JACQUES LOEB 93 



from gelatin rendered isoelectric (in the way described in former 

 papers) by adding LiOH, NaOH, etc., to the gelatin. About 18 cc. 

 of 0.01 N NaOH or Ca(0H)2 must be contained in 100 cc. of a 1 per 

 cent solution of isoelectric gelatin to obtain a metal gelatinate with 

 a pH of 7.0; i.e., with neutral reaction. We shall call a solution 

 containing 1 gm. of isoelectric gelatin in 100 cc. a 1 per cent gelatin 

 solution notwithstanding the fact that the gelatin is caused to com- 

 bine with an acid or base. 



We will first show that the gelatin salts with monovalent and bivalent 

 cations influence the rate of diffusion of water in the same sense as is 

 done by common crystalloid salts with monovalent and bivalent 

 cations. Since in the presence of such metal gelatinate water diffuses 

 through a collodion membrane as if its particles were positively 

 charged (as ascertained by experiments with a constant current) we 

 should expect that water should diffuse more rapidly into 1 per cent 

 solution of metal gelatinate with monovalent cations, Li, Na, K, 

 NH4, than with bivalent cations, Mg, Ca, Sr, Ba, etc. This is indeed 

 the case. We proceeded in the same way as in our previous experi- 

 ments. Collodion bags,^ in the shape of Erlenmeyer flasks with 

 about 50 cc. contents, and all with the same surface, were prepared 

 in as uniform a way as possible. The flasks were closed with a 

 perforated rubber stopper through the opening of which a glass tube 

 (with bore of about 2 mm. diameter) serving as a manometer was 

 pushed. These collodion flasks were filled with water distilled in a 

 tin still and having a pH of about 5.2. The collodion bag was put 

 into a beaker filled with a 1 per cent solution of a metal gelatinate 

 and the pressure head of the water in the manometer tube was at 

 the beginning of the experiment about 120 mm. of H2O. The fall 

 of the level of the water in the glass tube was measured in definite 

 intervals. In Figs. 1 and 2 the levels are plotted as ordinates over 

 the time elapsed since the beginning of the experiment. The experi- 



^ The permeability of the collodion bags was tested before each experiment 

 by filling them with m/4 cane sugar and measuring the rate at which water dif- 

 fused into them. When the water rose in the glass tube with a bore of 2 mm. 

 in diameter to a height of about 110 mm. in 20 minutes the membranes were 

 considered serviceable. 



