MR. GROVE ON THE GAS VOLTAIC BATTERY. 
105 
nuous though extremely feeble current ; and the vapours of bromine and iodine, 
were they less soluble, would probably also be found efficient as electro-negative 
gases. 
It now occurred to me that as several of these gases (take as an instance nitrogen) 
were absolutely without effect in the gas battery, this would form a valuable instru- 
ment for the analysis of atmospheric air or other mixed gases. I therefore procured, 
Experiment 24, — Two narrow cubic inch tubes of seven inches long, carefully gra- 
duated into 100 parts. These were immersed in separate vessels of dilute sulphuric 
acid, and filled with atmospheric air exactly to the extreme graduation ; the water- 
mark within the tube was examined when exactly at the same level as the exterior 
surface of the liquid ; folds of paper were used to protect them from the warmth 
of the hands, and thus prevent expansion ; the barometer and thermometer were ex- 
amined, and every precaution taken for accurate admeasurement. One of these tubes 
was left empty in order to ascertain, and eliminate from the result, the effect of solu- 
bility. Into the other was placed a strip of platinized platinum foil, one quarter of an 
inch wide. This strip of foil was connected by a platinum wire with another strip 
placed in a tube of hydrogen and inserted in the same vessel. The apparatus is shown 
in fig. 12. After the circuit had been closed for two days, the liquid was found to 
have risen in the tube a twenty-two parts out of the 100 ; in the tube placed by its 
side, it had risen one division. The tubes were allowed to remain several days 
longer, but no further alteration took place. This analysis gives therefore twenty-one 
parts in 100 as the amount of oxygen in a given portion of air. 
Experiment 25. — The tube a (fig. 12) was charged with nitrogen to a given mark, 
and 0'5 cubic inch of pure hydrogen added, the tube Jl was then charged with oxygen, 
and the circuit closed. Examined after twenty -four hours, the water had risen in 
the tube a exactly 0'5 cubic inch. The apparatus was left in this state for several 
days, but without any further effect ; the voltaic action had thus perfectly exhausted 
the hydrogen and there stopped. 
These experiments are sufficient to prove the accurate eudiometric action of the gas 
battery ; performed on a large scale this method of eudiometry appears to me likely 
to possess some advantages. In the eudiometer of Volta, when gases containing 
oxygen are to be analysed, if the hydrogen added for detonation be impure, the result 
is of course erroneous. The same may be said of the detonation by spongy platinum, 
or by a wire heated by a voltaic current, which I formerly proposed*. 
If, on the other hand, gases containing hydrogen are to be analysed, errors may 
result from any impurities in the oxygen which is added, or from inaccuracy in the 
measurement of either gas ; in the electrolytic method of eudiometry, the quan- 
tity or purity of the hydrogen, in the one case, is of no importance, and in the other, 
the quantity or purity of the oxygen, that is, provided there be sufficient to exhaust 
the equivalent to be abstracted from the mixed gas subjected to eudiometry. 
* Philosophical Magazine, Aug. 1841, p. 99. 
