VELOCITY OF REACTION. HETEROGENEOUS SYSTEMS 129 



At higher temperatures, above 25 C., the constant K 

 decreases during the period of reaction, as will be seen 

 from the following figures, which give the mean values of 

 K.icr* during the time intervals 30-90 and 90-180 min- 

 utes. From these an extrapolated value for the time o, the 

 beginning of the reaction, is calculated : 



Temp. 5 10 15 20 25 30 35 40 45 



o min. 7.7 12.5 14.6 20.6 26.6 30.3 40.1 34.4 27.2 



30-90 min. 9.0 12.6 13.7 19.3 24.2 26.6 29.7 19.2 10.5 



90-180 min. 6.3 12.4 15.4 21.9 21.5 22.6 20.4 9.1 3.2 



60 -.- 0.041 0.057 0.130 0*259 0.413 



K has a maximum at about 37 C. This evidently depends 

 upon the rapid destruction of the catalytic agent at higher 

 temperatures. Nicloux has found that at 55 C. its action 

 is totally nullified in ten minutes. This destruction is 

 measured by the decrease of log K during the progress of 

 the saponification, if the process is monomolecular, as 

 indicated by the values found at lower temperatures. At 

 temperatures below 2 5 C. this decrease is insensible; at 

 higher temperatures the destruction of the enzyme proceeds 

 at about double the speed with increase of the temper- 

 ature of 5 C. This corresponds to a value of p = 

 26,000. 



The extrapolated value of K itself at the time o shows 

 a remarkably small increase with temperature. An increase 

 of about 14 C. is necessary to increase it in the proportion 

 2 to i. The value of p calculated from the figures for 10 

 and 30 C. is only 7540. 



This investigation affords a good insight into the real 

 meaning of optima. If we regard the time o, the optimum 



