VELOCITY OF REACTION 71 



falls off. These results are similar to those of Barth mentioned 

 above. Similar results with regard to the variation of the hydrolyte 

 in concentration were also obtained for the action of emulsin on 

 salicin. 



In accord with O'Sullivan and Tompson, Henri found that 

 within limits in which the enzyme was not too concentrated the 

 amount of hydrolysis in the case of invertase and cane sugar was 

 directly proportional to the concentration of the enzyme. The 

 laws governing the velocity of reaction have also been studied 

 by Adrian Brown in the case of zymase for conversion of glucose 

 into alcohol, and for the action of invertase upon cane-sugar. In 

 the case of the alcoholic fermentation it was found by this author 

 that the velocity of reaction was not represented by a logarithmic 

 curve, but by a straight line, that is to say, the velocity of 

 reaction was constant. On the other hand, it was found, as in 

 Henri's experiments, that the velocity of reaction in the case of 

 invertase and cane-sugar increased more rapidly than it ought 



on the basis of the logarithmic law, the value of K = - log - 



t a x 



increasing steadily throughout the series. Adrian Brown also 

 obtained similar results to those of Barth, Duclaux, and Henri 

 for variations in concentration of the cane-sugar in not too dilute 

 solutions, the amount converted showing a constant weight and 

 not a constant proportion for equal times. To explain this result, 

 he supposed that a compound is formed between enzyme and 

 sugar which persists for an appreciable time, 1 and that as a result 

 a molecule of enzyme can effect only a limited number of 

 complete molecular changes in unit time. Accordingly, what- 

 ever the available concentration of sugar may be at any given 

 instant, no increase of conversion above a fixed maximum can 

 occur. It is hence only when the concentration of the sugar 

 falls below a certain definite level relatively to the amount of 

 enzyme present that the amount of conversion can fall below 

 this maximum, and the velocity of reaction can begin to obey 

 the logarithmic law. It is hence only in dilute solutions (com- 



1 It is difficult to see why an appreciable time is insisted upon ; all the reason- 

 ing follows whatever be the time-interval of the combination, from an hour to a 

 millionth of a second ; the assumption required really is that the time-interval 

 of the combination shall be constant in all cases, no matter how the concentra- 

 tion varies, 



