118 



THEORY OF COLLOIDAL BEHAVIOR 



to account for the low osmotic pressure of gelatin sulphate solutions 

 by the hydration hypothesis, the specific conductivity of gelatin 

 sulphate should be half or less than half of that of gelatin chloride, 

 while the curve for gelatin oxalate should be almost as high as 

 that for gelatin chloride. Figure 38 shows that neither expec- 

 tation is fulfilled. 



\ 



50 



PH 20 22 Z4 26 2.6 3.0 3.2 3.4 3.6 3.8 4.0 42 4.4 4.6 46 5.Q 

 FIG. 39. Comparison of conductivity curve and osmotic, pressure curve for 

 albumin chloride, showing the entirely different character of the two curves. 



Figure 39 shows that the same disagreement exists between the 

 conductivity curve and the osmotic pressure curve for solutions 

 of the chloride of crystalline egg albumin. These curves, then, 

 do not support the hydration hypothesis. 



Pauli's hydration theory rests, as stated above, on an assump- 

 tion made by Kohlrausch that the difference in the mobility of ions 

 is due to molecules of water being dragged along with the migrat- 

 ing ion. Lorenz, 1 Born, 2 and others have come to the conclusion 

 that while Kohlrausch's idea is probably correct for monatomic 

 ions it cannot be correct for large polyatomic ions. This would 



1 LORENZ, R., Z. Elektrochem., vol. 26, p. 424, 1920. 



2 BORN, M., Z. Elektrochem., vol. 26, p. 401, 1920. 



