•JACQUES LOEB 393 



The second fact which was brought Out was that the relative 

 strength of the apparent attractive and repelling action of the oppo- 

 sitely charged ions of an electrolyte upon the electrically charged par- 

 ticles of water varies with the concentration of the electrolyte in the 

 solution. In the lower concentrations of the electrolyte the attrac- 

 tive action of the anion upon the positively charged particles of water 

 increases more rapidly with increasing concentration of the salt than 

 the repelling action of the cation; while when a certain concentration 

 is reached the repelling action of the cation upon the positively 

 charged particles of water increases more rapidly with a further 

 increase in the concentration of the salt than the action of the anion.^ 



These facts offer an analogy which is helpful in understanding the 

 difference in the action of acids and alkalies on the one hand, and of 

 neutral salts on the other upon the physical properties of proteins. 



When acids or alkalies are added to isoelectric gelatin both ions of 

 the acid or alkali influence the physical properties of proteins but in 

 an opposite direction. When we add acid to isoelectric protein the 

 hydrogen ions increase, the anions depress the osmotic pressure and 

 viscosity of the protein solution (and this depressing action increases 

 with the valency of the anion of the acid). As long as little acid is 

 added to isoelectric protein the augmenting action of the hydrogen 

 ion on these properties increases more rapidly with increasing concen- 

 tration of the acid than the depressing action of the anion; while 

 when the pH of the solution falls below 3.3 or 3.0 the reverse is the 

 case. This causes the drop in the curves for osmotic pressure, 

 viscosity, and swelling below a pH of 3.0. 



When we add allcali to isoelectric protein the OH ions (or the dimi- 

 nution of the concentration of hydrogen ions) increase the osmotic 

 pressure, viscosity, etc., of the solution of metal proteinate while the 

 cation of the alkali depresses these properties with a force increasing 

 with the valency of the cation. In the lowest concentrations of the 

 alkali added the augmenting action of the OH ion on the physical 

 properties of the metal proteinate increases more rapidly with the 

 concentration than the depressing effects of the cation of the alkali; 

 while in higher concentrations, i.e. as soon as the pH becomes about 

 10.0 or 11.0, the reverse is the case.^ 



^Loeb, J., /. Gen. Physiol., 1919-20, ii, 173. 

 ^Loeb, J., /. Gen. Physiol, 1920-21, iii, 85, 247. 



