Combinatioji "with the ^Icidj^yoduces no Electricity, 131 



the essential principles of the voltaic pile, it forms no part of 

 the phaenoniena at present under investigation*. 



929. If for the oxyacid a hydracid be substituted (927. )> 

 — as one analogous to the muriatic, for instance, — then the 

 state of things changes altogether, and a current due to the 

 chemical action of the acid on the base is possible. But now 

 both the bodies act as electrolytes, for it is only one principle 

 of each which combine mutually, — as, for instance, the chlo- 

 rine with the metal, — and the hydrogen of the acid and the 

 oxygen of the base are ready to traverse with the chlorine of 

 the acid and the metal of the base in conformity with the cur- 

 rent and according to the general principles already so fully 

 laid down. 



930. This view of the oxidation of the metal, or other di- 

 7'ect chemical action upon it, being the sole cause of the pro- 

 duction of the electric current in the ordinary voltaic pile, is 

 supported by the effects which take place when alkaline or 

 sulphuretted solutions (931. 94-3.) are used for the electrolytic 

 conductor instead of dilute sulphuric acid. It was in elucida- 

 tion of this point that the experiments without metallic con- 

 tact, and with solution of alkali as the exciting fluid, already 

 referred to (884.), were made. 



931. Advantage was then taken of the more favourable con- 

 dition offered, when metallic contact is allowed (895.), and 

 the experiments upon the decomposition of bodies by a single 

 pair of plates (899.) were repeated, solution of caustic potassa 

 being employed in the vessel t;, fig. 5. in place of dilute sul- 

 phuric acid. All the effects occurred as before: the galva- 

 nometer was deflected; the decompositions of the solutions of 

 iodide of potassium, nitrate of silver, muriatic acid, and sul- 

 phate of soda ensued at x\ and the places where the evolved 

 principles appeared, as well as the deflection of the galvano- 

 meter, indicated a current in the same direction as when acid 

 was in the vessel v\ i. e. from the zinc through the solution to 

 the platina, and back by the galvanometer and decomposing 

 agent to the zinc. 



932. The similarity in the action of either dilute sulphuric 

 acid or potassa goes indeed far beyond this, even to the proof 

 of identity in quantity as well as in direction of the electricity 

 produced. If a plate of amalgamated zinc be put into a solu- 

 tion of potassa, it is not sensibly acted upon ; but if touched 



* It will, I trust, be fully understood, that in these investigations I am 

 not professing to take an account of every small, incidental, or barely pos- 

 sible effect, dependent upon slight disturbances of the electric fluid during 

 chemical action, but am seeking to distinguish and identify those actions on 

 which the power of the voltaic battery essentially depends. 



S2 



