108 



OSMOTIC PRESSURE AND VISCOSITY 



at 20°C. for both sets of experiments. It was noticeable from the 

 first that the osmotic pressure of the gelatin solution which had 

 been kept for 1 hour at 45° and which was therefore supposed to have 

 melted into smaller particles was higher than that of the gelatin 

 solution not previously heated. Fig. 7 shows the result after 22 

 hours. The maximum osmotic pressure was, for the gelatin solution 

 that had been previously heated, 200 mm. H2O, while it was only 

 170 mm. for the other gelatin solution not previously heated to 45°C. 



220 



200 



180 



^160 



cQ 140 

 o 



&.120 



B 



-♦-5 

 o 



a 



O 



100 



80 



60 



40 



20 





 pH 1.8 2.0 2.2 2.4 2.6 2.8 3.0 3.2 3.4 35 3.6 4.0 4.2 4.4 4.6 



Fig. 7. Showing that the osmotic pressure of a solution of gelatin chloride 

 which has been previously heated to 45°C. for 1 hour and then rapidly cooled to 

 20°C. is higher than the osmotic pressure of the same solution of gelatin chloride 

 not previously heated. 



Then the viscosities were determined at 20° and they gave the 

 opposite result (Fig. 8), the viscosities being considerably higher 

 in the solutions not previously heated to 45° than in the solutions 

 previously heated. This experiment then confirms our expectation 

 that there exists a reciprocal relation between the viscosity of protein 

 solutions and their osmotic pressure, inasmuch as a transformation 

 of solid submicroscopic particles of jelly into isolated protein ions 



