JOHN H. NORTHROP 



723 



found that the rate of decrease of the viscosity of gelatin solutions 

 also follows the monomolecular formula. This would be expected 

 since the decomposition products have a very low viscosity compared 

 to gelatin. It may be mentioned that the final figure reached by 

 the two solutions was nearly identical and agreed with that found 

 by Van Slyke for the total hydrolysis of gelatin. The alkaline so- 

 lution gave a slightly higher figure due to silicic acid from the glass. 

 Since the gelatin must evidently be destroyed in the very beginning 

 of the reaction, it is this part which must be studied in order to notice 

 any influence of the condition of the gelatin on the velocity of hy- 

 drolysis. It will be noticed that the formol titration increases about 



1.1 



1.0 



>< 09 



3 °^ 



0.7 



Q6 

 Days 



01 



02 



03 



Fig. 2. Increase, with time, in formol titration in strongly aklaline and strongly 

 acid solutions. 



20 times during the reaction so that during the first two or three 

 hundred per cent increase in the original figure the increase will be 

 very nearly linear with respect to time. 



That this is actually the case is shown in Fig. 3 in which the increase 

 in the formol titration, as expressed in per cent of the original figure 

 is plotted against the time. As the figure shows, the curves of all 

 the experiments in which the hydrogen ion concentration was kept 

 constant are straight lines within the limits of experimental error. 

 Curve 4 in which the hydrogen ion concentration decreased during 

 the hydrolysis, however, drops oft" quite rapidly. As will be shown 



