JACQUES LOEB 49 



curves for osmotic pressure, swelling, and alcohol number should be 

 the reverse for the Ca(N03)2 series as that for Na2S04. On the right 

 side of the isoelectric point (for pH >4.7) gelatin should exist in the 

 form of Ca gelatinate which according to our previous observations 

 has a low osmotic pressure, a low alcohol number, low viscosity, etc. 

 On the left side of the isoelectric point it should exist in the form of 

 gelatin chloride and nitrate in which form gelatin has a high osmotic 

 pressure, swells considerably, has a high viscosity, and a high alcohol 

 number. The forms of the curves actually found are represented in 

 Fig. 3, and show that the facts agree with our theory. 



Our theory finally demands that the two branches of the curve 

 should become almost symmetrical in regard to the isoelectric point, 

 if we add to the HCl a salt with univalent cation and univalent anion, 

 e.g. NaBr. NaBr was added to the HCl solutions so as to make the 

 solution m/16 in regard to this salt, and Fig. 4 gives the curves for 

 gelatin treated with NaBr-HCl. It is obvious that the branches of 

 the curves to both sides of the isoelectric point are much more sym- 

 metrical than was the case in the three other groups of curves. In 

 this case we have on the right side of the isoelectric point Na-gelati- 

 nate, on the left a mixture of gelatin bromide and chloride. On both 

 sides of the isoelectric point we have gelatin in combination with 

 univalent ions, which as we have shown in our previous papers yield a 

 high osmotic pressure, a high swelling, etc. 



The experiments were repeated with other salts, Mg(N03)2, Na2 

 oxalate, etc., and our conclusions were confirmed. In the experi- 

 ments described in this paper the reaction between the anions of the 

 neutral salt with gelatin took place while the gelatin was in the acid 

 solution; while the reaction between the cations of the neutral salt 

 and gelatin could not take place while the gelatin was in the acid solu- 

 tion since all these concentrations were on the acid side of the iso- 

 electric point of gelatin. This reaction must have taken place after 

 the acid treatment and during the process of washing with H2O when 

 the gelatin previously treated with m/256 HCl had reached a pH>4.7. 



This conclusion is confirmed by the experiments in which the gelatin 

 was first treated with acid, then freed from the excess of acid by 

 perfusions with distilled water, and was then treated with a salt and 



