34 VELOCITY OF REACTIONS 



if the concentration of the sugar is ^-normal, c = i 

 indicates 342 grammes per litre. 



<r = 0-OI 0-025 0-05 O-I 0-25 05 I 1*5 2 



« = o»58 1-41 2-40 2-96 4*65 5-04 4-45 2-82 1-15 



As will be seen from these figures, n is at first 

 nearly proportional to c, then it slowly reaches a very 

 flat maximum at c about = 0-5 normal, and subse- 

 quently falls at very high concentrations, at which 

 the solvent may be regarded as changed. Adrian 

 J. Brown has reached similar results. 



In general chemistry we are accustomed to find 

 that the transformed quantity is proportional to the 

 concentration of the reacting substance, as is the 

 case in the figures above, when c does not exceed 

 0-03 normal or about 1 per cent. But this is not at 

 all true at higher concentrations. It has been found 

 that this peculiar effect is due to the formation of a 

 compound of the invertase with the sugar or its 

 products of decomposition. The compound, into 

 which the cane-sugar enters, is really the substance 

 subject to decomposition. With small quantities of 

 sugar (and not too insignificant quantities of enzyme) 

 the quantity of the compound is proportional to the 

 concentration of the sugar ; later on the said quantity 

 tends to a maximum, dependent on the quantity of 

 enzyme present. Therefore also the quantity of sugar 

 decomposed in one minute tends to reach a flat 

 maximum as is also indicated by the observations. 



Michaelis and Menthen have investigated this 

 question very thoroughly, and found that all observa- 

 tions are in good agreement with the hypothesis here 



