68 EXPERIMENTAL OBSERVATIONS ON 



later stage, as a result according to Duclaux of the retarding 

 action of the products of reaction, the curve began to obey the 

 logarithmic law. Henri later showed, however, that even in this 

 portion Duclaux' s results do not give the logarithmic law, the 

 constant K all the time increasing with the progress of the 

 reaction. 



In an extensive series of experiments on the inversion of cane- 

 sugar by invertase, Henri showed that the value of K calculated 



on the basis K = - log - - continually increased throughout the 

 t a x 



reaction. 



He based, on the fact that the value of the constant increased 

 with the percentage of invert sugar, an empirical formula in which 



/ 3&\ 



the constant K was replaced by K : ( 1 + e - 1, so that the equation 



\ a l 



for velocity of reaction became = e ( 1 + e - ) (a x), leading 



d/t \ CL I 



1 P a / 3? 



on integration to K (1 + e) = log - -flog ( 1 + e - 



t [_ a x \ , 



Calculating the value of the empirical constant e from his experi- 

 mental results, Henri found that it varied within narrow limits 

 around the value unity, and hence the above formula simplifies to 

 1 a + x 



The formula utilised by Henri was that deduced [by 'Ostwald, to 

 satisfy the condition that the products of reaction have an 

 accelerating influence. But the accumulation of products of 

 reaction, or their addition at the beginning of the reaction, in 

 the case of the reaction of invertase upon cane-sugar, as shown 

 experimentally by Henri himself, retard the reaction instead of 

 accelerating it. The formula can hence only be taken as an 

 empirical one, and not as showing that the increase in velocity 

 above the logarithmic value is due directly to the products of 

 reaction. The formula, however, as demonstrated by Henri, gives 

 a close approximation to a constant both for his own results and 

 those of earlier experimenters, and hence is to be preferred to 

 the simple logarithmic formula. 



Henri showed experimentally that the invertin is not attacked 

 or altered during the reaction. He also demonstrated that the 



