216 POTENTIAL DIFFER-E: rES AND ANOMALOUS OSMOSIS 



CI to SO4. Where the wa*'^r is positively charged the reverse order 

 of efficiency exists. " ' 



The fact that the same jncentration of the salts, namely, m/256, 

 was used, has no essential influence on the results. Similar results 

 were obtained when the salt solutions had the osmotic pressure of a 

 m/64 solution of cane sugar. 



Those who have studied phenomena of abnormal osmosis 

 through membranes, Girard,^ Bernstein,^ Bartell and his collabora- 

 tors,^ and Freundlich^ have reached the conclusion that potential 

 differences on the opposite sides of the membrane are responsible 

 for these anomalies in diffusion. The fact that the sign of charge 

 varies in these experiments with the sign of charge of the' pro- 

 tein ion gives a favorable point of attack for the investigation 

 of tlie origin of the potential differences. In order to simpHfy 

 the experiments they were confined to pH from 4.6 to pH 1.9; i.e., 

 to that region where the water diffuses as if it were negatively elec- 

 trified. The method of procedure was as follows, m/256 solutions 

 of one of the four salts mentioned were prepared in different concen- 

 trations of HNO3 and put into collodion bags of about 50 cc. volume, 

 which were lined by a film of gelatin on the inside. These bags were 

 closed with a perforated rubber stopper through which was pushed 

 a glass tube with a diameter of about 2 mm. to indicate the rise of 

 liquid. The collodion bags were put into beakers containing 350 cc. 

 of the same concentration of HNO3 as that inside the bag. Fig. 2 

 gives the rise of the level of liquid in the manometer in one set of 

 experiments after 1 hour at 24°C. The abscissas are the initial pH 

 of the liquid which was the same inside and outside, the ordinates 

 are the rise of the level of liquid after 1 hour. It is obvious in this 

 case that the curves have a minimum near the isoelectric point of 

 gelatin, that the rate of diffusion of water into the solution rises 



^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. 



■* Bernstein, J., Elektrobiologie, Braunschweig, 1912. 



^Bartell, F. E., /. Am. Chem. Soc, 1914, xxxvi, 646. Bartell, F. E., and 

 Hocker, C. D., /. Am. Chem. Soc, 1916, xxxviii, 1029, 1036. Bartell, F. E., 

 and Madison, O. E., J. Physical Chem., 1920, xxiv, 593. 



^Freundlich, H., Kollotd. Z., 1916, xviii, 11. 



