DEFINITE ELECTROLYTIC ACTION, WITH DIFFERENT SOLUTIONS. 91 



exactly the same quantity of water was decomposed in all the solutions by the same 

 quantity of electricity, though the sulphuric acid in some was seventyfold what it was 

 in others. The strengths used were of specific gravity 1*495, and downwards. 



728. When an acid having a specific gravity of about 1-336 was employed, the re- 

 sults were most uniform, and the oxygen and hydrogen (716.) most constantly in the 

 right proportion to each other. Such an acid gave more gas than one much weaker 

 acted upon by the same current, apparently because it had less solvent power. If the 

 acid were very strong, then a remarkable disappearance of oxygen took place ; thus, 

 one made by mixing two measures of strong oil of vitriol with one of water, gave 

 forty-two volumes of hydrogen, but only twelve of oxygen. The hydrogen was very 

 nearly the same with that evolved from acid of the specific gravity 1-232. I have not 

 yet had time to examine minutely the circumstances attending the disappearance of 

 the oxygen in tliis case, but imagine it is due to the formation of oxywater, which 

 Thenard has shown is favoured by the presence of acid. 



729. Although not necessary for the practical use of the instrument I am descri- 

 bing, yet as connected with the important point of constant electro-chemical action 

 upon water, I now investigated the effects produced by an electric current passing 

 through aqueous solutions of acids, salts, and compounds, exceedingly different from 

 each other in their nature, and found them to yield astonishingly uniform results. But 

 many of them which are connected with a secondary action will be more usefully 

 described hereafter (778.). 



730. When solutions of caustic potassa or soda, or sulphate of magnesia, or sul- 

 phate of soda, were acted upon by the electric current, just as much oxygen and 

 hydrogen was evolved from them as from the diluted sulphuric acid, with which they 

 were compared. When a solution of ammonia, rendered a better conductor by sul- 

 phate of ammonia (554.), or a solution of subcarbonate of potassa was experimented 

 with, the hydrogen evolved was in the same quantity as that set free from the diluted 

 sulphuric acid with which they were compared. Hence changes in the nature of the 

 solution do not alter the constancy of electrolytic action upon water. 



73 1 . I have already said, respecting large and small electrodes, that change of order 

 caused no change in the general effect (715.). The same was the case with different 

 solutions, or with different intensities ; and however the circumstances of an experi- 

 ment might be varied, the results came forth exceedingly consistent, and proved that 

 the electro-chemical action was still the same. 



732. I consider the foregoing investigation as sufficient to prove the very extraor- 

 dinary and important principle with respect to water, that ivhen subjected to the in- 

 fluence of the electric current, a quantity of it is decomposed exactly proportionate to the 



quantity of electricity which has passed, notwithstanding the thousand variations in the 

 conditions and circumstances under which it may at the time be placed ; and further, 

 that when the interference of certain secondary effects (742. &c.), together with the 

 solution or recombination of the gas and the evolution of air, are guarded against, 



N 2 



