302 Messrs. A. Harden and W. J. Young. [ Mar. 6, 
In this last experiment (No. 14) sample (a) was taken at the close of the 
initial period and sample (0) immediately after the cessation of fermentation, 
these points being determined by observation of another sample of the yeast- 
juice. 
It is to be noted that during the fermentation only a small increase occurs 
in the amount of free phosphate (0:075 gramme), while after the cessation 
of fermentation the increase amounts to about three times as much (0°249 
eramme) in approximately an equal time. The total phosphate of the 
original juice was 0°350 gramme per 25 cc. and the amount added was 
0-276 gramme. Since only 0:104 gramme of phosphate remains combined 
at the close of the experiment, it follows that at least 0°276—0:104 = 0-172 
gramme has been regenerated from the hexosephosphate. 
The recurrence of phosphate in these cases appears to be due to the action 
of an enzyme—whether a special enzyme or one of those already known 
to occur in yeast-juice has not yet been determined. 
After yeast-juice containing the sodium salt of hexosephosphoric acid has 
been boiled the amount of free phosphate remains practically unaltered when 
the liquid is incubated at 37°, as is shown by the following experiment. 
Experiment 15.—To yeast-juice containing glucose and an amount of free 
phosphate corresponding to 0°184 gramme of Mg.P20; per 25 c.c. was added 
sodium phosphate equivalent to 0°285 gramme of MgeP20; and the mixture 
incubated at 37° in presence of toluene. A sample was taken at the close of 
the initial period, and as soon as fermentation had almost ceased the whole 
was boiled, the free phosphate estimated and the remainder of the boiled 
liquid preserved at 37°, samples being taken at intervals. 
At the close of the initial period, 25 c.c. yielded only 0°04 gramme of 
Mg2P20;, so that practically the whole of the added phosphate must have been 
converted into a salt of hexosephosphoric acid. At the cessation of fermenta- 
tion the same volume yieided 0-131 gramme of MgeP20;, so that at least. 
0:15 gramme was still present as a hexosephosphate. 
After incubation of the boiled liquid at 37° for an additional 144 hours, the 
amount of free phosphate had only increased to 0°138 gramme, so that the 
action practically ceased when the liquid was boiled. 
(3) Nature of the Chemical Change which occurs in the Fermentation of Glucose 
by Yeast-juice. 
The cycle of changes which is undergone by a phosphate in the presence of 
yeast-juice and glucose appears from the foregoing to be as follows :— 
(1) 2CgH120¢ + 2Re.HPO, = 2CO2 -- 2C2,H,O + CgH1004(PO1R2)2 a+ 2H.0. 
(2) CgHi04(POgRe)o+ 2H.2O a CgHi20¢6+ Diol ie Oa 
