474 Dr. A. Harden and Mr. W. J. Young. [Jan. 17, 
from phosphate+0°5 grm. of fructose+9 cc. of hexosephosphate solution 
+1 c.c. of water, on addition of— | 
(1) 1 cc. water gave 9°5 c.c. of carbon dioxide in 25 minutes. 
(2) 1 cc. of 03 molar arsenite solution gave 1171 c.c. in 25 minutes. 
In this case the rate was only increased about 20 per cent., whereas the 
addition of arsenate doubled the rate. 
9. Inhibitory Action of Arsenate and Arsenite. 
Both arsenate and arsenite may exert an inhibitory action on alcoholic 
fermentation, and this may manifest itself in two ways. If a sufficient 
excess be added, no fermentation at all occurs; in presence of a smaller 
amount than is necessary to produce this total inhibition, the effect 1s mani- 
fested by the low rate and shortened duration of fermentation. An experi- 
ment showing this behaviour of arsenate in a typical manner has already 
been quoted (No. 11). Even when the rate of fermentation is considerably 
increased by the presence of an amount of arsenate in excess of the optimum 
amount, it frequently happens that this rate falls very rapidly and that all 
fermentation ceases in an hour or two. The exact conditions under which 
this occurs have, however, not been ascertained. It is as yet uncertain 
whether this inhibitory action is due, as suggested by Buchner, to changes 
in the colloidal state of the fermenting complex or to the formation of 
inactive combinations of the complex with the arsenate and arsenite, in a 
similar manner to that suggested by the authors in the case of inhibition 
produced by excess of phosphate.* In all probability the phenomenon is a 
complex one in which several factors participate. 
The total inhibition produced by arsenite which was observed by Buchner 
(p. 469) with juice which had been submitted to dialysis, evaporation, etc., 
may not improbably be ascribed to a loss of fermenting complex during these 
operations, so that the amount of arsenite added was greatly in excess of the 
optimum. It is, however, quite possible that the proteins accompanying the 
ferment present in the juice do exert a protective influence, as suggested by 
Buchner, and that a diminution in their amount may also play some part in 
the phenomenon. 
10. Experiments with Various Salts. 
No other salts capable of bringing about results in any way comparable — 
with those produced by arsenates and arsenites have been found. Experi- 
ments with the sulphate, orthovanadate, antimonate, tungstate, chromate, 
stannate, phosphite, and citrate of sodium, and with tartar emetic and zine 
sulphate, were all negative. 
* “Roy. Soc. Proc.,’ B, 1908, vol. 80, p. 299. 
