Mr. Grove on the Gas Voltaic Battery. 4-29 



Experiment 28. — In order further to test the opinion ex- 

 pressed, p. 4-23, six cells of this battery were charged with 

 pure hydrogen and dilute acid in the alternate tubes. When 

 first charged they decomposed water freely ; but after the cir- 

 cuit had been closed for a short time, to exhaust the oxygen 

 of the atmospheric air in solution, they produced no voltaic 

 effect; the whole series of six would not decompose iodide of 

 potassium ; when, however, a little air was allowed to enter 

 any one of the tubes containing liquid, that single cell instantly 

 decomposed the iodide ; three cells were put aside, each in 

 closed circuit; at the expiration of a week these produced no 

 effect upon a galvanometer, nor was there any gas evolved in 

 the tubes containing liquid ; the stoppers were now taken out, 

 and the liquid in the hydrogen tubes rose to an average of 0*3 

 cubic inch ; each cell contained a pint, and we may therefore 

 regard 0*15 cubic inch as the amount of oxygen held in so- 

 lution by this quantity of acidulated water. Were it not for 

 the extreme practical difficultyof perfectly excluding atmo- 

 spheric air for a long period, the above would furnish an ex- 

 cellent method of examining the quantity of oxygen held in 

 solution by water, and by applying the proper calculus we 

 might read off on our galvanometer scale the infinitesimal 

 bubbles of gas contained in a given bulk of liquid ; if, how- 

 ever, the acid water or the hydrogen contain foreign ingre- 

 dients, a very different result follows, and the liquid, for rea- 

 sons which will now be obvious, frequently rises considerably 

 in the hydrogen tubes. 



Experiment 29. — I repeated experiment 24 with the battery 

 fig. 8, expecting that as the external air was shut out I should 

 obtain the result more speedily ; I was indeed not without a 

 vague hope of producing some effect upon the nitrogen. The 

 first result did follow ; upon taking out the stoppers the morn- 

 ing after the battery had been charged, the liquid rose in the 

 air-tube one-fifth of the gaseous volume. I now closed it 

 again and examined it three days afterwards j a very curious 

 effect had taken place ; the volume of the gas in the air-tube 

 which had previously contracted had now increased, and it 

 continued slowly increasing day after day. I at first believed 

 that the nitrogen was decomposed, but after many conjectures 

 and experiments found that the increase was due to the addi- 

 tion of hydrogen, a fact to me more extraordinary than the 

 decomposition of nitrogen would have been. On repeating 

 the experiment with nitrogen instead of air the same effect 

 took place, but of course without the previous contraction. I 

 now returned to battery fig. 4 ; several of these cells charged, 

 some with atmospheric air and hydrogen, and others with ni- 



