165 
1893-94.] Dr Robertson on Fermentation of Sugars. 
A consideration of these figures shows that with — 
1. Cane Sugar a considerable time elapses before the commence- 
ment of its change into lactic acid. It is only after the 
fourth hour that fermentation begins, and proceeds slowly at 
first, though after the thirtieth hour the change is rapid and 
extensive. 
2. Invert Sugar and the rest of the sugars experimented with, 
have no resting period like cane sugar, but begin to ferment 
at once. Up to the thirtieth hour the change which invert 
sugar undergoes is much more rapid than in the case of cane 
sugar, but after this period they closely correspond. 
3. Lactose undergoes a feeble degree of change up to the Uventy- 
fourth hour, after which time, however, the change becomes 
very rapid. 
4. Dextrose during the early hours undergoes a slowly progressive 
fermentation. Later, it becomes rapid, and at the fourth 
day this sugar has undergone a greater degree of change than 
any of the other sugars with the exception of Isevulose. 
5. Maltose is apparently less easily and less rapidly fermented 
than dextrose. Up to the twenty-fourth hour it resembles 
lactose, but not afterwards, as at the seventy-second hour the 
latter has yielded almost twice as much lactic acid as the 
former. 
6. Lcevulose undergoes marked fermentation. Dextrose is 
much more rapidly changed by the alcoholic ferment than 
laevulose ; but it is precisely the reverse when these sugars 
are subjected to the lactic acid fermentation. The fermenta- 
tion of Isevulose by the lactic ferment is remarkable in that 
it yields about five times as much lactic acid as is yielded by 
any of the other sugars in the same period of time. 
in causing inversion). It was then kept at a temperature of 170°-180° F. in a 
water bath for two hours. After cooling, the loss by evaporation was replaced, 
and it was rendered neutral by adding a few drops of caustic potash solution. 
This invert-sugar solution is usually said to consist solely of equal parts of 
dextrose and Isevulose ; this, however, is denied by other chemists, as Petit 
and Maumene. 
