The book of Soap Manufacture, by W. H. Simmons pptx

developed very slowly, being essentiallycarried on by rule-of-thumb methods, butthe classic researches of Chevreul on theconstitution of fats at once placed theindustry upon a scientific

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THE HANDBOOK OF SOAP MANUFACTURE ***

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THE HANDBOOK OF

SOAP MANUFACTURE

BY

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

AND

H A APPLETON

WITH TWENTY-SEVEN

ILLUSTRATIONS

LONDONSCOTT, GREENWOOD & SON

"THE OIL AND COLOUR TRADES

Footnotes have been moved to the end ofthe chapter and minor typos have beencorrected.

In the general advance of technicalknowledge and research during the lastdecade, the Soap Industry has notremained stationary While there has notperhaps been anything of a veryrevolutionary character, steady progresshas still been made in practically allbranches, and the aim of the present work

is to describe the manufacture ofHousehold and Toilet Soaps as carriedout 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 inthis we feel justified, as in these days ofstrenuous competition, no soap-maker canhope to compete successfully with hisrivals unless he has a sound theoretical aswell as practical knowledge of the nature

of the raw materials he uses, and thereactions taking place in the pan, or atother stages of the manufacture We alsoventure to hope that the work may proveuseful to Works' Chemists and otherAnalysts consulted in connection with thisIndustry

At the same time, in the greater part of thebook no chemical knowledge is necessary,the subject being treated in such a way that

it is hoped those who are not directlyengaged in the manufacture of soap, but

who desire a general idea of the subject,will find it of value.

In the sections dealing with thecomposition and analysis of materials,temperatures are expressed in degreesCentigrade, these being now almostinvariably used in scientific work In therest of the book, however, they are given

in degrees Fahrenheit (the degreesCentigrade being also added in brackets),

as in the majority of factories these arestill used

As regards strengths of solution, in somefactories the use of Baumé degrees ispreferred, whilst in others Twaddelldegrees are the custom, and we havetherefore given the two figures in allcases

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 toexpress our results in this way, assuggested by Allen in Commercial

Organic Analysis, and all our records,

from which most of the figures for thechief oils and fats are taken, are so stated.For the illustrations, the authors areindebted to Messrs E Forshaw & Son,Ltd., H D Morgan, and W J Fraser &Co., Ltd

W H S

H A A

London, September, 1908.

Researches of Chevreul and Berthelot—Mixed Glycerides—Modern Theories ofSaponification—Hydrolysis accelerated

by (1) Heat or Electricity, (2) Ferments,Castor-seed Ferment, Steapsin, Emulsin,and (3) Chemical Reagents, SulphuricAcid, Twitchell's Reagent, HydrochloricAcid, Lime, Magnesia, Zinc Oxide, Sodaand Potash

CHAPTER III

Raw Materials used in Soap-making

Fats and Oils—Waste Fats—Fatty Acids

—Less-known Oils and Fats of LimitedUse—Various New Fats and OilsSuggested for Soap-making—Rosin—

Alkali (Caustic and Carbonated)—Water

—Salt—Soap-stock

CHAPTER IV

Bleaching and Treatment of RawMaterials intended for Soap-making

Palm Oil—Cotton-seed Oil—Cotton-seed

"Foots"—Vegetable Oils—Animal Fats—Bone Fat—Rosin

Cold Process Soaps—Saponificationunder Increased or Diminished Pressure—

Soaps, Smooth and Marbled—Pasting orSaponification—Graining Out—Boiling

on Strength—Fitting—Curd Soaps—CurdMottled—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—ElectricalProduction of Soap

CHAPTER VI

Treatment of Settled Soap

Cleansing—Crutching—Liquoring of

Soaps—Filling—Neutralising, Colouringand Perfuming—Disinfectant Soaps—Framing—Slabbing—Barring—Open and

Cooling

CHAPTER VII

Toilet, Textile and Miscellaneous Soaps

Toilet Soaps—Cold Process soaps—Settled Boiled Soaps—Remelted Soaps—Milled Soaps—Drying—Milling andIncorporating Colour, Perfume, orMedicament—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 SilkIndustries—Patent Textile Soaps—Miscellaneous Soaps.

CHAPTER VIII

Soap Perfumes

Essential Oils—Source and Preparation—Properties—Artificial and SyntheticPerfumes

CHAPTER IX

Glycerine Manufacture and Purification

Treatment of Lyes—Evaporation to CrudeGlycerine—Distillation—Distilled andDynamite Glycerine—Chemically Pure

Decolorisation—Glycerine obtained byother methods of Saponification—Yield

of Glycerine from Fats and Oils

Table of the Specific Gravities ofSolutions of Caustic Soda

APPENDIX D

Table of Strength of Caustic PotashSolutions at 60° F

Index

CHAPTER I.

INTRODUCTION.

Definition of Soap—Properties— Hydrolysis—Detergent Action.

It has been said that the use of soap is agauge of the civilisation of a nation, butthough this may perhaps be in a greatmeasure correct at the present day, the use

of soap has not always been co-existentwith civilisation, for according to Pliny

(Nat Hist., xxviii., 12, 51) soap was first

introduced into Rome from Germany,having been discovered by the Gauls, whoused the product obtained by mixing goats'

tallow and beech ash for giving a brighthue to the hair In West Central Africa,moreover, the natives, especially the Fantirace, have been accustomed to washthemselves with soap prepared by mixingcrude palm oil and water with the ashes ofbanana and plantain skins Themanufacture of soap seems to haveflourished during the eighth century inItaly and Spain, and was introduced intoFrance some five hundred years later,when factories were established atMarseilles for the manufacture of olive-oil soap Soap does not appear to havebeen made in England until the fourteenthcentury, and the first record of soapmanufacture in London is in 1524 Fromthis time till the beginning of thenineteenth century the manufacture of soap

developed very slowly, being essentiallycarried on by rule-of-thumb methods, butthe classic researches of Chevreul on theconstitution of fats at once placed theindustry upon a scientific basis, andstimulated by Leblanc's discovery of aprocess for the commercial manufacture ofcaustic soda from common salt, theproduction of soap has advanced by leapsand bounds until it is now one of the mostimportant 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 strictlychemical sense it refers to combinations

of fatty acids with metallic bases, a

definition which includes not only sodiumstearate, oleate and palmitate, which formthe bulk of the soaps of commerce, butalso the linoleates of lead, manganese,etc., used as driers, and variouspharmaceutical preparations, e.g., mercury oleate (Hydrargyri oleatum),

zinc oleate and lead plaster, together with

a number of other metallic salts of fattyacids Technically speaking, however, themeaning of the term soap is considerablyrestricted, being generally limited to thecombinations of fatty acids and alkalies,obtained by treating various animal orvegetable fatty matters, or the fatty acidsderived therefrom, with soda or potash,the former giving hard soaps, the lattersoft soaps

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

soap-H Jackson has, however, recentlypatented (Eng Pat 6,712, 1906) the use ofammonium oleate for laundry work Thisdetergent is prepared in the wash-tub atthe time of use, and it is claimed thatgoods are cleansed by merely immersingthem in this solution for a short time andrinsing in fresh water

Neither of the definitions given aboveincludes the sodium and potassium salts ofrosin, commonly called rosin soap, for theacid constituents of rosin have been

shown to be aromatic, but in view of theanalogous properties of these resinates totrue soap, they are generally regarded aslegitimate constituents of soap, havingbeen used in Great Britain since 1827, andreceiving legislative sanction in Holland

in 1875

Other definitions of soap have been given,based not upon its composition, but uponits properties, among which may bementioned that of Kingzett, who says that

"Soap, considered commercially, is abody which on treatment with waterliberates alkali," and that of Nuttall, whodefines soap as "an alkaline or unctuoussubstance 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 theydissolve more slowly, and owing to slight

decomposition, due to hydrolysis (vide

infra), the solution becomes distinctly

turbid Sodium oleate is peculiar in notundergoing hydrolysis except in verydilute solution and at a low temperature

On cooling a hot soap solution, a jelly ofmore or less firm consistence results, aproperty possessed by colloidal bodies,such as starch and gelatine, incontradistinction to substances whichunder the same conditions depositcrystals, due to diminished solubility ofthe salt at a lower temperature

Krafft (Journ Soc Chem Ind., 1896,

206, 601; 1899, 691; and 1902, 1301) andhis collaborators, Wiglow, Strutz and

Funcke, have investigated this property ofsoap solutions very fully, the researchesextending over several years In the light

of their more recent work, the molecules,

or definite aggregates of molecules, ofsolutions which become gelatinous oncooling move much more slowly than themolecules in the formation of a crystal, butthere is a definite structure, althougharranged differently to that of a crystal Inthe case of soda soaps the colloidalcharacter increases with the molecularweight of the fatty acids

Soda soaps are insoluble in concentratedcaustic lyes, and, for the most part, instrong solutions of sodium chloride, hencethe addition of caustic soda or brine to asolution of soda soap causes the soap to

separate out and rise to the surface.Addition of brine to a solution of potashsoap, on the other hand, merely results indouble decomposition, soda soap andpotassium chloride being formed, thus:—

C17H35COOK + NaCl = C17H35COONapotassium

stearate

sodiumchloride

sodiumstearate

The solubility of the different soaps in saltsolution varies very considerably Whilstsodium stearate is insoluble in a 5 percent solution of sodium chloride, sodiumlaurate requires a 17 per cent solution toprecipitate it, and sodium caproate is notthrown out of solution even by a saturatedsolution

Hydrolysis of Soap.—The term

"hydrolysis" is applied to any resolution

of a body into its constituents where thedecomposition is brought about by theaction of water, hence when soap is

treated with cold water, it is said to

undergo hydrolysis, the reaction takingplace being represented in its simplestform by the equation:—

2NaC18H35O2+ H2O = NaOH + HNa(C18sodium

causticsoda

acid sodiumstearate

The actual reaction which occurs has beenthe subject of investigation by manychemists, and very diverse conclusionshave been arrived at Chevreul, thepioneer in the modern chemistry of oils

and fats, found that a small amount ofalkali was liberated, as appears in theabove equation, together with theformation of an acid salt, a very minutequantity of free fatty acid remaining in

solution Rotondi (Journ Soc Chem.

Ind., 1885, 601), on the other hand,

considered that a neutral soap, on beingdissolved in water, was resolved into abasic and an acid salt, the former readilysoluble in both hot and cold water, thelatter insoluble in cold water, and onlyslightly soluble in hot water He appears,however, to have been misled by the factthat sodium oleate is readily soluble incold water, and his views have beenshown to be incorrect by Krafft and Stern

(Ber d Chem Ges , 1894, 1747 and

1755), who from experiments with pure

sodium palmitate and stearate entirelyconfirm the conclusions arrived at byChevreul.

The extent of dissociation occurring when

a soap is dissolved in water depends uponthe nature of the fatty acids from which thesoap is made, and also on theconcentration of the solution The sodiumsalts of cocoa-nut fatty acids (capric,caproic and caprylic acids) are by far themost easily hydrolysed, those of oleicacid and the fatty acids from cotton-seedoil being dissociated more readily thanthose of stearic acid and tallow fattyacids The decomposition increases withthe amount of water employed

The hydrolytic action of water on soap isaffected very considerably by the

presence of certain substances dissolved

in the water, particularly salts of calciumand magnesium Caustic soda exerts amarked retarding effect on the hydrolysis,

as do also ethyl and amyl alcohols andglycerol

Detergent Action of Soap.—The property

possessed by soap of removing dirt is onewhich it is difficult to satisfactorilyexplain Many theories, more or lesscomplicated, have been suggested, buteven now the question cannot be regarded

as solved

The explanation commonly accepted isthat the alkali liberated by hydrolysisattacks 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 thisview, and considered that the value of asoap 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 hepoints out, the liberated alkali would befar more likely to recombine with the acid

or acid salt from which it has beenseparated, than to saponify a neutralglyceride, while, further, unsaponifiablegreasy matter is removed by soap aseasily as saponifiable fat, and there can be

no question of any chemical action of thefree alkali in its case Yet anotherargument against the theory is thathydrolysis is greater in cold and dilute

solutions, whereas hot concentrated soapsolutions are generally regarded as havingthe best detergent action.

Rotondi (Journ Soc Chem Ind., 1885,

601) was of the opinion that the basicsoap, which he believed to be formed byhydrolysis, was alone responsible for thedetergent action of soap, this basic soapdissolving fatty matter by saponification,but, as already pointed out, his theory ofthe formation of a basic soap is nowknown to be incorrect, and his conclusionsare therefore invalid

Several explanations have been suggested,based on the purely physical properties ofsoap solutions Most of these areprobably, at any rate in part, correct, andthere can be little doubt that the ultimate

solution of the problem lies in thisdirection, and that the detergent action ofsoap will be found to depend on many ofthese properties, together with otherfactors not yet known.

Jevons in 1878 in some researches on the

"Brownian movement" or "pedesis" ofsmall particles, a movement of theparticles which is observed to take placewhen clay, iron oxide, or other finelydivided insoluble matter is suspended inwater, found that the pedetic action wasconsiderably increased by soap andsodium silicate, and suggested that to thisaction of soap might be attributed much ofits cleansing power

Alder Wright considered that the alkaliliberated by hydrolysis in some way

promoted contact of the water with thesubstance to be cleansed, and Knappregarded the property of soap solutionsthemselves to facilitate contact of thewater with the dirt, as one of the chiefcauses of the efficacy of soap as adetergent.

Another way in which it has beensuggested that soap acts as a cleanser isthat the soap itself or the alkali set free byhydrolysis serves as a lubricant, makingthe dirt less adherent, and thus promotingits removal

The most likely theory yet advanced is thatbased on the emulsifying power of soapsolutions The fact that these will readilyform emulsions with oils has long beenknown, and the detergent action of soap

has frequently been attributed to it, theexplanation given being that the alkali setfree by the water emulsifies the fattymatter 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 acotton-seed oil containing free acidity, noemulsion is produced with an oil fromwhich all the acidity has been removed, orwith kerosene, whereas a N/10 solution ofsodium oleate will readily give anemulsion with either, thus proving that theemulsification 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 onthe emulsification and foaming of liquidsand on the formation of bubbles Theformer considers that there are twoproperties of a liquid which play animportant part in the phenomenon, (1) itmust have considerable viscosity, and (2)its surface tension must be low Quinckeholds similar views, but considers that nopure liquid will foam.

Soap solution admirably fulfils Plateau'ssecond condition, its surface tension beingonly about 40 per cent of that of water,while its cohesion is also very small; and

it is doubtless to this property that itsemulsifying power is chiefly due So far

as viscosity is concerned, this can havebut little influence, for a 1 per cent