CONDUCTIVITY OF COLLOIDAL MIXTURES 



311 



effect of those ions upon the colloidal particles. The resistance 

 ofifered by a cylinder of gelatine is so great compared with that 

 offered by a similar volume of 0.52 M NaCl that, when the two 

 are mixed, the part played by the fonner is wholly lost in the 

 enonnous effect produced by the latter. The importance of this 

 fact was not fully realized by the writer until his attention was 



Fig. 5 



called to the results obtained by Fenn.*^ He measured the pre- 

 cipitating effect of 95% alcohol upon gelatine to which had been 

 added various substances. He showed that any electrolyte 

 added to pure gelatine in increasing concentrations decreased the 

 ability of the alcohol to cause precipitation; and that electrolytes 



^ Fenn, W. O. Salt Antagonism in Gelatine. Proc. Natl. Acad. Sci. 2: 534, 

 1916. 



