THE COLLOID-CHEMISTRY OF SOAPS 



17 



Molar equivalents 

 of several different 

 sodium soaps of the 

 acetic acid series were 

 prepared as described 

 above, but in the 

 presence of gradually 

 increasing amounts of 

 water. Water was 

 added until, upon cool- 

 ing the soap mixture 

 to 18 C., a solid gel, 

 or one not showing 

 " syneresis," was no 

 longer obtained. 

 Stated conversely, it 

 was presumed that 

 the limits for water 

 absorption had been 

 exceeded as soon as 

 we obtained only a 

 " solution " of the 

 given soap or one 

 which showed free 

 liquid at the tempera- 

 ture chosen (18 C.). 



The results of an 

 actual experiment are 

 portrayed in Fig. 8. 

 The lowermost mem- 

 bers of the sodium 

 salts of the acetic 

 acid series take up 

 no water at all; they 

 yield only " true " 

 solutions. Sodium 

 caproate forms a true 

 solution in very little 

 water, but when this 

 is slowly evaporated 



