110 
MR. GROVE ON THE GAS VOLTAIC BATTERY. 
a sufficient reason for my adding a Postscript containing a few experiments with this 
form of battery, some of which I cannot but consider important. 
Experiment 28. — In order farther to test the opinion expressed, p. 105, six cells of 
this battery were charged with pure hydrogen and dilute acid in the alternate tubes. 
When first charged they decomposed water freely, but after the circuit had been 
closed for a short time, to exhaust the oxygen of the atmospheric air in solution, they 
produced no voltaic effect ; the whole series of six would not decompose iodide of po- 
tassium ; when, however, a little air was allowed to enter any one of the tubes contain- 
ing liquid, that single cell instantly decomposed the iodide ; three cells were put aside, 
each in closed circuit ; at the expiration of a week these produced no effect upon a 
galvanometer, nor was there any gas evolved in the tubes containing liquid ; the 
stoppers were now taken out, and the liquid in the hydrogen tubes rose to an average 
of 0'3 cubic inch; each cell contained a pint, and we may therefore regard 0T5 
cubic inch as the amount of oxygen held in solution by this quantity of acidulated 
water. Were it not for the extreme practical difficulty of perfectly excluding atmo- 
spheric air for a long period, the above would furnish an excellent method of exa- 
mining the quantity of oxygen held in solution by water, and by applying the proper 
calculus we might read off on our galvanometer scale the infinitesimal bubbles of gas 
contained in a given bulk of liquid ; if, however, the acid water or the hydrogen 
contain foreign ingredients, a very different result follows, and the liquid, for reasons 
which will now be obvious, frequently rises considerably in the hydrogen tubes. 
Experiment 29. — I repeated experiment 24 with the battery fig. 8, expecting that 
as the external air was shut out I should obtain the result more speedily ; I was 
indeed not without a vague hope of producing some effect upon the nitrogen. The 
first result did follow ; upon taking out the stoppers the morning after the battery had 
been charged, the liquid rose in the air-tube one-fifth of the gaseous volume. I now 
closed it again and examined it three days afterwards ; a very curious effect had taken 
place ; the volume of the gas in the air tube which had previously contracted had 
now increased , and it continued slowly increasing day after day. I at first believed 
that the nitrogen was decomposed, but after many conjectures and experiments found 
that the increase was due to the addition of hydrogen, a fact to me more extraor- 
dinary than the decomposition of nitrogen would have been. On repeating the ex- 
periment with nitrogen instead of air the same effect took place, but of course without 
the previous contraction. I now returned to battery fig. 4 ; several of these cells 
charged, some with atmospheric air and hydrogen, and others with nitrogen and 
hydrogen, did not exhibit the effect, though suffered to remain six weeks, each in 
closed circuit. 
To ascertain whether the vacuum formed by the abstraction of oxygen from the 
liquid had anything to do with the above effect, a central narrow tube, open at both 
ends, was substituted for the stopper in the battery fig. 8 ; the hydrogen was still 
evolved. Not to detail a tedious set of test experiments, I at length found that two 
