LOWEST
BEST
JOSLIN SCHMIDT & CO.,
Essential Oils
Artificial Perfumes.
ERNEST J. PARRY, B.Sc. (Lond.) , F.I.C., F.C.S.
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.
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