JACQUES LOEB 



579 



The fact that the dibasic and tribasic anions which have no or 

 only a shght antagonistic effect act Hke monobasic acids towards 

 gelatin harmonizes with the hypothesis of aggregation. Our idea of 

 aggregation is a stoichiometrical one, making the number of gelatin 

 ions forming one aggregate of gelatin ions a simple multiple of the 

 valency number of the polyvalent ion with which they are in combi- 

 nation. Since phosphoric, citric, tartaric, succinic, and practically 

 also oxalic acids behave like monobasic acids, i.e. since they can bind 

 only one gelatin molecule, they cannot be expected to cause any aggre- 

 gate formation and hence cannot produce any antagonistic salt 

 action. 



275 



250 



225 



200 



175 



150 



125 



100 



ccQGI N HCl 15 13.5 12.0 10.5 9 7.5 6 4.5 3 1.5 



CCCOIn oxalic acid 2.5 5.0 7.5 10 123 15 175 20 22.5 25 



pH 3.5 345 3.5 3.5 3.5 3.5 3.5 3.45 3.5 3.5 35 



Fig. 12. Showing that oxalic acid has practically no antagonistic effect on the 

 influence of HCl upon the osmotic pressure of gelatin. 



SUMMARY. 



1. When we plot the values of osmotic pressure, swelling, and vis- 

 cosity of gelatin solutions as ordinates over the pH as abscissae, prac- 

 tically identical curves are obtained for the effect of monobasic 

 acids (HCl, HBr, HNO3, and acetic acid) on these properties. 



2. The curves obtained for the effect of H2SO4 on gelatin are much 

 lower than those obtained for the effect of monobasic acids, the ratio of 

 maximal osmotic pressures of a 1 per cent solution of gelatin sulfate 



