200 



THEORY OF COLLOIDAL BEHAVIOR 



albumin has a comparatively low order of magnitude if 

 compared with the viscosity of solutions of gelatin of the same 

 concentration of protein and the same pH. The viscosity of 

 solutions of crystalline egg albumin of pH 5.1, (i.e., near the 

 isoelectric point) of concentrations from 1 to 14 per cent, was 

 measured at 15C. (Fig. 50). The viscosity is not only low but is 

 also practically a linear function of the concentration. Figure 51 

 gives the viscosity of different concentrations of solutions of 



1.0 



0.5 



1 2 3 4 5 6 7 8 9 10 11 12 13 14 



Concentration of albumin in per cent 



FIG. 50. Viscosity ratio of solutions of crystalline egg albumin near the 

 isoelectric point. Inside the concentrations used, the viscosity ratio is nearly a 

 linear function of the concentration. 



isoelectric gelatin at different temperatures. The solutions 

 were prepared from the same stock solution of isoelectric gelatin 

 and were rapidly heated to 45C. and rapidly cooled to the desired 

 temperature and then the time of outflow in an Ostwald visco- 

 meter was measured. This was done to avoid the increase in 

 viscosity which occurs on standing and which is especially notice- 

 able in the case of solutions of isoelectric gelatin. For the sake of 

 conformity the same procedure was followed in the case of solu- 

 tions of crystalline egg albumin. It is obvious that where the pH 

 influences the viscosity in the same sense as the osmotic pressure, 

 e.g., in the case of gelatin solutions, the viscosity is of a much 

 higher order of magnitude than where the pH has no such influ- 

 ence on viscosity as is the case in solutions of crystalline egg 

 albumin. 



It now remains to show that this difference in the order of 

 magnitude of the viscosity of the two solutions is connected with 

 the relative volume occupied by the protein in solution. The 

 low order of magnitude of the viscosity of solutions of crystalline 



