JACQUES LOEB 103 



in the height of the level of water in the manometer with time until 

 the equilibrium is reached. 1 per cent solutions of gelatin chloride, 

 nitrate, oxalate, tartrate, citrate, and sulfate were prepared by making 

 up the solution with the addition of as much of these acids to 1 gm. 

 isoelectric gelatin as was required to produce a pH of 3.5. These 1 per 

 cent gelatin solutions were put into collodion flasks containing the 

 glass tube as described and each flask was put into a beaker with 

 350 cc. of distilled water the pH of which was made 3.0 by adding 

 in each case the same acid as that of the gelatin. In Fig. 6 is plotted 

 the rise and the final osmotic pressure of these solutions. The 

 osmotic pressure reached in the case of gelatin sulfate was about 159 

 mm. while for the other salts it was almost twice as high (between 

 260 and 310 mm.). It is also noticeable from the curves that the 

 relative velocity of rise during the 1st hour of the experiment also 

 showed about the same ratio of almost 1: 2 as the final equilibrium. 

 The results thus confirm our expectation that on account of the 

 electrification of the water molecules both the rate of diffusion as 

 well as the final osmotic equilibrium are affected in the same sense. 

 If we wish to explain the differences between the observed osmotic 

 pressure of solutions of calcium and sodium gelatinate or of gelatin 

 chloride and gelatin sulfate, exclusively on the basis of van't Hoff's 

 law, we are compelled to seek refuge in the assumption of the forma- 

 tion of aggregates of gelatin ions by which the number of these particles 

 is diminished without diminution of the number of their charges.^^ 

 This suggestion was first offered by Bayliss^- when he found that the 

 osmotic pressure of the colloid Congo red was considerably lower 

 than was to be expected according to the molecular concentration 

 and the conductivity of the solution. This assumption, however, 

 which the writer had also tentatively accepted to explain the differ- 

 ence between the osmotic pressure of calcium and sodium gelatinate 

 of the same concentration rests only on the facts which the assumption 

 is supposed to explain, while the connection between rate of diffusion 

 of water and osmotic pressure of a solution holds generally in all 



^^ The writer has shown that the conductivity of 1 per cent Na gelatinate and 

 of 1 per cent Ca gelatinate at the same pH is identical. 

 i^Bayliss, W. M., Proc. Roy. Soc. London, Series B, 1911-12, Ixxxiv. 229. 



