A52 Dr. A. Harden and Mr. W. J. Young. [Jan. 17, 
‘separate mixtures were made, each containing 25 c.c. yeast-juice and 
2°5 grm. of glucose, and were incubated until a steady rate of fermentation 
had been attained. There were then added (a) 25 cc. of water and 2'5 grm. 
‘glucose ; (b) 20 cc. of water +5 cc. standard arsenate solution and 2°5 grm. 
glucose. 
The rates of evolution of carbon dioxide were then observed, the apparatus 
‘previously described being employed. 
a b. 
me. | Average rate Average rate 
Total gas. per 5 minutes Total gas. per 5 minutes 
during interval. during interval. 
5 24h eal 23 °3 23 °3 
10 4°9 2°8 47 ‘8 24 °5 
15 8 3 ‘1 72:5 24. °7 
20 10°7 PAPE 99 °5 27 
30 15°9 2°6 154 °1 27 °3 
40 21 °4 2°8 208 °4: 27°15 
50 26 °5 2°55 259 °3 25 *45 
65 34:°5 | PACT 332 °2 24 °3 
95 50 ‘6 | 2°7 459 °O alk 
A striking feature of the effect of the addition of a phosphate to yeast- 
juice is that the marked acceleration only continues until an amount of 
carbon dioxide has been evolved which is chemically equivalent to the 
phosphate added. Moreover, at the close of this period of enhanced fer- 
mentation, the added phosphate is no longer present in a form precipitable 
by magnesium citrate mixture, but has become converted into a hexose- 
phosphate. Neither of these phenomena occurs when an arsenate is 
substituted for the phosphate. The enhanced rate of fermentation con- 
tinues long after an equivalent of carbon dioxide has been evolved, and 
no organic combination of arsenic is formed. 
The first of these statements follows from the results of Experiment 1. 
Here the arsenate added was equivalent to 36 cc. of carbon dioxide in 
the ratio NazHAsO,:COs, whilst the extra carbon dioxide evolved in the 
presence of the arsenate amounted to 4084 cc. in 95 minutes, and the 
rate at the end of that time was still more than seven times that of the juice 
without arsenate. | 
The sharp contrast between the actions of arsenate and phosphate is 
clearly shown when the effects of equivalent amounts of phosphate and 
arsenate on the same sample of yeast-juice are directly compared, as is done 
in the following experiment. 
