JACQUES LOEB 743 



demands that the p.d. increase with the increase in the concentration 

 of gelatin ions formed, i.e. with the increase in the concentration of 

 the acid added, and that the p.d. diminish with the increase of the 

 concentration of CI ions. At first, the augmenting influence of the 

 acid (through formation of gelatin chloride) increases more rapidly 

 with increasing concentration of acid than the depressing effect of 

 the CI ions, until a certain part of the gelatin is transformed into 

 ions. From that point on the increase in p.d. due to the ionization 

 of the gelatin increases less rapidly than the depressing effect of the 

 CI ions and the p.d. diminishes again when more acid is added. This 

 has all been discussed more fully and need not be repeated here.^ 



The experiments mentioned in Table I show that LaCls acts in a 

 way entirely similar to HCl. When LaCls solutions of low concen- 

 tration (and of pH 4.7) are added to isoelectric gelatin, the p.d. 

 rises with increasing concentration of LaCls until the concentration 

 is m/6,144, when the p.d, falls again. This suggests that the La ion 

 of the LaCls solution enters into combination with gelatin, as does 

 the H in the case of HCl, by giving rise to gelatin-lanthanum chloride, 

 in which the cation is a complex positively charged gelatin-La ion, 

 while the anion is the CI ion. The increase in ionization of the gela- 

 tin causes an increase in the p.d., while the CI ion depresses the p.d. 

 just as if HCl had been added. There is this difference between the 

 gelatin chloride formed by the reaction between isoelectric gelatin 

 and HCl and the gelatin chloride formed by the reaction between 

 gelatin and LaCls; namely, that the LaCls can be easily washed away 

 while the HCl is held more tenaciously.^ This is easily understood, 

 since the radius of the La ion is so large that in spite of the high charge 

 of the ion it is held with a considerably smaller force by the gelatin 

 than is the H ion, which has no shell of electrons and whose positive 

 nucleus can approach the N of the gelatin very closely. 



The action of solutions of Na4Fe(CN)6 of pH 4.7 on isoelectric 

 gelatin is similar to that of NaOH. The method was the same as 

 that described in the case of LaCls. The results are given in Table II, 

 showing that Na4Fe(CN)6 charges the gelatin negatively, the charge 



'' Loch, J.. Proteins and the theory of colloidal behavior, New York and London, 

 1922, 27; /. Goi. Physiol., 1918-19, i, 237. 



