174 



THEORY OF COLLOIDAL BEHAVIOR 



(a) The curve for the calculated osmotic pressure of gelatin 

 chloride is identical with the curve for the calculated osmotic 

 pressure of gelatin phosphate, and the same is true for the two 

 corresponding curves representing the observed osmotic pressures 

 (Figs. 43 and 44). 



pH 1.4 1.6 IB 2.0 22 2.4 2.6 2.8 3.0 3.2 3.4 3.6 3.8 40 42 4.4 46 45 



FIG. 44. Observed curves representing the influence of pH and valency of 

 anion on osmotic pressure of solutions in gelatin-acid salts containing 1 gm. of 

 originally isoelectric gelatin in 100 c.c. solution. The curves for gelatin chloride 

 and gelatin phosphate are identical since the anions, Cl and HzPC^, of these two 

 gelatin salts are monovalent. The curve for gelatin sulphate is less than half as 

 high as the curve for the two other salts because the anion of gelatin sulphate is 

 bivalent. Both curves rise from the isoelectric point at 4.7 to a maximum at pH 

 about 3.4 or 3.5, and then drop rapidly again. 



(6) The curve for the calculated osmotic pressure of gelatin 

 sulphate is a little less than half as high as the curves for the calcu- 

 lated osmotic pressures of gelatin chloride and gelatin phosphate; 

 and the same is true for the curves representing the observed 

 osmotic pressures of gelatin sulphate and gelatin chloride. 



