Metallic Contact not necessary to the Voltaic Current, 37 



the metals, either in or out of the acid, together, when decom- 

 position of the iodide at jr occurred, but in a reve7'se cnder; 

 for now alkali appeared against the end of the platina wire, 

 and the iodine passed to the zinc, the current being the con- 

 trary of what it was in the former instance, and produced di- 

 rectly by the difference of action of the solution in the paper on 

 the two metals. The iodine of course combined with the zinc. 



883. When this experiment was made with pieces of zinc 

 amalgamated over the whole surface (863.), the results were 

 obtained with equal facility and in the same direction, even 

 when only dilute sulphuric acid was contained in the vessel c 

 (fig. 1.). Whichever end of the zinc was immersed in the 

 acid, still the effects were the same : so that if, for a moment, 

 the mercury might be supposed to supply the metallic contact, 

 the reversion of the amalgamated piece destroys that objection. 

 The use of unamalgamated zinc (880.) removes all possibility 

 of doubt. 



884. When, in pursuance of other views (930.), the vessel c 

 was made to contain a solution of caustic potash in place of 

 acid, still the same results occurred. Decomposition of the 

 iodide was effected freely, though there was no metallic con- 

 tact of dissimilar metals, and the current of electricity was in 

 the same direction as when acid was used. 



885. Even a solution of brine in the glass c could produce 

 all these effects. 



886. Having made a galvanometer with platina wires and 

 introduced it into the course of the current between the 

 platina plate and the place of decomposition t, it was affected, 

 giving indication of currents in the same direction as those 

 shown to exist by the chemical action. 



887. If we consider these results generally, they lead to 

 very important conclusions. In the first place they prove, in 

 the most decisive manner, that metallic contact is not necessary 



for the production of the voltaic current. In the next place 

 they show a most extraordinary mutual relation of the che- 

 mical affinities of the fluid which excites the current, and the 

 fluid which is decomposed by it. 



888. For the pupose of simplifying the consideration, let us 

 take the experiment with amalgamated zinc. The metal so 

 prepared exhibits no effect until the current can pass : it at 

 the same time introduces no new action, but merely removes 

 an influence which is extraneous to those belonging either to 

 the production or the effect of the electric current under in- 

 vestigation (1000.); an influence also which, when present, 

 tends only to confuse the results. 



889. Let two plates, one of amalgamated zinc and the other 

 of platina, be placed parallel to each other (fig. 2.), and intro- 



