Concentration upon the Optimum Temperature of a Ferment. 415 



centration of the medium must, in accordance with fig. 1, be attended by- 

 disablement of the enzyme ? Fig. 3 answers tbese questions. 



Fig. 3, as expected, also shows a series of curves of varying altitudes ; and, 

 as before, a perfectly definite optimum temperature is seen to characterise 

 each hydrogen ion concentration studied. But here an unlooked-for 

 result is discerned. For H + concentrations situated between the optimum 

 and the natural reaction the optimum temperature rises still higher, to 

 fall again as the natural reaction is overreached ; the rise in the optimum 

 temperature passes by an optimum value. This is evident from the locus 

 curve drawn through the maxima of the several optimum temperature 

 curves figured in fig. 3 ; and it is still better seen in fig. 4. where a curve 

 is plotted with the various optimum temperatures recorded in figs. 2 and 

 3 as ordinates, and the corresponding amounts of acid and alkali present in 

 the reaction mixttrre as abscissa?. 



OA 0\5 04 03 OZ Oi O Ol 0-2 



CN5 pec 5CM 3 reaction mixture 



An optimum temperature of +49° thus seems possible in a reaction 

 mixture containing - 032 cm. 3 M/100 H 2 S0 4 . But it might be supposed 

 that this is the optimum reaction of the ferment for that temperature, 

 since, in accordance with the work of O'Sullivan and Tompson* on the 

 enzyme sucrose, the optimum reaction of that ferment is known to depend 

 on the temperature serving for its determination ? This question it is 

 proposed to investigate. 



To illustrate in a striking way the essential fact established by the 

 investigation, that the optimum temperature of the enzyme depends largely 

 on the hydrogen ion concentration of the medium, it is only necessary 

 to reproduce side by side on the same diagram the optimum temperature 

 curve from fig. 3 corresponding to the natural reaction and that from fig. 2 



* 'Chem. Soe. Journ.,' vol. 57, p. 859 (1890). 



