JACQUES LOEB 293 



of the collodion membrane with a protein is necessary since other- 

 wise water will diffuse through the collodion membrane in the form 

 of positively charged particles and then the case is no longer com- 

 parable with that of gelatin-acid salts. This gelatin treatment of 

 the collodion membrane is not required when we wish to experiment 

 with positively charged particles of water, since water assumes prac- 

 tically always a positive charge when in contact with a collodion mem- 

 brane free from gelatin, even in comparatively high concentrations 

 of acid. 



If we use membranes which had contained a 1 per cent gelatin 

 solution over night but were then freed from the gelatin by a number 

 of washings with warm water, and if we substitute for the gelatin- 

 acid salt a crystalloidal salt which causes water to be charged nega- 

 tively in such gelatin-treated membranes, e.g. m/512 AI2CI6, we 

 notice the same depressing effect of an increase of the concentration 

 of electrolytes on the initial rate of diffusion of water into the 

 solution as was described in the case of the solutions of gelatin-acid 

 salts. When we separate a collodion bag filled with m/512 AI2CI6 

 (which causes water to be charged negatively) and put it into H2O, 

 the level of liquid in the manometer will rise to a height of about 

 300 mm. in 20 minutes. When we add varying quantities of a 

 neutral salt to the m/512 solution of AI2CI6, and put the same con- 

 centration of salt into the outside beaker containing the water — in 

 order to eliminate the direct effect of the salt added upon the rate 

 of diffusion — we notice that the rate of diffusion of water will diminish 

 the more rapidly the more salt we add. This is illustrated in Fig. 15. 

 NaNOs and CaCl2 have about the same depressing effect, showing 

 that the depression is not due to the influence of the cation; while 

 SO4 and still more citrate depress much more powerfully than the 

 chlorides, showing that the depression is due to the influence of the 

 increasing concentration of the anion upon the negatively charged 

 particles of water. 



Similar experiments were made with solutions of CaCl2 which were 

 rendered sufficiently acid in order to cause the water to be charged 

 negatively. If we select m/128 solutions of such acidulated CaCl2 as 

 a substitute for gelatin-acid solutions, we find that the addition of 

 acid as well as of neutral salt causes a depression of the influence of 



