MODIFICATIONS OF MILK-SUGAR. 



29 



TABLE VIII. CHANGE OF ROTATION OF a-MiLK-SuGAR IN 

 SOLUTION. 



The solution used was examined in a 198-4 mm. tube using 

 sodium light ; two determinations gave 7-090 and 7-072 per 

 cent, of anhydrous milk-sugar, and, as the solution had a density 

 of 1-0265 at 17 (the temperature of observation), it contained 

 7-651 grammes of hydra ted milk-sugar per 100 c.c. 



It is seen that the rotation is approximately constant for the 

 first 6 minutes, and averages 12-75, which corresponds to 

 [a]p = 83-99. After 24 hours the rotation is constant at 7-95, 

 which corresponds to [a] D = 52-37. 



The figures given in the " calculated " column are deduced by 

 the formula 



lo glo (R T -Roc) = 0-68124-0-00491 (T-6). 



The fact that the fall in rotation is expressed by a logarithmic 

 curve shows that the rate of change is proportional to the amount 

 of unchanged substance in solution ; this is Harcourt's law of 

 mono-molecular change. 



The ratio between the initial rotation and the final rotation, 



which may be called the bi-rotation ratio, is 



83-99 

 52-37 



= 1-604. 



The mean of several determinations has led to the value for 

 [a]n of the hydra ted a-modification = 84-0, and the bi-rotation 

 ratio 1-6 ; these are the figures given by Schmoeger, who, how- 

 ever, assigned to them an approximate value only. 



The small amount of thermal change during change of rotation 

 and absence of change in destiny and freezing point show, with 

 a considerable degree of probability, that the change manifested 



