250 Mr. A. Compton. Optimum Temperature of 



containing 4, 8, 12, 24, and 40 mgrm. dissolved in 10 cm. 2 of water, which, 

 after standing for half to one hour, were introduced in portions of 1 cm. 3 

 into five series of test-tubes containing 286 mgrm. of salicin and 4, 9, 14, 29, 

 and 49 cm. 3 respectively of water. After 15 hours' incubation in baths 

 at known temperatures the action was stopped and the quantity of salicin 

 hydrolysed in each tube estimated as before. The numbers obtained are 

 given in Table IV. 



Table IV. 



Temperatures at the 

 beginning and end of 

 each experiment. 



Salicin hydrolysed per cent, with the following substrate 

 concentrations : — 



M/5. 



M/10. 



M/15. 



M/30. 



M/50. 



o 



7 "3- 7 -7 





10 -s 









8 - 3- 9 - 



6 "6 











9 - 6- 8 "5 







18 "3 







9 '4-10 - 8 



— 



— 





26 -0 





12 '0-10 - 9 











35 -5 



17 - 2-17 - 3 





23 -0 









17 - 4-17 - 1 



10 -8 











17 -5-17 -6 







32 -5 







18 -6-18 -5 











57 '5 



18 -9 









47-0 





25 -2-25 -0 









63 7 





26 -4-25 -7 











75 -0 



26 -5 



19 -2 



38 -6 



50 -8 







30 -0 



22 -3 



41 -9 



58 -5 



75 -3 





30 -5 











75 -8 



33 5 



23 -6 



44 -6 



62 -9 



80 -7 



88 -3 



40-5 









68 -3 



76 7 



40 -7-40 "6 





39 -4 









40 -8-40 -7 



22 -4 





55 -2 







45 -0-45 -2 











56 -9 



45 -5-45 -3 



19 -7 



35 -0 



43 -7 







45 "5 









54 -7 





50 -3-50 -5 



15 -1 





31 -9 







50 -6-50 -5 





25 -8 









51 -1-50 -8 









34 -3 





51 -5-51 -2 











38 -3 



54 -3-54 -0 



11 -2 











54 -2-54 "3 





18-4 



21 -4 



24-3 





54 -6-55 -0 











25 -8 



These numbers give graphically the curves shown in fig. 4 (p. 249). 



On examination the above curves indicate, although with very different 

 degrees of precision, maxima in the same region of temperature. In so far 

 as the curves are comparable with one another, they produce the general 

 impression that the optimum temperature of the enzyme is constant, and 

 consequently independent of the concentration of the substrate. But to 

 answer the question more definitely curves of a uniform type, easily com- 



