TI1K COLLOID-CHEMISTRY OF SOAP MANUFACTURE 175 



or impossible soap formation by the " cold " process. This 

 conclusion has been drawn from the fact that the fats which do 

 not emulsify readily in the cold also fail to saponify easily. While 

 proper previous emulsification does accelerate saponification, the 

 real difficulty is resident in the nature of the fatty acids present 

 in the more solid fats the higher (solid) fatty glycerids being 

 split with greater difficulty and the resulting fatty acids combin- 

 ini: more slowly with alkali at low temperatures than do the 

 more liquid oils with their lower and more nearly liquid fatty 

 acids. 



For the production of an emulsion, whether soap be made 

 by the cold or the hot process and whether from neutral fat or 

 the free fatty acids, it is necessary to hold distinctly in mind the 

 mere making of the emulsion and its subsequent stabilization. 

 Aid is rendered the first process by the mechanical agitation 

 incident to the mere mixing of the soap-kettle constituents. 

 Usually, also, a new batch of soap is started by running the new 

 mass of fat or oil to be saponified into a kettle containing the 

 soap remnants left from a previous run. But even if a caustic 

 alkali is run at once into a cold or a hot fat, soap formation be.uin> 

 very quickly, for rarely are these substances free from a certain 

 amount of free fatty acid. As previously emphasi/ed. it is not 

 possible to emulsify fat in pure water. In soap manufacture. 

 therefore, the fat -is not emulsified in water but, as is necessary in 

 all such instances^ in a liquid hydrated colloid. Hence the use- 

 fulness of beginning with a soap stock, the greater ease of emulsi- 

 fication if the fat used is liquid at the temperature employed and 

 contain- free fatty acid, and the exceeding simplicity of the whole 

 process if all the soup is made from free fatty acid (by the T\\ IT. 11- 

 ELL process). The first portion of hydrated colloid found 

 or produced in the soap kettle then permits t he fats or fatty acids 

 added subsequently to be properly and permanently dnulsitied 

 in them. 



The ease with which such enmlsilieat ion is obtained is in 

 its turn re-idem in the physical qualities of the fat itself. I 1 

 is obvious that emu l>ifieat ion can be obtained more easily in the 

 case of a low melting point fat. like the liquid oils, than in that 

 of tho more solid fats, like tall" nn or Japan ma Kmul- 



.tie subdivisions of a lii/nnl in a liquid. To get the more 

 solid faN into this state an ineren-e in temperature i- the- 



