MR. GROVE ON THE GAS VOLTAIC BATTERY. 
Ill 
points were essential to obtaining the effect with certainty ; first, the exclusion of any 
notable quantity of atmospheric air from solution ; and secondly, great purity in the 
hydrogen. In the former case, when the hydrogen could find oxygen to combine 
with, it was not evolved ; in the latter, there would be mixed or rather diluted gas on 
both sides, and the forces would be balanced ; thus I have never succeeded in obtain- 
ing the effect in the open battery, fig. 4, with hydrogen obtained in the ordinary way 
from granulated zinc or iron filings, but have sometimes succeeded with hydrogen 
procured by electrolysis. In the battery fig. 8, I have succeeded in producing the 
effect, but in a feeble degree, from hydrogen obtained in the common way, but have 
never failed with hydrogen obtained by electrolysis. Oxygen of the greatest purity, 
voltaically associated with nitrogen, does not produce a similar effect. The above 
unexpected results render it necessary, in order to ensure accuracy in the eudiometric 
experiment 24, either purposely to use common hydrogen in the batteries figs. 4 and 
12, or what is more expeditious and accurate, to use a battery similar to fig. 8, but 
with tubes longer in proportion to their width ; and having first charged the tubes 
with hydrogen and atmospheric air, to allow these to remain in closed circuit until 
all the oxygen is abstracted and a little hydrogen added, by the electrolytic effect, 
to the residual nitrogen ; then to substitute oxygen for the original hydrogen, which 
will in its turn abstract the hydrogen from the nitrogen and leave only pure nitrogen. 
1 have frequently done this with perfect success. 
Experiment 30. — Hydrogen and carbonic acid in battery fig. 8 produced the same 
effect. The volume of the carbonic acid was increased, and hydrogen was found to 
have been added to it. The effect therefore is not due to any peculiarity of nitrogen, 
but yet some gas is necessary, for experiment 28 proves that hydrogen alone will not 
decompose water. I need scarcely say, that when the above-mentioned effect took 
place an interposed galvanometer was deflected, but the current was much too feeble 
to decompose iodide of potassium. 
I have tried, associated with hydrogen in battery fig. 8, carbonic oxide, olefiant 
gas, protoxide of nitrogen, and deutoxide of nitrogen; the two former produced no 
current or chemical effect, the two latter gave a current and were decomposed. The 
volume of the deutoxide contracted one-half, this was found to be nitrogen, which 
thenceforth was gradually increased by hydrogen. The volume of the protoxide did 
not undergo the previous contraction, except slightly from solubility, but its change 
of state was denoted by the absorption of hydrogen in the associated tube. 
I likewise tried the effect of a vacuum and hydrogen, by charging a battery (fig. 8) 
with 1 cubic inch oxygen and 3 cubic inches hydrogen ; the current was much en- 
feebled by the resistance offered by the vacuum, at first iodide of potassium was de- 
composed and the galvanometer needle whirled round. After twenty-four hours the 
galvanometer needle was only deflected 10°, thus a physical was opposed to, and re- 
sisted, a chemical force ; the current however continued, and all the gas in the oxygen 
tube disappeared, except a minute bubble ; this was probably nitrogen from the atmo- 
