ON THE HYDROLYSIS OF SL'GARS. 273 



„;. , The importance of the kind of acid used was also emphasised by 



\^Lt' Behr, whilst Fleury attempted to trace a connection between the 



' activity ' of an acid in hydrolysing sugar and its molecular dif- 

 fusibility as calculated by Graham. 



The first comprehensive attempt to compare the ' strengths ' of the 

 ,j,oi acids was made by Ostwald, In a much-quoted paper he gave 



& table comparing the 'activity' of acids in inverting sugar 

 with their activity in hydrolysing methyl acetate. There is, indeed, 

 in the case of twenty acids a very fair agreement between the two sets 

 of values. 

 , „„^ Later on in the same year Ostwald published a table comparing 



the electrical conductivities of thirty different acids with their 

 powers of hydrolysing sugar and methyl acetate. The order of the acids 

 as regards their conductivity is the same as their order of activity in 

 catalytic actions, although the agreement is not of a quantitative order. 

 This paper was written to obtain priority over Arrhenius, who was already 

 in this field of inquiry. In the case of weak acids a better proportionality 

 obtains between the conductivity and inverting power, so that in order 

 1 0OP- to explain the lack of proportionality in the case of strong acids 



Ostwald supposed some disturbing eflect to be introduced by the 

 acid itself, similar to the known effect of altering the initial concentration 

 of the sugar. 

 , „„- Koral supplemented Ostwald's table by comparing invertive 



power and conductivity of benzoic and p oxy-benzoic acids. 

 , n^P A similar comparison has been made recently for a series of 



unsaturated aliphatic acids by Fichter and Miiller. 

 , c,qo Gillot also compared the activities of oxalic, tartaric, and citric 



■ acids. His paper, however, contains no new result. 

 , £,„q According to Arrhenius, the divergence of the invertive activity 



of an acid from its electrical activity is to be attributed to a 

 secondary disturbance introduced by the acid — namely, an alteration in 

 the amount of 'active sugar' (Di(/e Section F). It is a significant fact 

 that the 'activity ' of an acid seems to depend to a large extent on the 

 particular interaction which is used as a criterion ; this is well seen in the 

 table given in Section M. 



An interesting point in this connection is the velocity of inversion 

 by a pair of optically antimeric acids, more especially as the enzymes 

 laofi which condition inversion are asymmetrical substances. Emil 

 ibyb. pjggijgp measured the rates of inversion effected at 90° C. by 

 dextro- and Iffivo-camphoric acids ; he found them to be indistinguishable. 

 He justified his experiment on the grounds that, although the conductivity 

 of the two acids is the same and inverting power is known to be pro- 

 portional to conductivity, yet possibly the presence of the optically active 

 sugar might alter the conductivities of the dextro and lajvo acids to a 

 different extent and hence also their invertive powers. It is evident 

 from this that Fischer was inclined to some such explanation of the 

 function of the acid as he has given with such success in the case of 

 catalysis by enzymes. 

 , qj^ - This question was reopened by the author, who has measured 



the inversion of cane sugar by the jG sulphonic acids of dextro- and 

 Isevo-camphor with great care. No difference could be detected between 

 the activities of the two acids in this case either, so that Fischer's result is 

 confirmed. 



1906. T 



