1911. ] The Alcoholic Ferment of Yeast-juice. 455 
2. The Products of Fermentation in Presence of Arsenate. 
In order to ascertain whether the reaction which occurred in the presence 
of arsenate was the normal decomposition of sugar into alcohol and carbon 
dioxide, the ratio of these products was determined for an arsenate 
fermentation. 
Experiment 5.—75 cc. of yeast-juice were incubated with 8 germ. of 
glucose and 15 cc. of 0°1 molar sodium bicarbonate solution in order to 
remove all free acid and free phosphate. In one portion of this the alcohol 
was estimated at once by distillation. To each of two other equal portions, 
1 ec.c. of arsenate solution was added, and both were incubated at 25° for 
15 hours. During this period 185°3 c.c. of pure carbon dioxide, measured 
moist at 20°8° and 763°6 mm., were evolved, weighing 0°3303 erm. At the 
end of this time the total alcohol was estimated in one of the portions, and 
the alcohol produced in presence of arsenate thus ascertained by subtracting 
that originally present. The following were the results :— 
| Before incubation. | After incubation. Difference. | Ratio. 
ee | 0 4898 0°7924, | 03026 eae 
Carbon dioxide ...... | O 0 °33038 0 3303 
The theoretical ratio is 1°04. The value obtained agrees well with the 
ratio previously found by similar methods for the normal fermentation of 
glucose by yeast-juice. 
3. Lffect of the Concentration of Arsenate on the Maximum Rate of Fermentation 
Atiainable. 
The rate attained increases with the concentration of arsenate until a 
certain limit is reached. A further increase beyond this point diminishes 
the rate of fermentation, so that just as in the case of phosphate there is a 
certain optimum concentration of arsenate, corresponding with which there 
is a maximum rate of fermentation. 
In carrying out these estimations of rate of fermentation, a mixture of 
glucose with yeast-juice, 10 grm. to 100 cc. was incubated until the 
rate of evolution of carbon dioxide had become constant, and all free 
phosphate had been converted into hexosephosphate. The standard sodium 
arsenate solution (0°3 molar), containing 10 grm. of glucose per 100 cc. 
and saturated with carbon dioxide at 25°, was then added in the desired 
quantity. Since sodium arsenate solution after saturation with carbon 
dioxide contains an equilibrium mixture of the two arsenates and sodium 
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