THE STABILITY OF PROTEIN SOLUTIONS 



257 



is due to the anion. Hence, the precipitating effect of CaCU on 

 gelatin chloride is about the same as that of a NaCl solution of 

 the same concentration of Cl ions. 



When the gelatin ion has a negative charge, e.g., in the case of 

 Na gelatinate, the depressing effect of neutral salts on the P.D., 

 osmotic pressure, or swelling of the gelatin solution is due to the 



4096 2048 IU2? 5IZ 256 125 



Concentration of salt solution 



FIG. 76. Depressing effect of salts (NaCl and Na 2 SO 4 ) on P.D. and on osmotic 

 pressure of a 1 per cent gelatin chloride solution of pH 3.5. 



cation of the neutral salt and increases rapidly with the valency of 

 the salt. This is illustrated in Fig. 37, p. 107, which expresses 

 the effect of neutral salts on the swelling of Na gelatinate of a pH 

 of about 9.3. It is obvious that in order to depress the original 

 volume of the Na gelatinate to one-half a M/512 solution of 

 CaCl 2 and a M/16 solution of NaCl and about M/32 solution of 

 are required. In other words, the depressing action of 



17 



