VELOCITY OF REACTION 67 



where it is low will be overcome up to a certain distance from either 

 side, dependent upon the power of the catalyst. A catalyst of 

 sufficient power will carry the reaction up to the same point, in no 

 matter which direction the change is going, this point is what is 

 ordinarily called the equilibrium point or true equilibrium point. But 

 for a less powerful catalyst the diagram shows that there will be two 

 points of equilibrium, one on each side, according to the direction in 

 which the reaction is proceeding, each falling short of the true or 

 absolute equilibrium point. For example, a catalyst which by reason 

 of its properties and concentration has a power represented as at 

 AA', will when the reaction is proceeding in the direction from left 

 to right (X to X') carry the reaction up to the point , and the system 

 will be in equilibrium there, and when the reaction is proceeding in 

 the opposite direction (X ' to X) will carry the reaction up to a 1 , 

 and leave the system in equilibrium there. Hence it is quite 

 erroneous to speak of these equilibrium points in incomplete re- 

 actions as/a/se equilibrium points, for under the given conditions the 

 system is as truly in equilibrium as it would be if all resistance to 

 reaction were removed and it had reached the absolute equilibrium 

 point in the absence of a catalyst. 



Barth, and later Duclaux, found that in the earlier part of the 

 reaction induced by invertase upon cane-sugar, when moderately 

 concentrated solutions were used, that the amount of the sugar 

 hydrolysed was not proportional to its concentration. Thus Barth 

 observed that using the same amount of invertase, and varying 

 the concentration of sugar, that between 5 per cent, of sugar 

 and 15 per cent., practically the same amount was hydrolysed 

 in equal time. Below 5 per cent, the amount hydrolysed increased 

 with the concentration, but not proportionately, so that the per- 

 centage hydrolysed was less, and with percentages higher than 

 15, the absolute amount hydrolysed actually fell off. 1 Duclaux 

 further showed that with the same concentration of enzyme and 

 sugar, the amount hydrolysed up to the point at which 20 per 

 cent, had been inverted was simply proportional to the time, so 

 that the curve representing the progress of the reaction up to 

 this point was a straight line and not a logarithmic curve. At a 



1 This is just the opposite result to that obtained in the case of hydrolysis 

 by acids; here the amount hydrolysed increases more than proportionately 

 to the increase in concentration of the sugar, so that the value of the 

 constant K is increased. ^See E. F. Armstrong, " Proc. Roy. Soc.," 1904, 

 vol. 73, p. 530. 



