430 Mr. Grove on the Gas Voltaic Battery. 



trogen and hydrogen, did not exhibit the effect, thougli suf- 

 fered to remain six weeks, each in closed circuit. 



To ascertain whether the vacuum formed by the abstrac- 

 tion 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 experi- 

 ments, I at length found that two points were essential to ob- 

 taining the effect with certainty; first, the exclusion of any 

 notable quantity of atmospheric air from solution; and se- 

 condly, 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 di- 

 luted gas on both sides, and the forces would be balanced ; 

 thus 1 have never succeeded in obtaining the effect in the open 

 battery, fig. 4, with hydrogen obtained in the ordinary way 

 from granulated zinc or iron filings, but have sometimes suc- 

 ceeded with hydrogen procured by electrolysis. In the bat- 

 tery 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 ni- 

 trogen, does not produce a similar effect. The above unex- 

 pected 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 elec- 

 trolytic effect, to the residual nitrogen; then to substitute 

 oxygen for the original hydrogen, which will in its turn abs- 

 tract the hydrogen from the nitrogen and leave only pure ni- 

 trogen. I 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 peculi- 

 arity of nitrogen, but yet some gas is necessary, for experi- 

 ment 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 cur- 

 rent was much too feeble to decompose iodide of potassium. 



I have tried, associated with hydrogen in battery fig. 8, 

 carbonic oxide, defiant gas, protoxide of nitrogen, and deut- 



