JACQUES LOEB 751 



hydrogen ion concentration may enter to some extent into these 

 effects but they are probably of only secondary importance. No 

 such effects have thus far been obtained with salts possessing divalent 

 or monovalent ions; i.e., salts of the type Na2S04, CaCl2, and NaCl. 



IV. 



In a gelatin chloride solution of pH 3.0, the greater part of the 

 gelatin is ionized, and since the H ion is held more firmly by the 

 gelatin than the La ion, the addition of LaCls to a solution of gelatin 

 chloride of pH 3.0 should not have any augmenting effect on the 

 p.D. or the osmotic pressure of the gelatin chloride solution. The 

 only effect the addition of LaCls to a solution of gelatin chloride 

 should have is the depressing effect of the CI ions. Hence when we 

 mix a solution of gelatin chloride of pH 3.0 with solutions of LaCls 

 of the same pH the effect on the p.d. and the osmotic pressure should 

 be merely a depression of the values of these latter properties, and 

 the depression should be quantitatively identical with the effect of 

 CaCL or NaCl solutions of the same concentration of CI ions and the 

 same pH. 



This fact had already been ascertained in previous experiments 

 already published,^ but since these direct measurements of p.d. are of 

 such importance for the theory of the origin of the p.d. between colloids 

 and aqueous solutions it seemed advisable to repeat them. 1 gm. of 

 gelatin chloride of pH 3.0 was dissolved in 100 cc. of solutions of 

 various salts all brought to pH 3.0 through the addition of HCl. 

 Collodion bags were filled with these solutions of gelatin chloride in 

 different salts and each bag was dipped into 350 cc. of an aqueous 

 solution of the same concentration of the same salt and the same 

 pK as that inside the collodion bag, but without gelatin. Water 

 diffused into the collodion bag until osmotic equilibrium was estab- 

 Hshed, and the next day the final osmotic pressure and the p.d, 

 between gelatin solution and outside aqueous solution were 

 measured. The solutions of the three salts were prepared in such a 

 way as to have the same concentration of CI. In Fig. 1 are plotted 

 the P.D. as ordinates over the concentration of the CI ions as ab- 

 scissa;. It is obvious that the influence of NaCl, CaClo, and LaCls 



