VISCOSITY 



227 



casein dissolved into separate casein ions, was negligible. The 

 curve resembles the 1-hour curve in Fig. 65. After 1^ hours the 

 second measurements of viscosity were taken, and the reader will 

 notice from Fig. 66 that the viscosity had dropped considerably 

 in the neighborhood of pH 2.2 where the solubility of casein chlo- 

 ride is the greatest, and the maximum depression is at pH 2.1 

 where also the solubility is a maximum. With a further lower- 

 ing of the pH the viscosity rises again. The maximal viscosity 

 in the IJ^-hours series is now at pH of about 2.7 or 2.8 where it 



QJD 



FIG. 67. Similarity of curves for log and for relative volume of casein chloride 



770 

 in solutions. 



was also in the 22-hours series in Fig. 65. The later viscosity 

 measurements, after 3 and 6 hours (Fig. 66) confirm these conclu- 

 sions. 



5. It is of interest to see whether or not Arrhenius's formula 

 can account for the influence of electrolytes on the viscosity of 

 casein suspensions. If this were the case, the curves represent- 

 ing log - should run parallel to curves representing the relative 

 770 



volume occupied by the casein in the solution. We get the 

 values of log from our observations of the relative viscosity 



