Mr. Grove on the Gas Voltaic Battery. 431 



oxide of nitrogen ; the two former produced no current or 

 chemical effect, the two latter gave a current and were decom- 

 posed. 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 absorp- 

 tion 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 enfeebled by 

 the resistance offered by the vacuum, at first iodide of potas- 

 sium was decomposed 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 atmospheric air 

 in solution, which had escaped to fill the vacuum. When the 

 stopper was taken out the liquid rose suddenly in the hydrogen 

 tube 2*2 cubic inches, giving the equivalent of the oxygen in 

 the tube and in solution. It is very possible that this ex- 

 periment repeated might sometimes exhibit an evolution of 

 hydrogen in the oxygen tube arising from the escape of the 

 nitrogen of the atmospheric air in solution, and acting as in 

 experiment 29, but I have not seen this effect take place. It 

 should be distinctly understood, that in all the experiments 

 mentioned in this Postscript, except the first part of experi- 

 ment 28, single cells only were used. 



Upon the theory of the experiments 29 and 30 I will ven- 

 ture no positive opinion. That gaseous hydrogen should 

 abstract oxygen from hydrogen, without the latter forming any 

 other combination, is a fact so novel, that any attempted ex- 

 planation is likely to prove premature. If, contrary to the 

 views of Dalton, we suppose that gases when mixed are held 

 together by a feeble chemical affinity, then we may say that 

 the affinity of the nitrogen or carbonic acid for hydrogen pro- 

 duces the effect ; the affinity of the oxygen of the water, being 

 balanced between the hydrogen in the liquid and that in the 

 tube, would enable the resultant feeble affinity of the nitrogen 

 for hydrogen to prevail ; but on this supposition, why does 

 not oxygen produce an analogous effect? Its tendency di- 

 rectly to combine with platinum may indeed be regarded as 

 an opposing force, but this tendency is by many considered 

 hypothetical. On the other hand, it may be called an effect 

 of contact; but this, unconnected with a chemical theory, 



