THE COLLOID-CHEMISTRY OF SOAP MANUFACTURE 181 



A. SMiTS, 1 F. GOLDSCHMIDT and L. WEissMANN, 2 these views 

 received modification. KRAFFT and WIGLOW observed that when 

 the soaps of the higher fatty acids were studied at low tempera- 

 tures these commonly did not lower the freezing point in the cal- 

 culated amount; and GOLDSCHMIDT found that the electrical con- 

 ductivity was not as high as theory demanded. The same soaps 

 when studied at sufficiently high temperatures did, however, 

 show the behavior of normal electrolytes. Obviously the earlier 

 observers and those working at high temperatures dealt with what 

 were essentially true solutions of soaps in water; the latter stu- 

 dents of the problem, working at lower temperatures and with 

 higher fatty acid soaps, dealt with mixed systems. The former 

 worked in the region A of Figs. 48 and 49 ; the latter anywhere below 

 this but still in regions in which were present solutions of soap-in- 

 water admixed with solutions of water-in-soap. What characteristics 

 of a " true " solution their mixtures stiU showed were dependent 

 upon the presence of the former; the characteristics at variance with 

 those anticipated, in other words, the " colloid " properties of the 

 systems were dependent upon the latter. 



8. The Salting-Out of Mixed Soaps 



The salting out of mixed soaps has been made the object of 

 special study by MERKLEN S and LEiMDoKFER. 4 Both give < 

 lent analyses of the content of soap, water and dissolved sul>- 

 stanees dike alkali and sails) present in the two main phases, the 

 " lye " and the " curd " or " settled " soap, which may be ob- 

 tained after complete or partial salting-out. 



The observations detailed in the previous pages on the saltinu- 

 out of the different soaps help us to explain, we think, in simpler 

 fashion than is generally the case the series of changes observed 

 in the contents of the soap kettle when salted and cooled. In the 

 ordinary salting-nut pi numon sodium chlorid is shoveled 



into the boiling soap kettle in dry form. Assuming that it goes 

 into solution at once, it is nl.vious that there follows a pi-nun 1\ 

 increase in the concentration of the salt in a soap/water syst. -m 



1 A. SUITS: Zeitechr. f. physik. Chcm., 46, 608 (1903). 



' F. GOLDACHMIDT and L. WEISSMANN: Zeitechr. f. Electrochem., 18, 380 

 (1912). 



it', i,, trans, by FRANZ GOLDSCHMIDT. 

 Halle a/S (19<)T 



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



