718 ELECTRIFICATION AND DIFFUSION OF WATER 



SO called negative osmosis in which the solvent moves from a solution 

 of higher to one of lower molecular concentration and which have been 

 described and studied by Dutrochet, Thomas Graham, Girard, Flusin, 

 Bartell, Bernstein, Freundlich,^ and others. 



Girard, Bernstein, and Bartell have reached the conclusion that 

 potential differences caused by the electrolyte play a part in these 

 phenomena of abnormal osmosis, and our results are in agreement 

 with this view. We cannot agree, however, with the view of Girard 

 and of Freundlich that the H and OH ions play the decisive part in 

 the electrical phenomena which lead to abnormal osmosis. This 

 view of a privileged position of the H and OH ions in these phenom- 

 ena rests on the famous experiments of Perrin^ on electric endosmose. 

 It had been known that when a galvanic current is sent through a 

 porous diaphragm bounded on both sides by water the latter migrates 

 to one of the two electrodes. No reason could be assigned for the 

 direction of the migration, until Perrin made the remarkable discovery 

 that when a current is sent through a colloidal diaphragm (gelatin, 

 silk, etc.) the direction of motion of the water can be altered at will; 

 addition of acid causes the water to move to the anode, addition of 

 alkali to the cathode. This phenomenon was explained by Perrin on 

 the assumption that the H or OH ions of the water are adsorbed by 

 the surface of the diaphragm transferring their charges to the latter. 

 A double layer is formed, the molecules of water adjacent to the dia- 

 phragm assuming the opposite electrical charge. However, Perrin 

 noticed and pointed out a serious difficulty in this assumption, namely 

 that no other monovalent ions except the H and OH ions are capable 

 of such an apparent transfer of their charges to the diaphragm. 



The writer is under the impression that we must discriminate be- 

 tween two kinds of diaphragms, namely those which consist of material 



^ Bernstein, J., Elektrobiologie, 1912. Bartell, F. E., /. Am. Chem. Soc, 

 1914, xxxvi, 646. Bartell, F. E., and Hocker, C. D., /. Am. Chem. Soc, 1916, 

 xxxviii, 1029, 1036. Freundlich, H., Kolloid-Z., 1916, xviii, 11. Girard, P., Compt. 

 rend. Acad., 1908, cxlvi, 927; 1909, cxlviii, 1047, 1186; 1910, cl, 1446; 1911, cliii, 

 401; La pression osmotique et le mechanisme de I'osmose, Publications de la 

 Societe de Chimie-physique, Paris, 1912. Flusin, G., Ann. chim. et phys., 1908, 

 xiii, 480. 



^ Perrin, J., Notice sur les titres et travaux scientifiques de M. Jean Perrin, 

 Paris, 1918. 



