10 



The optimum varies with the time of observation. Extra- 

 polation of the time-curves in order to obtain the values 

 after o time, did not give the values which should be 

 obtained if B 1 a c k m a n's theory applied fully. Finally 

 mention must be made of a publication v^hich appeared 

 in 1910, by Van 1 1 e r s o n and Miss van Amstel, 

 wherein the considérations of Blackman are submitted 

 to a renewed investigation. The question was put, whether 

 or not the dependence on température ofalcoholic fermen- 

 tation and of the action of invertase on cane-sugar was 

 in agreement with van 't H o f f's law. The writers conclude, 

 that van 't Hoff's law does not apply to this case and 

 hence their first conclusion runs : „it should thus be 

 pointed out very emphatically that even on account of 

 the course of the optimum-curve below harmful tempéra- 

 tures the theory of D u c 1 a u x and Blackman must 

 be rejected." 



In this investigation the reaction-velocity after a warming- 

 time of minutes was determined on différent lines and 

 the resuit obtained by the authors is „that the curve 

 which refers to a preliminary warming-time of minutes 

 is a pronounced optimum-curve, as well in the case of 

 alcoholic fermentation as in that of the inversion of 

 sugar." — „The opposite results at which Blackman 

 arrived and with reserve Kuyper too, are in our opinion 

 due to the fact, that the velocity of the physiological 

 reactions measured by thèse investigators, was small 

 compared to the velocity with which the subsidence 

 took place." 



In Chapter III, when discussing my own results, I will 

 again return to thèse investigations, especially to the 

 last mentioned. 



