JACQUES LOEB 841 



respond to a difference in the relative volume occupied by equal 

 masses of the two proteins in the same volume of solution. It is 

 generally assumed that these variations of volume of dissolved pro- 

 teins are due to the hydration of the isolated protein ions, but if this 

 view were correct the influence of pH on viscosity should be the 

 same in the case of solutions of gelatin, of amino-acids, and of crys- 

 talline egg albumin, which, however, is not true. 



3. Suspensions of powdered gelatin in water were prepared and it 

 was found, first, that the viscosity of these suspensions is a little 

 higher than that of gelatin solutions of the same concentration, 

 second, that the pH influences the viscosity of these suspensions 

 similarly as the viscosity of freshly prepared gelatin solutions, and 

 third, that the volume occupied by the gelatin in the suspension 

 varies similarly as the viscosity which agrees with the theories of 

 viscosity. It is shown that this influence of the pH on the volume 

 occupied by the gelatin granules in suspension is due to the existence 

 of a Donnan equilibrium between the granules and the surrounding 

 solution. 



