¢ 
470 Dr A. Harden and Mr. W. J. Young. [Jan. 17, 
less than that caused by an equivalent concentration of arsenate. This 
similarity of the action of arsenite to that of arsenate is shown in the 
experiments summarised below. 
(1) Arsenite produces an acceleration which continues long after an extra 
amount of carbon dioxide equivalent to the arsenite added has been evolved. 
Experiment 24.—Yeast-juice containing 10 grm. of glucose per 100 C.c. 
was incubated until a steady rate of fermentation had been attained. To 
20 cc. of this were added 5 cc. of a 0°3 molar solution of sodium arsenite, 
equivalent to 33°6 ec. of carbon dioxide at N.T.P., and the rate of 
fermentation observed. 
| 
Time after | Rate in c.ce. of carbon Time after | Rate inc.c. of carbon | 
addition, dioxide evolved in Total. addition, dioxide evolved in | Total. 
| in minutes. preceding 5 minutes. in minutes. preceding 5 minutes. 
Po) ee 
ilcre | 25 6 ‘2 32 °8 
7-0 70 30 5°9 38 °7 
Al 14°1 45 5°6 56 °5 
| 6 °2 20 °3 60 5°6 73 °2 
| 6°3 26 °6 85 3°3 89 ‘7 
| 
The total evolved in 85 minutes is thus 89-7 ¢c.c., whereas in absence of 
arsenite it would have been 17 x 1°7 = 28:9, and hence the extra carbon 
dioxide is 89°7 — 28-9 = 60°8, which is largely in excess of the equivalent, 
33°6. 
(2) The acceleration produced by arsenite is senna less than that obtained 
with an equivalent amount of arsenate. 
Experiment 25.—20 c.c. of yeast-juice, containing 2 grm. of glucose, gave 
a rate of 1°7 c.c. in five minutes. The addition of I ec. of a 03 molar 
solution of arsenite raised the rate to 3:1 cc. in five minutes, whilst the 
addition of the same volume of 0°3 molar arsenate to the original juice gave 
a rate of 27°5 c.c. 
(3) The rate attained increases with the concentration of the arsenite 
until a maximum is reached, so that, as in the case ou arsenate, there 1s an 
optimum concentration of arsenite. 
Experiment 26.—Varying quantities of a 0°3 molar solution of sodium 
arsenite were added to 20 cc. of yeast-juice, the total volume being 
maintained at 40 c.c., and containing 10 per cent. glucose. 
(4) The maximum rate attainable and the optimum concentration of 
arsenite are both greater in the case of fructose than in that of glucose. 
