116 THEORY OF COLLOIDAL BEHAVIOR 



Pauli has done most of his work, but Michaelis and Mostynski 1 

 have pointed out that there is no maximum of viscosity in the case 

 of serum albumin. There is also no maximum in viscosity 

 followed by a drop in the case of egg albumin when the pH varies. 



The hydration hypothesis can be put to a direct test by deter- 

 mining the specific conductivity of solutions of protein salts, e.g., 

 gelatin chloride, albumin chloride, etc. Since according to the 

 hydration hypothesis only the protein ion undergoes hydration, 

 the variation in the osmotic pressure, swelling, and viscosity 

 should be accompanied by a corresponding variation in the 

 concentration of protein ions in solution. If, therefore, the 

 specific conductivity of gelatin chloride is measured at varying 

 pH but equal concentrations of originally isoelectric gelatin, the 

 curves representing the values found for conductivity of the 

 protein should run parallel with the curves for the osmotic 

 pressure, swelling, and viscosity; moreover, the curve for the 

 conductivity of gelatin sulphate should be only about half as high 

 as the curve for the specific conductivity of gelatin chloride; 

 while the curve for the specific conductivity of gelatin oxalate 

 should be almost but not quite as high as that for gelatin chloride. 

 The experiments show that this is not the case. 



The concentration of ionized gelatin in solution can be deter- 

 mined with the aid of conductivity measurements of the solution 

 of a gelatin salt, e.g., gelatin chloride, by deducting the conduc- 

 tivity of the free HC1 in the solution from the total conductivity 

 of the gelatin solution, since the gelatin chloride solution prepared 

 by the writer's method from washed powdered isoelectric gelatin 

 contains practically no other electrolyte except the free HC1 and 

 the gelatin chloride. This was proved by ash determinations 

 and by the fact that a solution of isoelectric gelatin prepared 

 according to our method of washing has practically a con- 

 ductivity of zero. The method of procedure was as follows: 



Solutions of different gelatin-acid salts were prepared in two 

 different concentrations of originally isoelectric gelatin, 0.8 per 

 cent and 2.4 per cent. The specific conductivities of these gelatin- 

 acid salts were determined at different pH. The conductivities 

 of pure aqueous solutions of the same acids at different pH were 

 also measured. In both cases the conductivities were plotted 



1 MICHAELIS, L. and MOSTYNSKI, B., Biochem. Z., vol. 25, p. 401, 1910. 



