1911.] The Alcoholic Ferment of Yeast-juce. 457 
minutes.) 
5 
ee 5 
Maximum rate (c.cs. of 
3 4 5 O : 
0:05 OT 0-2 0:3 O-~: 0-5 06 oO-7 0-8 0-9 I 
c.cs. of arsenate 
The striking feature of the curve is the rapid rise of rate with the con- 
centration, followed by a fall, at first rapid and then gradual. The reason 
for this fall is discussed later on. | 
The smallest amount of arsenate recognisable by a change of rate of 
fermentation in this experiment corresponded with the presence of 
0-11 mgrm. of arsenic in the fermenting liquid. 
Both the optimum amount of arsenate and the maximum rate of fermen- 
tation produced by it vary with the sample of yeast-juice employed, and the 
following numbers illustrate this point :— 
: | Optimum molar 
_ Experiment. | Volume. Juice alone. poe eat Ratio. concentration of 
arsenate. 
c.c. per 5 minutes. 
3°5 36 °5 10 °4 0 °00225 
1:3 14 °2 : 0 °01125 
1°6 
25 ‘ 0 005625 
4, Effect of the Addation of Arsenate on the Total Fermentation produced by 
Yeast-juice. 
When arsenate is added to yeast-juice and sugar, the rate of fermentation 
more or less rapidly reaches the maximum corresponding with the 
