576 CAUSE OF INFLUENCE OF IONS. II 



The writer has duplicated the majority of the experiments he has 

 thus far pubHshed on free osmosis by experiments on electrical 

 endosmose and there is a fair degree of similarity in the two cases. 



SUMMARY. 



1. It had been shown in previous publications that when pure 

 water is separated from a solution of an electrolyte by a collodion 

 membrane the ion with the same sign of charge as the membrane 

 increases and the ion with the opposite sign of charge as the membrane 

 diminishes the rate of diffusion of water into the solution; but that 

 the relative influence of the oppositely charged ions upon the rate of 

 diffusion of water through the membrane is not the same for different 

 concentrations. Beginning with the lowest concentrations of elec- 

 trolytes the attractive influence of that ion which has the same sign of 

 charge as the collodion membrane upon the oppositely charged water 

 increases more rapidly with increasing concentration of the electrolyte 

 than the repelling effect of the ion possessing the opposite sign of 

 charge as the membrane. When the concentration exceeds a certain 

 critical value the repelling influence of the latter ion upon the water 

 increases more rapidly with a further increase in the concentration 

 of the electrolyte than the attractive influence of the ion having the 

 same sign of charge as the membrane. 



2. It is shown in this paper that the influence of the concentration 

 of electrolytes on the rate of transport of water through collodion 

 membranes in electrical endosmose is similar to that in the case of 

 free osmosis. 



3. On the basis of the Helmholtz theory of electrical double layers 

 this seems to indicate that the influence of an electrolyte on the rate 

 of diffusion of water through a collodion membrane in the case of 

 free osmosis is due to the fact that the ion possessing the same sign 

 of charge as the membrane increases the density of charge of the latter 

 while the ion with the opposite sign diminishes the density of charge 

 of the membrane. The relative influence of the oppositely charged 

 ions on the density of charge of the membrane is not the same in all 

 concentrations. The influence of the ion with the same sign of charge 

 increases in the lowest concentrations more rapidly with increasing 

 concentration than the influence of the ion with the opposite sign of 

 charge, while for somewhat higher concentrations the reverse is true. 



