174 SOAPS AND PROTEINS 



Having observed how the type of oil or fat employed determines 

 from a chemical point of view whether a cold or hot process of 

 manufacture will yield best results, we need to review the whole 

 process once more from the point of view of the changes which 

 are incident to the mere mixing of any fat or oil with an alkali. 

 The empiric instructions covering the process are again many. 1 

 In the case of certain " oils " a stronger alkali may be used than 

 when the more solid " fats " are employed; or in the case of the 

 former ah 1 the alkali may be added more quickly or in one charge 

 while in the latter several successive and smaller charges must 

 be used. The soap maker has here again learned from practical 

 experience what may be done with any individual oil or fat, or 

 what may be accomplished by mixing or blending such. What 

 do these things mean? 



The older soap chemists recognized that, in their " cold " 

 process of manufacture, emulsification of the fat played an 

 important role; what happened in the hot process' was not so 

 clear. 



5. The Mixing of Fat with Alkali. Initial Emulsification 



J. LEIMDORFER 2 has correctly said that the colloid-chemistry 

 of soaps begins with the commencement of their manufacture 

 and in defense of this remark has emphasized anew the signifi- 

 cance of emulsification in the cold method of soap manufacture. 

 LEIMDORFER points out that when any fat is mixed with caustic 

 soda solution the two are emulsified in each other and that in 

 the " gum " or jelly which results, the process of saponification 

 then proceeds to an end. According to LEIMDORFER the soap 

 formed " adsorbs " the alkali and the fat, the further reaction 

 between these materials occurring in the soap gel itself, as it were. 

 We shall have occasion to touch upon the " adsorption " phases 

 of this explanation later. At this point we wish merely to con- 

 sider in somewhat greater detail the initial process of emulsi- 

 fication. 



It is held by various authors that the occurrence or non- 

 occurrence of this initial process of emulsification makes possible 



1 As an illustration of the technical literature extant see, for example, 

 ALEXANDER WATT: The Art of Soap Making, Ninth Imp., London (1918). 



2 J. LEIMDORFER: Technologic der Seife, 5, Dresden (1911). 



