JACQUES LOEB 485 



In an analogous way we must assume that isoelectric gelatin can 

 combine loosely with Na4Fe(CN)6 whereby negatively charged com- 

 plex gelatin-Fe(CN)6 ions and positively charged Na ions are formed. 



SUMMARY AND CONCLUSIONS. 



1 . It has been shown in previous publications that when solutions of 

 different concentrations of salts are separated by collodion-gelatin 

 membranes from water, electrical forces participate in addition to 

 osmotic forces in the transport of water from the side of the water to 

 that of the solution. When the hydrogen ion concentration of the 

 salt solution and of the water on the other side of the membrane is 

 the same and if both are on the acid side of the isoelectric point of 

 gelatin {e.g. pH 3.0), the electrical transport of water increases with 

 the valency of the cation and inversely with the valency of the 

 anion of the salt in solution. Moreover, the electrical transport 

 of water increases at first with increasing concentration of the 

 solution until a maximum is reached at a concentration of about 

 11/32, when upon further increase of the concentration of the salt solu- 

 tion the transport diminishes until a concentration of about m/4 is 

 reached, when a second rise begins, which is exclusively or pre- 

 eminently the expression of osmotic forces and therefore needs no 

 further discussion. 



2. It is shown that the increase in the height of the transport curves 

 with increase in the valency of the cation and inversely with the 

 increase in the valency of the anion is due to the influence of the 

 salt on the p.d. (E) across the membrane, the positive charge of the 

 solution increasing in the same way with the valency of the ions 

 mentioned. This effect on the p.d. increases with increasing con- 

 centration of the solution and is partly, if not essentially, the result 

 of diffusion potentials. 



3. The drop in the transport curves is, however, due to the influ- 

 ence of the salts on the p.d. (c) between the liquid inside the pores of 

 the gelatin membrane and the gelatin walls of the pores. According 

 to the Donnan equilibrium the liquid inside the pores must be nega- 

 tively charged at pH 3.0 and this charge is diminished the higher the 

 concentration of the salt. Since the electrical transport is in pro- 

 portion to the product oi E X e and since the augmenting action of 



