ON THE HYDROLYSIS OF SUGARS. 279 



and fructose. From this hypothesis it follows that ' q' ia the heat of ionisa- 

 tion of water plus the heat of ionisation of sugar. Thus : — 



• y ' = 25,000 = Q sugar + Q water = Q sugar + 13.600 

 Heat of ionisation of sugar = Q sugar = 12,000 calories 



Q-j, Kullgren suggested that the effect of temperature on the pro- 



duct CaCjiChCoh)' being the resultant of the separate effects of 

 temperature on the ionisation of water and of sugar, might be calculated 

 if the latter were known. 



,Q^„ Later on he made use of Kohlrausch's conductivity values for 



* water and Madsen's measurements for cane sugar in presence of 



alkali ^ and calculated a temperature coefficient for the inversion velocity 



of the same order of magnitude as the experimental value. 



+ 



Euler objected that KuUgren's 'ions' of cane sugar, H and 

 1904. — 



(CiaHjjO,,), would lead to the result that alkali could cause in- 



+ 



version to take place. The ions must therefore be (C12H21O10) and (OH). 

 , Q^P- Kullgren retorted that if the ions are as supposed by Euler, 



■ acids instead of promoting inversion ought to stop it ! He there- 

 fore falls back upon the original ghccoseions and levuloseions, 



i«QS "^^^ Van't Hoff equation holds not only for the inversion of 



■ cane-sugar but also for the hydrolysis of maltose (Sigmund) and of 

 1 QAi lactose (Armstrong and Caldwell) ; this goes to show that there 



■ must be some kind of ' active part ' in these cases also. 



The latter authors suggest that the ' active part ' should be interpreted 

 as being the sugar molecules which at any moment are in combination 

 with acid molecules. Thus ' g ' is the heat of formation of an active 

 system composed of sugar, acid and a certain number of water molecules, 

 which ultimately decomposes into invert sugar, acid and water {vide 

 Section E). 



G. — Influence of Concentrations of Interacting Molecules. 



G 1. — Concentration of Acid. 



Generally speaking, if the amount of sugar and the volume of the 

 solution be kept constant, the more acid there is present the quicker the 

 inversion proceeds. 

 , QQo It was observed by Urech that as the concentration of the acid 



■ increases, the invertive power increases out of proportion more 

 1SSJ. quickly. He published a curve showing the effect of acid con- 

 centration. The same lack of proportionality between the acid 



1«Rn concentration and the rate of hydrolysis was noted by Ostwald. 



■ The molecular catalytic activity of an acid increases whilst its 

 molecular conductivity decreases, as may be seen from the following 

 table from Ostwald's paper : — 



Inversion of 2(yper-cent. Sugar Solution by HCl. 



_.., , . Molecular Invertive Molecular 



"''"•^'"^ Power of Acid Conductivity 



2 410 294 



10 33-4 326 



100 31-3 384 



' Vide Section E 2. ' That is, considering sugar as an acid substance. 



