740 



ACTIVITY COEFFICIENT OF THE HYDROGEN ION 



results of this series are given in Fig. 7. The pH measurements 

 were made at 25° and calculated to 65° assuming the constant for 

 water as 10"^^ at this temperature and that the hydrogen ion con- 

 centration remains constant up to pH 8.0, and the hydroxyl ion con- 

 centration constant above pH 11.0. The curve is similar in every 

 respect to that for 40°. There seems no possibility, therefore, that 

 the anomalous rate of hydrolysis between pH 2.0 and 10.0 can be 

 due to enzymes or microorganisms. 



It will be noted that the rate of hydrolysis is 10 times more rapid 

 at 65° than at 40° if solutions having the same hydrogen ion con- 



5 



4 



3 

 ?> 2 



1 





 -1 

 -2 

 -3 



+ 1 1 2 3 4 5 6 7 8 9 10 11 12 13 14 

 pH = -(lo^ Ch) 65° 



Fig. 7. Influence of the hj^drogen ion concentration on the velocity of hydroly- 

 sis at 65°C. 



centration at both temperatures are compared, but only 3 times more 

 rapid if solutions having the same hydroxyl ion concentration are 

 compared. This latter value seems remarkably low. A similar pe- 

 cuHarity was noticed by Michaelis and Rothstein^^ in studying the 

 influence of the Cqh on the destruction of pepsin. These authors 

 found that the destruction of pepsin was proportional to the third 

 power of the Coh» and that, if this was taken into account, the tem- 

 perature had no effect on the velocity of the reaction. 



Mechanism of the Reaction. — It was mentioned in the beginning 

 of the paper that the hydrogen ion concentration decreases rapidly 



o 

 o 

 "3 

 > 



o 



25 Michaelis, L., and Rothstein, W., B'wchem. Z., 1920, cv, 60. 



