62 



COMPARATIVE HYDROLYSIS OF GELATIN 



NaOH 

 8 



o 



y—i 



u 



CI, 



c 



o 



2 



o 



g 



O 



4 











12 3 4 5 



Days at 38° 



Fig. 2. Action of pepsin on gelatin previously partially hydrolyzed by trypsin. 

 500 cc. of 5 per cent gelatin containing 25 cc. of 1.0 M Na2C03 placed at 38°C. 

 and 5 cc. of 10 per cent dialyzed trypsin solution added (pH = 9.5) . 25 cc. pipetted 

 out at intervals and 2 cc. of 4.2 M HCl added (pH = 1.8), and the samples kept 

 at 3° until all had been taken. 5 cc. of 5 per cent pepsin then added to each sample 

 and the samples replaced at 38°. Formol titration was run on 10 cc. The values 

 plotted have been calculated on the basis of 10 cc. of 5 per cent gelatin. 



TABLE I. 



Addition of Pepsin to Gelatin Partially Hydrolyzed by Trypsin. 



Before addition of pepsin 



Increase in titration due to action of pepsin . . 



Formol Titration per 10 cc. of Gelatin Solution. 



1.9 

 2.1 



3.1 

 1.9 



4.8 

 1.1 



7.0 

 0.9 



