186 SOAPS AND 1'1;<>TKINS 



concentrated one. Without pointing out that none of the authors 



who have used the concepts of adsorption for the elucidation of 

 various problems in soap-making have ever supported their con- 

 tentions with any figures, it is obvious, if the views expressed 

 above are correct, that irhal they have taken as evidences of " ad- 

 xorittion " between various so-called " dissolved " substances and the 

 soaps (alkali, fat and soap in the original soap kettle; water, salt 

 and soap in the salting-out process; sodium carbonate, water- 

 glass and soap in the " filling " process, etc.) can all be more easily 

 understood merely as the expression of the emulsification of one type 

 of liquid (like fat or salt solution) in a second (the soaps of the 

 various fatty acids with their variable hydration capacities). 



3 



In the finishing of soaps (particularly the toilet soaps) for the 

 market, there is often added glycerin or some other alcohol. 

 Under such circumstances the product is more likely to be trans- 

 parent. The reasons for this are found in the nature of the col- 

 loid-chemical system soap/alcohol as compared with that of soap/ 

 water. The former is uniformly clearer than the latter. From 

 certain soap/alcohol systems, like sodium palmitate with benzyl 

 alcohol, finished soaps may be obtained which are glasslike in 

 appearance. 



10. Some Physical Constants of Market Soaps 



Exclusive of admixture with non-saponifiable materials, exclu- 

 sive of the effects of all additions in the way of excess alkali, salts 

 or fillers and exclusive also of variation in type of solvent (pres- 

 ence or absence of glycerin or other alcohols) a correct estimate of 

 what will be the physico-chemical properties of any soap must 

 evidently depend first, upon the kind, the number and the relative 

 proportions of the fatty acids found in the original fat used for 

 saponification. With a given base and with a constant solvent 

 (water) the result is that obtained when such a mixture of dif- 

 ferent soaps is allowed to come together in the presence of a lim- 

 ited amount of water. 



The ordinary bar of pure soap is therefore essentially only a 

 solid " solution " of water in a mixture of sodium soaps. Except 



