THE ACTION OF NEUTRAL SALTS 



107 



swelling of fibrin is, therefore, identical with the influence of 

 salts on the swelling of gelatin. 



The osmotic pressure, viscosity, and swelling of Na gelatinate 

 should be depressed by the cation of a salt and the more so the 

 higher the valency of the cation. Figure 37 shows that this is 

 true for the swelling of Na gelatinate of pH about 9.3. The 

 molecular concentration in which the swelling is depressed by the 



'2048 1C 



Concentration 



FIG. 37. The depressing effect of neutral salts on the swelling of Na gelatinate 

 of pH about 9.3 is due to the cation of the salt, the depressing effect of NaCl being 

 half as great as that of NasSC^ of equal molecular concentration of Na2SO4 while 

 that of CaCh is considerably greater owing to the fact that Ca is bivalent. 



same amount is about half as great for Na 2 S0 4 as for NaCl 

 (for molecular concentrations from M/256 to M/32), while it is 

 about eight times as high for NaCl as for CaCl 2 , roughly proving 

 that the cation is responsible for the depression. The pH of 

 the gelatin was practically the same in all solutions. 



All these data confirm our valency rule, whereby ions of the 

 same valency and the same sign of charge have, in the same 

 concentration, nearly the same depressing effect on osmotic 

 pressure, swelling, and viscosity of proteins; while the depressing 

 effect increases rapidly with the valency. The Hofmeister ion 



