532 Dr. E. F. Armstrong and Mr. E, J. Caldwell. [Apr. 5, 



Table VIII. — 18 per cent. (0*5 gramme molecule) Milk Sugar, 

 0*25 gramme molecule H 2 S0 4 . Temperature 60° -1. 



Per cent. 10 4 , a 



Time in hours. an. hydrolys^d. ~f~ ^ZT X ' 



19°-37 ' 0-0 — 



6 19-73 6-5 0-81 



17 29-22 15-4 0-71 



42 21-50 38-5 0-84 



66 22-38 54-5 0-86 



90 23-00 65-7 0-86 



140 24-02 84-2 0-96 



Complete change 24-89 



Mean 0'84 



K = 1-68. 



In a second experiment a value K = 1-70 was obtained. 



The value for K thus arrived at is much smaller than that deduced 

 from the experiments with chlorhydric acid ; but if the comparison 

 be made for acids of the same molecular strength the results are nearly 

 identical, since 2K = 2x 1-69 = 3*38. 



It will be noticed that in this instance there is little or no evidence 

 of reversion. 



Influence of Temperature. — We have determined the rate at which 

 milk sugar undergoes hydrolysis at different temperatures in order to 

 be able to contrast its behaviour in this respect with that of other 

 sugars. The following table gives the values of K at three tempera- 

 tures obtained on hydrolysing a solution containing 0'5 gramme- 

 molecular proportion of milk sugar by means of a 0*5 gramme-molecular 

 proportion chlorhydric acid. 



Temperature. K. 



60°-l 3-53 

 74-1 25-05 

 99-0 (approx.) 334 -2 



It is apparent from these numbers that an increase of about 

 14 per cent, in the value of K takes place per degree and that the rate 

 of hydrolysis of milk sugar is even more influenced by temperature 

 than is that of maltose. The difference is better seen on comparing 

 the constants calculated for each sugar from Arrhenius's temperature 

 equation. 



Sugar. • Acid. q[2« 



Cane sugar HC1 12,820* 



Maltose HC1 I7,127f 



Milk sugar HC1 19,105 



H 2 S0 4 18,424 



* Arrhenius, loc. cit. 

 f Sigmondj loc. cit. 



