JACQUES LOEB 



99 



pressure, the observed osmotic pressure being due to the isolated ions 

 of the 0.5. per cent gelatin in solution which determine the Donnan 

 effect, and in addition, to the gas pressure of the isolated gelatin 

 ions and the isolated gelatin molecules. Theoretically, of course, the 



(9 



zi 



CD 



a 

 o 



O 



500 

 475 

 450 

 425 

 400 

 375 

 350 

 325 

 300 

 275 

 250 

 225 

 200 

 175 

 150 

 125 

 100 



75 



50 



25 

 pH 1.6 1.8 2.0 2.2 24 2.6 28 3.0 3.2 3.4 3.6 3.8 4.0 42 44 46 



Fig. 1. A suspension of 1 gm. of a fine powder of gelatin in 100 cc. of water 

 has practically no osmotic pressure (lowest curve), while a solution of 1 gm. of the 

 same gelatin has a maximal osmotic pressure of over 500 mm. (uppermost curve). 

 A mi.Kture of 0.5 gm. of powdcrccl and 0.5 gm. of liquid gelatin in 100 cc. water 

 has practically the osmotic pressure of the 0.5 per cent liquid gelatin in 100 cc. 

 of water (middle curve). 



