Sg a The Alcoholic Ferment of Yeast-jwece. 465 
decomposed than in the absence of arsenate, and that therefore free 
phosphate, which is also a product of the hydrolysis of this compound, must 
also be liberated in greater quantity. Since, moreover, hexosephosphate 
yields two equivalents of phosphate for one of sugar the phosphate must 
accumulate, and accordingly the rate of decomposition of the hexosephosphate 
can also be gauged by the rate of accumulation of free phosphate. 
Experiment 22.—This has been ascertained by estimating the amount of 
free phosphate in the boiled and filtered solutions from Experiment 19. The 
following are the results, expressed in grams of MgeP.0;, the equivalent of the 
arsenate present having been subtracted in each case :— | 
(a) Hexosephosphate-+ arsenate............... 0°6136 
(6) Auto-fermentation + arsenate ............ 01144 
(c) Hexosephosphate without arsenate ...... 0:0707 
Hence, in presence of arsenate, 0°6136—0:0707 = 05429 grm. has been 
liberated more than in its absence, and of this amount 0°5429 — 0:1144 
= 0°4285 grm. has been formed from the hexosephosphate which was added. 
This result is therefore in entire agreement with the observations of the 
rates of fermentation. 
Experiments with zymin confirm the conclusion that the arsenate accelerates 
the action of the hexosephosphatase in an equally striking manner. Zymin 
washed free from soluble phosphates and co-ferment was used, and a solution 
of co-ferment also almost free from available phosphate was added, together 
with an excess of fructose. This mixture was almost incapable of producing 
fermentation, owing to lack of phosphate, and as a matter of fact gave a 
total of only 1°5 cc. of carbon dioxide, whereas when phosphate was added as 
much as 132 ¢.c. were involved. Solutions of hexosephosphate were added to 
two equal volumes of this mixture, and to one of these arsenate was also 
added. The sole source of phosphate in these two liquids was the hexose- 
phosphate, and the rate of fermentation would therefore be controlled by the 
rate of production of phosphate from this. Any increase of fermentation in 
the presence of arsenate must therefore be due to the accelerating action of 
this salt on the hexosephosphatase. 
Experiment 23.—The zymin and co-ferment solution were prepared in the 
same manner as those used in Experiment 17. 
1. 10 cc. zymin suspension + 15 ec. co-ferment solution + 0°5 grm. 
fructose + 8°8 c.c. of 0°14 molar hexosephosphate + 0:2 c.c. arsenate. 
2. The same mixture but containing 0°2 c.c. of water instead of arsenate. 
Here the rate of fermentation, and consequently of hydrolysis of hexose- 
phosphate, in presence of arsenate is about doubie that in its absence. 
