THE COLLOID-CHEMISTRY OF SOAPS 113 



concentration of the cation is reached a critical zone commences in which 

 jelly formation or precipitation appears to depend entirely upon the rela- 

 tive proportions of adsorbed cations and anions. If at the commence- 

 ment of this critical /one the residual negative charge ... is sufficient 

 to maintain a perfect dispersion . . . jelly formation will ensue at higher 

 concentrations. If this residual negative charge ... is insuflieient . . . 

 if agglutination, aggregation and sedimentation under the influence of 

 gravity has already commenced, precipitation necessarily ensues at 

 higher concentrations. ... If at the critical point the sum total <>t 

 adsorbed anions is not sufficiently in excels of that of adsorbed cations to 

 injure perfect dispersion, precipitation instead of jelly formation ensues. 

 Thi> explains the necessity for a certain minimum concentration of NaOH 

 with its readily adsorbed OH ions to insure jelly formation in the case 

 cited above." 



The contradictory nature of the explanations here reviewed 

 is self-evident. To secure the proper results CLOWES holds that 

 the soap must be " alkaline to phenolphthalein." Our own soap, 

 which in practice worked quite like his, was prepared by adding 

 to each other the chemically equivalent weights of fatty acid 

 and alkali necessary to yield a " neutral " soap. In the coin -ni- 

 trations in which we employed our stock soap it was not alkaline 

 to phenolphthalein. The same kind of soap stock or one more 

 decidedly "acid" was employed by all the other students in 

 this field. In fact, it would seem that, with the exception of 

 CLOWES, the majority of observers had inclined to the belief that an 

 overplus of acid in their soap systems was necesssary for an under- 

 standing of the viscosity changes. Nevertheless, and independ- 

 cntlv of all hypothesis, there is reported throughout the experi- 

 ment* of all these workers (including our own) the same sequence 

 of observed facts which has been set down in detail in the pre- 

 ceding pages, namely, nn initial increase in viscosity resulting 

 ultimately (when the soap system is not too dilute) in Delation, 

 followed by a decrease in viscosity and a gradually inercasinR 

 dehydration and complete separation of the soap. 



c. On the Theory of the " Ralting-out nps. We refrain 



from a detailed criticism of the views of these authors. It is 

 self-apparent how all ided notion^ of jelly formation in 



(like the elect rieal . mu-t r< tine to ^rief as SOOH as it i- IVIIH in 

 that SUch jell i< may ] produced from non-iKjUeous solvents 

 and anhydrous soaps and under cilCUinstances which allow of 

 I" t lie orthodox conditions deemed necessary for the develop- 



