JOHN H. NORTHROP 



/JO 



300 times more rapidly than that predicted by the formula. The 

 results of a series of experiments covering the range of from pH 

 1.0 to pH 12 are given in Table VIII and Fig. 5. In this figure the 

 black circles are the experimiental points; the line, the graph of the 

 expression, Velocity = 150 (Cjj + 30 Cqh); and the circles, the rate 

 calculated from a formula considered below. It is necessary in this 

 range to use some precaution to prevent the growth of microorganisms. 

 Several different substances were used as indicated in the table. 

 Control experiments were made at 65°C. on the influence of these 



5 



4 



3 



^ 2 



o 1 



> 



o -1 



•-I 



-2 

 -3 



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



pH 40° 



Fig. 5. Influence of the hydrogen ion concentration on the velocity of hydroly- 

 sis at 40°C. 



on the rate of reaction — no significant effect was noted. In the 

 case of HgCl2 the pH was determined electrometrically before adding 

 the HgClo and then colorimetrically. It is a curious fact that nearly 

 all disinfectants poison the hydrogen electrode. The experiment 

 shows that the velocity of hydrolysis is directly proportional to 

 the hydrogen ion concentration from pH 0.65 to pH 2.0. It then 

 decreases much more slowly than the hydrogen ion concentration, 

 passes through a very flat minimum at about pH 6.0 and then in- 

 creases to become directly proportional to the hydroxyl ion con- 

 centration at about pH 10.0. The position of the minimum cannot 

 be told with certainty from the figures given, since the difference 



