

Sulphur soap, 89

Sunflower oil, 29

Superfatting material, 83

Synthetic perfumes, 107-110


T.

Table of caustic potash solutions, 151

---- of caustic soda solutions, 149, 150

---- of comparative densities, 147

---- of thermometric equivalents, 148

Tablet soap, 55

Talc, 65

Tallow, 24

---- Borneo, 32

---- Chinese vegetable, 31

---- Mafura, 35

Tangkallah fat, 37

Tariric acid, 12

Telfairic acid, 12

Terebene, 110

---- soap, 90

Terpineol, 110

Textile soaps, 91-94

---- ---- Patent, 94

Theobromic acid, 10

Thyme oil, 106

Thymol soap, 90

Tiglic acid, 11

Titre test, 122, 123

Toilet soaps, 77, 78

---- ---- Compressing, 83, 85

---- ---- Milled, 78

---- ---- Milling, 80, 81

---- ---- Stamping, 85, 86

Transparent soaps, 57, 58

Treatment of animal fats, 43

---- ---- bone fat, 43

---- ---- lyes, 111, 112

---- ---- rosin, 43

---- ---- settled soap, 60-76

---- ---- Vegetable oils, 43

Trèfle, 107

Triglycerides, 7, 8

Trilaurin, 9

Triolein, 9

Tripalmitin, 9

Tristearin, 7, 9

Twitchell's process, 22


U.

Unsaponifiable matter, Constitution of, 119, 120

---- ---- Determination of, 119

Unsaturated acids, 11

Utilisation of nigres, 56


V.

Vanillin, 110

Vegetable oils, Treatment of, 43

---- tallow, Chinese, 31

Verbena oil, 106

Vetivert oil, 106

Violet soap, 54

Volhard's method for chloride determination, 132


W.

Waste fats, 30

Water, 39

---- ---- in fats, Determination of, 120

---- ---- in soap, Determination of, 133

Wheat oil, 36

Wild mango oil, 36

Wintergreen oil, 107

Wool scouring soaps, 92

Woollen dyer's soap, 92


Y.

Ylang-ylang oil, 107


Z.

Zinc oxide, Hydrolysis by, 22

---- soap, 87

THE ABERDEEN UNIVERSITY PRESS LIMITED



          STEVENSON & HOWELL'S

          SPECIALITIES FOR

          Soapmakers & Wholesale Perfumers.


          ESSENTIAL OILS

          OF GUARANTEED PURITY.


          Almonds, Bay Leaves, Bergamot, Caraway,
          Cananga, Camomile, Cascarilla, Cassia,
          Cedar Wood, Cinnamon, Citronella, Cloves,
          Coriander, Eucalyptus Globulus, Fennel, Sweet,
          Geranium -- _Algerian_, _Bourbon_, _East Indian_,
          _French_, _Spanish_ & _Turkish_,
          Kuromoji, Lavender, Lemon, Lemon-Grass,
          Limes, Neroli, Myrbane, Orange Sweet & Bitter,
          Otto of Rose, Patchouli, Palmarosa, Pimento,
          Petit-Grain, Rosemary, Sandal Wood, Sage,
          Sassafras, Spearmint, Thyme, Wintergreen
          Ylang-Ylang., &c.


          TOILET SOAP PERFUMES

          FINEST QUALITY

          Almond, Bay Rum, Brown Windsor, Cologne,
          Florida, Frangipanni, Heliotrope, Hyacinth, Lilac,
          Lily of Valley, Oriental, Parisian, Walnut Leaf,
          Wood Violet, &c.


          ARTIFICIAL PERFUMES.

          Aubepine, Cuir de Russiè, Coumarin, Crategine,
          Heliotropine, Lilac, Musk, Nerolin, Terpineol,
          Vanillin, Yara-Yara, &c.

          SOAP COLOURS, Dark Blue, Rose Pink,
          Indian Brown, Carbolic Pink & Red, Manchester Yellow.
          &c. &c.

          _SPECIALITY_:--RELIABLE CHLORPHYL.

          STANDARD WORKS

          SOUTHWARK ST. LONDON. S. E.

          GLASGOW OFFICE         128, HOPE ST.



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                             TEXTILE

                          SOAPS AND OILS.

           Handbook on the Preparation, Properties and Analysis
           of the Soaps and Oils used in Textile Manufacturing,
                          Dyeing and Printing.

                                   BY
                         GEORGE H. HURST, F.C.S.,

           Author of "Soaps," "Lubricating Oils, Fats and Greases," etc.

                                CONTENTS.

              Methods of Making Soaps--Special Textile Soaps--Relation of Soap
              to Water for Industrial Purposes--Soap Analysis--Fat in
              Soap--Animal and Vegetable Oils and Fats--Vegetable Soap, Oils
              and Fats--Glycerine--Textile Oils.

          Price 5s. net (Post Free, 5s. 4d. Home; 5s. 6d. Abroad).

          Published by

          SCOTT, GREENWOOD & SON,
          8 BROADWAY, LUDGATE HILL, LONDON, E.C.



          WILLIAM TULLOCH & CO.,

          30 George Square, Glasgow,
          And at 9 Great Tower Street, London, E.C.,
          14 No. Corridor, Royal Exchange, Manchester.

          GLYCERINE,

          CRUDE, DYNAMITE, INDUSTRIAL, CHEMICALLY PURE.

          All Kinds of Chemicals for Soap and Explosives Makers.

          NITRATE OF LEAD, FARINAS, STARCHES, GUMS.

          TWITCHELL PROCESS OF
          GLYCERINE EXTRACTION.

          HIGHEST

          Degree of Decomposition.

          LOWEST

          Cost for Installation and Working.

          BEST

          Qualities of Fatty Acids, Glycerine, Stearine and Soap.

          For Samples and information, apply to

          WM. TULLOCH & CO.,

          30 GEORGE SQUARE, GLASGOW.
          General Representatives for United Kingdom and Colonies.

          SUDFELDT & CO., MELLE (HANOVER, GERMANY).

          JOSLIN SCHMIDT & CO.,

          CINCINNATI, OHIO, U.S.A.



          THE CHEMISTRY OF

          Essential Oils

          AND

          Artificial Perfumes.

          BY

          ERNEST J. PARRY, B.Sc. (Lond.), F.I.C., F.C.S.

          552 Pages. Second Edition, Revised and Enlarged. Demy 8vo. 1908.

     CONTENTS.

     Chapters I. ~The General Properties of Essential Oils.~ Physical
     Properties, Optical Properties, Table of Specific Gravities,
     Refractive Indices and Rotation.--II. ~Compounds occurring in
     Essential Oils.~ (I.) 1. TERPENES--Pinene, Camphene, Limonene,
     Dipentene, Fenchene, Sylvestrene, Carvestrene, Phellandrene,
     Terpinolene, Terpinene and Thujene. 2.
     SESQUITERPENES--Cadinene, Caryophellene, Cedrene, Clovene,
     Humulene, Ledene, Patchoulene, and Sesquiterpene from Oils of
     Cannabis Indica, Table, b.p., sp.-gr., opt. Rot., etc., of
     same. (II.) THE CAMPHOR SERIES--Borneol, Isoborneol, Camphor,
     Fenchyl Alcohol, Fenchone, Thujyl Alcohol, Thujone, Terpineol,
     Cineol, etc., etc. (III.) THE GERANIOL AND CITRONELLOL
     GROUP--Coriandrol, Nerolol, Rhodinol, Geraniol, Linalol,
     Citrenellol, etc., Table, b.p., sp.-gr., Ref. Index, etc. (IV.)
     BENZENE COMPOUNDS--Cymene, Phenols and their Derivatives,
     Phenols with Nine Carbon Atoms, Phenols with Ten Carbon Atoms,
     Alcohols, Aldehydes, Ketones, Acids, etc. (V.) ALIPHATIC
     COMPOUNDS--Alcohols, Acids, Aldehydes, Sulphur Compounds,
     etc.--III. ~The Preparation of Essential Oils.~ Expression,
     Distillation, Extraction, Table of Percentages.--IV. ~The
     Analysis of Essential Oils.~ Specific Gravity, Sprengel Tube
     Method, Optical Methods, Melting and Solidifying Points,
     Boiling Point and Distillation, Quantitative Estimations of
     Constituents, the Determination of Free Alcohols, Absorption
     Processes.--V. ~Systematic Study of the Essential Oils.~ Oils of
     the Gymnosperms, Tabulated Angiosperms. (I.) WOOD OILS.--Cedar
     Oils, Oils of Turpentine, American Turpentine, French Oil of
     Turpentine, German, Russian, and Swedish ditto, Table of
     Activities of same, Juniper Wood Oil. (II.) FRUIT
     OILS.--Juniper Berry Oil, Fir Cone Oils. (III.) LEAF
     OILS.--Thuja Oil, Oil of Savin, Cedar Leaf Oil, Pine Needle
     Oil, Cypress Leaf Oil, Table of Pine Oils (after Schimmel).
     OILS OF THE ANGIOSPERMS--(I.) MONOCOTYLEDONS. (II.)
     DICOTYLEDONS: (_a_) MONOCHLAMYDEÆ--(_b_) GAMOPETALÆ--(_c_)
     POLYPETALÆ--VI. ~Terpeneless Oils.~ Terpeneless Oil of Lemon,
     Tables of sp.-gr. and Rotn. of several Terpeneless Oils,
     Terpeneless Oil of Orange, Ditto of Caraway, of Lavender, Table
     of sp.-gr. and Rotn. of Commercial Samples of Oils.--VII. ~The
     Chemistry of Artificial Perfumes.~ Vanillin, Coumarin,
     Heliotropin, Aubepine or Hawthorn, Ionone, Specification of
     Patents for Preparation of Ionone, for Artificial Violet Oil,
     Artificial Musk, Specification of Patent of Musk Substitute,
     Artificial Neroli, Artificial Lilac, Artificial Hyacinth,
     Artificial Lemon Oil, Artificial Rose Oil, Niobe Oil,
     Bergamiol, Artificial Jasmin Oil, Artificial Cognac
     Oil.--~Appendix.~ Table on Constants of the more Important
     Essential Oils.--~Index.~

          Price 12s. 6d. net (Post Free, 13s. Home;
          13s. 6d. Abroad).

          PUBLISHED BY

          ~SCOTT, GREENWOOD & SON,~

          ~8 BROADWAY, LUDGATE HILL, LONDON E.C.~





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