AMPHOTERIC COLLOIDS. 



IV. The Influence of the Valency of Cations upon the 

 Physical Propertles of Gelatin. 



by jacques loeb. 



{From the Laboratories of The Rockefeller Institute for Medical Research.) 

 (Received for publication, January 22, 1919.) 



I. introduction. 



In 1901 and 1902 the writer^ published a series of investigations in 

 which he showed that low concentrations of bivalent cations, prac- 

 tically without regard to their chemical nature, e.g. Mg, Ca, Sr, Ba, 

 Zn, Co, Pb, etc., inhibited the toxic action of high concentrations of 

 salts with univalent cations, upon the eggs 'of Fundulus. Trivalent 

 cations like AICI3 and CrCls seemed to act still more effectively than 

 the bivalent ions though it was obvious that secondary influences 

 {e.g. the high hydrogen ion concentration) restricted the limit of 

 their antagonistic influence. This influence of valency the writer 

 attributed to the effect of the electric charges of the ions upon the 

 physical state of the colloidal material. He also found that poly- 

 valent anions, e.g. SO , oxalate, citrate, etc., had under the same con- 

 ditions no antagonistic effect. Since that time cases of an antagonistic 

 action of polyvalent anions have come to light, but this phenomenon 

 is not only less common but also less striking than the antagonistic 

 effect of polyvalent cations. 



It had been shown in the writer's preceding publications on gelatin^ 

 that the salts of gelatin with univalent cations possess a compara- 

 tively high osmotic pressure, a high viscosity, a high degree of swell- 



^ Loeb, J., Arch. ges. Physiol, 1901-02, Ixxxviii, 68; Am. J. Physiol, 1901-02, 

 vi, 411. 



2 Loeb, J., /. Biol Chem., 1918, xxxiii, 531; xxxiv, 77, 395, 489; xxxv, 497; 

 /. Gen. Physiol, 1918-19, i, 39, 237, 363. 



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