1 78 Dr. Faraday's Experimental Researches in Electricity. 



sum of the decomposition in the two latter vessels was always 

 equal to the decomposition in the former vessel. But the in- 

 tensity of the divided current could not be the same as that it 

 had in its original state ; and therefore variation of intensity 

 has no influence on the results if the quantity of electricity 

 remain the same. The experiment, in fact, resolves itself 

 simply into an increase in the size of the electrodes (725.). 



727. The third poifit, in respect to which the principle of 

 equal electro-chemical action on water was tested, was varia- 

 tion of the strength of the solution used. In order to render 

 the water a conductor, sulphuric acid had been added to it 

 (707.) ; and it did not seem unlikely that this substance, with 

 many others, might render the water more subject to decom- 

 position, the electricity remaining the same in quantity. But 

 such did not prove to be the case. Diluted sulphuric acid, of 

 different strengths, was introduced into different decomposing 

 apparatus, and submitted simultaneously to the action of the 

 same electric current (714.). Slight differences occurred, as 

 before, sometimes in one direction, sometimes in another; but 

 the final result was, that exactly the same quantity of water was 

 decomposed in all the solutions by the same quantity of electri- 

 city^ 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 results were most uniform, and the oxy- 

 gen and hydrogen (716.) most constantly in the right propor- 

 tion to each other. Such an acid gave more gas than one 

 much weaker acted upon by the same current, apparently be- 

 cause 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 circum- 

 stances attending the disappearance of the oxygen in this 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 describing, yet as connected with the im- 

 portant 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 com- 

 pounds, exceedingly different from each other in their nature, 

 and found them to yield astonishingly uniform results. But 



