JACQUES LOEB 271 



3. When we separate solutions of acid from pure water by a mem- 

 brane previously treated with gelatin, negative osmosis occurs; i.e., 

 practically no water can diffuse into the solution, while the molecules 

 of solution and some water diffuse out. When we separate solutions 

 of acid from pure water by collodion membranes not treated with 

 gelatin, positive osmosis will occur; i.e., water will diffuse rapidly 

 into the solution and the more rapidly the higher the valency of the 

 anion. 



4. These differences occur only in that range of concentrations of 

 electrolytes inside of which the forces determining the rate of diffusion 

 of water through the membrane are predominantly electrical; i.e., in 

 concentrations from to about m/16. For higher concentrations of 

 the same electrolytes, where the forces determining the rate of diffusion 

 are molecular, the osmotic behavior of the two types of membranes 

 is essentially the same. 



5. The differences in the osmotic behavior of the two types of 

 membranes are not due to differences in the permeability of the 

 membranes for solutes since it is shown that acids diffuse with the 

 same rate through both kinds of membranes. 



6. It is shown that the differences in the osmotic behavior of the 

 two t3rpes of collodion membranes towards solutions of acids and of 

 salts with trivalent cation are due to the fact that in the presence of 

 these electrolytes water diffuses in the form of negatively charged 

 particles through the membranes previously treated with gelatin, 

 and in the form of positively charged particles through collodion 

 membranes not treated with gelatin. 



7. A treatment of the collodion membranes with casein, egg 

 albumin, blood albumin, or edestin affects the behavior of the 

 membrane towards salts with trivalent or tetravalent cations and 

 towards acids in the same way as does a treatment with gelatin; 

 while a treatment of the membranes with peptone prepared from 

 egg albumin, with alanine, or with starch has no such effect. 



