58 INFLUENCE OF TEMPERATURE 



from the diagram (Fig. 12 c), representing observa- 

 tions of Nicloux, made 30, 90 and 180 minutes after 

 the mixing of the cotton oil and the lipase. The 

 mean velocity of reaction calculated from these 

 figures corresponds to about 60 and 135 minutes. 

 The optimum falls at about 33° and 30° C. respec- 

 tively at the two times of observation. From this 

 observation it is quite clear why different authors 

 give different values for the optimum temperature. 

 They have not observed the influence of the time 

 of heating. If this time were zero (which is im- 

 possible to realise) we would not observe any 

 optimum. As is seen from the different curves 

 of log K or K (this last for Nicloux's figures) the 

 fall of the K-curve is exceedingly rapid when the 

 temperature rises above the optimum one. 



Regarding vital processes, it may be observed that 

 the chief substance of living cells, the protoplasm, 

 generally suffers at temperatures above 40° C. and 

 in most cases is killed above 55° or 6o° C. Hence it 

 is obvious that vital processes become hampered 

 by temperatures above about 40° C. A similar 

 remark may be made regarding low temperatures. 

 At about zero the aqueous solutions in the cell 

 freeze and the life - processes are brought to a 

 standstill. But even if freezing does not occur 

 the vital processes are much hindered in the 

 neighbourhood of zero. 



As a general result of our investigation we may 

 say that the influence of temperature on the velocity 

 of different processes in which enzymes, organic 



