GAS BATTERY. 283 



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. 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 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 deu- 

 toxide 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; the 

 residual gas was found to be nitrogen, which thenceforth was 

 gradually increased by hydrogen. The volume of the pro- 

 toxide 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 I 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 



