Definite Electrolytic Action, with different Solutions. 179 



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 sulphate of soda, were acted upon by the elec- 

 tric 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 sulphate of ammonia (554.), or a solution 

 of subcarbonate of potassa was experimented with, the hydro- 

 gen 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. 



731. I have already said, respecting large and small elec- 

 trodes, 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 experiment might be varied, the results came forth ex- 

 ceedingly consistent, and proved that the electro-chemical 

 action was still the same. 



732. I consider the foregoing investigation as sufficient to 

 prove the very extraordinary and important principle with 

 respect to water, that when subjected to the ztifluence of the 

 electric current, a quantity of it is decomposed exactly propor- 

 tionate to the quantity of electricity which has passed, notwith- 

 standing the thousand variations in the conditions and circum- 

 stances 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, the products of 

 the decomposition may be collected with such accuracy, as to 

 afford a very excellent and valuable measurer of the electricity 

 concerned in their evolution. 



733. The forms of instrument which I have given, flgg. 

 9, 10, 11. (709. 710. 711.), are probably those which will be 

 found most useful, as they indicate the quantity of electricity 

 by the largest volume of gases, and cause the least obstruc- 

 tion to the passage of the current. The fluid which my pre- 

 sent experience leads me to prefer, is a solution of sulphuric 

 acid of specific gravity about 1*336, or from that to specific 

 gravity 1*25; but it is very essential that there should be no 

 organic substance, nor any vegetable acid, nor other body, 

 which, by being liable to the action of the oxygen or hydro- 

 gen evolved at the electrodes (773. &c), shall diminish their 

 quantity, or add other gases to them. 



2 A2 



