234 



THEORY OF COLLOIDAL BEHAVIOR 



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. Figure 69 

 shows the result after 22 hours. The maximum osmotic pressure 

 was for the gelatin solution that had been previously heated 200 

 mm. H 2 O, while it was only 170 mm. for the other gelatin solution 

 not previously heated to 45C. 



220 



1.8 2.0 2.2 2.4 2.6 2.8 3.0 3.2 3.4 Z.Q 3.6 4.0 4.2 4.4 4.6 



FIG. 69. Showing that the osmotic pressure of a solution of gelatin chloride 

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

 to 20C. 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. 62 of the preceding chapter), 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 sub- 

 microscopic particles of jelly into isolated protein ions and mole- 

 cules diminishes the viscosity but increases the osmotic pressure. 



As far as the quantitative relations are concerned, the differ- 



