ON THE STUDY OF HYDKO-AROMATIC SUBSTANCES, 267 



tion with potassium permanganate gives a mixture of dicyclohexane- 

 sulphone and the potassium salt of hex ahydrobenzenesul phonic acid. The 

 free acid crystallises from alcohol, melts at 90° to 92°, and gives a corre- 

 sponding acid chloride anilide and ethyl ester. 



The Hydrolysis of Sugars. By Egbert J. Caldwell, B.8c. 



[Ordered by the General Committee to be printed in extenso.'] 



A. — Introdiictory and Historiccd, 



The hydrolysis of cane sugar by acids, one of the first chemical changes 

 of which the course was followed, is still a most important subject of 

 study in the field of chemical dynamics. A literature is grown up of 

 some 140 papers, dealing with the change from various points of view ; in 

 a large number of cases it is clear the authors have little knowledge of 

 the work which has been published previously. This ignorance has 

 frequently entailed unnecessary reduplication of work, and sometimes it 

 is difficult to reconcile the results of various inquiries. In this report an 

 attempt has been made to bring together all the researches which deal 

 with the hydrolysis of sugar by acids and to discuss the bearing of each 

 paper in its proper place. The moment is an opportune one for such a 

 co-ordination of the literature, in view of the work which is in progress 

 concerning the rate at which hydrolytic change proceeds ; secondly, on 

 account of the prominence now given to theories of solution ; lastly, 

 because of the bearing which the study of such changes has on the 

 problems of osmotic pressure. 



The majority of the researches deal with cane sugar, this being not 

 only an inexpensive pure material but very easily acted upon by acids in 

 comparison with other sugars. 

 1818 Biot, in his first paper on the optical rotatory power of 



solutions, showed that cane sugar is dextrorotatory. He followed 

 2go9 this up by demonstrating that when cane sugar solutions are 



boiled they lose not only their crystallising power but their 

 rotatory power is also diminished, 

 jgoo Biot and Persoz studied the conversion of potato starch into 



dextrin under the influence of dilute sulphuric acid. The optical 

 rotatory power being diminished in this case also, they ai-gued that the 

 change must be taken as an indication of molecular change. Lastly, on 

 1836 J^^u^'^y 11> 1836, Biot announced to the Academy that under 



the influence of acids, aided if necessary by heating, cane sugar 

 loses its crystallising power and is inverted optically, the sign of the 

 rotatory power changing from right to left. 



The inversion of sugar was made the subject of a careful research 

 1850 ^^ Wilhelmy, who showed that the change does not consist in a 



combination of the acid with the sugar, as after removing the acid 

 by precipitation the sugar still remained 'inverted.' The separation of 

 the product into dextrorotatory glucose and lavorotatory levulose was 

 accomplished later on by Dubrunfaut, who formulated the change by the 

 equation 



C.sH^^Oh + H2O = CfiH.aOe + CgH.A 

 Sucrose Glucose Fructose 



Wilhelmy showed that the amount of sugar changed in any given 



