AMPHOTERIC COLLOIDS. 



V. The Influence of the Valency of Anions upon the Physical 

 Properties of Gelatin. 



By JACQUES LOEB. 



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



(Received for publication, February 21, 1919.) 



It was shown in preceding papers that while all gelatin salts with 

 univalent cation show a comparatively high osmotic pressure, a high 

 degree of swelling, a high viscosity, and a high alcohol number, the 

 gelatin salts with bivalent metal (and trivalent metal) show for the 

 same pH and gelatin concentration a low osmotic pressure, low degree 

 of swelling, low viscosity, and a low alcohol number. Since the con- 

 ductivities of the two types of gelatin salts were found to be practi- 

 cally the same, the valency effect could not be attributed to differ- 

 ences in the degree of ionization and " hydratation" of the gelatin ions. 

 The writer suggested as a tentative explanation the assumption of an 

 aggregate formation of a stoichiometrical character. He had shown 

 that two gelatin ions combine with one bivalent cation and it was 

 suggested that in the process of electrolytic dissociation these two 

 gelatin ions form one anion with two charges. This suggestion is 

 able to explain quantitatively the results actually observed.^ 



In one of his previous pubUcations the writer had already called 

 attention to the fact that bivalent anions differ in their valency effect 

 from bivalent cations.- While SO4 has a similar depressing effect upon 

 the physical properties of gelatin as Ca or Ba, the same does not seem 

 to be true for other bivalent and trivalent anions like oxalate, 

 succinate, tartrate, citrate, or phosphate. The acids of these latter 

 anions seemed to act as if they were monobasic acids, one molecule 

 of these acids being capable of combining with one gelatin ion only. 



1 Loeb, J., /. Gen. Physiol, 1918-19, i, 483. 

 ~ Loeb, J., /. Biol. Chem., 1918, xxxiv, 489. 



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