720 ELECTRIFICATION AND DIFFUSION OF WATER 



shall show that there is no difference between the osmotic effects of 

 the hydroxides and of the chlorides or nitrates, e.g. m/128 NaCl and 

 m/128 NaOH acting qualitatively and quantitatively practically alike 

 in their influence on the rate of diffusion of water through collodion 

 membranes. 



The writer has carried out a series of experiments on the rate of 

 diffusion of water through a collodion membrane separating the pure 

 solvent from a solution. These experiments indicate that this process 

 depends on two kinds of forces; namely, first, those of gas pressure 

 which are clearly recognizable in the case of solutions of non-con- 

 ductors like glucose or saccharose, and second, electrical forces which 

 become predominant in the case of low concentrations of solutions of 

 electrolytes. We shall deal in this paper with the electrical forces. 

 They lead to the result that in the diffusion of water through a col- 

 lodion membrane to a solution of an electrolyte the water molecules 

 are either positively or negatively charged according to the nature 

 of the electrolyte in the solution and that these charges are a factor 

 in the rate of diffusion. The laws or rules controlling this factor can 

 be expressed in the following way. 



1. Solutions of neutral salts possessing a univalent or bivalent 

 cation influence the rate of diffusion of water through a collodion 

 membrane, as if the water particles were charged positively and were 

 attracted by the anion and repelled by the cation of the electrolyte; 

 the attractive and repulsive action increasing with the number of 

 charges of the ion and diminishing inversely with a quantity which 

 we will designate arbitrarily as the "radius" of the ion. The same 

 rule applies to solutions of alkalies. 



2. Solutions of neutral or acid salts possessing a trivalent or tetra- 

 valent cation influence the rate of diffusion of water through a collodion 

 membrane as if the particles of water were charged negatively and 

 were attracted by the cation and repelled by the anion of the elec- 

 trolyte. Solutions of acids obey the same rule, the high electro- 

 static effect of the hydrogen ion being probably due to its small "ionic 

 radius. " 



We shall show first that the assumption of a difference in the sign 

 of the charge of water molecules (according to the two rules just 

 mentioned) explains all the phenomena that can be observed; and 



