286 COLLOIDS AND ELECTROLYTES 



These experiments can be repeated with any other neutral or 

 alkaline salt with univalent cation. Figs. 8 and 9 show the depressing 

 effect of the addition of neutral salts (Fig. 8) or of alkahes (Fig. 9) 

 to a solution of m/256 Na4Fe(CN)6. Again the influence of the 

 valency of the cation and the identity of the effects of alkahes and 

 neutral salts with the same cation are manifest. 



In all these experiments in which the particles of water were posi- 

 tively charged the depressing effect of the addition of salt was greater 

 when the cation of the salt was bivalent than when it was 

 monovalent. 



Such experiments have been made with a large number of salts, all 

 yielding the same result; namely, that the depressing effect of the 

 addition of increasing concentrations of alkahes and neutral salts 

 upon the attraction of water by gelatin solutions is paralleled by the 

 influence of the addition of increasing concentrations of salts upon 

 the attraction of water by solutions of salts, in the presence of which 

 water is positively charged. This raises the question whether or not 

 the depressing influence of high concentrations of electrolytes upon 

 the osmotic pressure of gelatin is necessarily connected with the 

 colloidal character of gelatin or whether it is based upon a much more 

 general property of matter; namely, the influence of electrolytes 

 upon the electrification and the rate of diffusion of water through 

 membranes. We only wish to point out this possibihty without 

 deciding definitely. 



It may suffice to point out that the influence of the concentration 

 and the valency of electrolytes on the osmotic pressure of gelatin 

 solutions can be demonstrated equally well for the phenomenon of 

 swelhng and the curves representing this influence are similar to those 

 given in this paper for the influence on the osmotic pressure. 



///. Negatively Charged Particles of Water. 



When we separate solutions of gelatin-acid salts from pure water 

 by a collodion membrane, the particles of water diffusing through 

 the membrane act as if they were negatively charged. That this is 

 so can be demonstrated by experiments on electrical endosmose. 



