Action of Iron upon Solutions of some Metallic Salts, 275 



paper, if I produce a new case bearing evidence in favour of 

 the theory*, according to which voltaic electricity is due to 

 chemical action. It is true that the beautiful researches of 

 Mr. Faraday, as well as those of Mr. De la Rive, have led to 

 results which remove from an unbiassed mind even the shadow 

 of a doubt on the subject, and which prove in the most satis- 

 factory manner, that mere contact of heterogeneous metals is 

 not capable of disturbing their electric equilibrium. Still, 

 as the number of philosophers is as yet rather considerable 

 who maintain the hypothesis of Volta, I think it not quite 

 useless to increase the body of evidence against it. 



If an iron wire rendered inactive by immersion in nitric acid 

 is associated with a platina wire, and two of their ends put 

 into a solution of blue vitriol, not the siiiallest quantity of 

 copper will be precipitated on the platina ; but if the inactive 

 iron is thrown into chemical action by being touched within 

 the solution, either with a common iron wire or by any other 

 metal which chemically acts upon the copper salt, at the very 

 moment of contact a film of copper makes its appearance on 

 the platina. Now if, according to the views of Volta, electri- 

 city be excited by the mere contact of different metals, in the 

 case in question a current should be produced, and in con- 

 sequence of such a current chemical decomposition should 

 take place, that is to say, copper should be eliminated at the 

 platina. But from such not being the case, it follows that 

 there is no current, consequently no electricity, produced by 

 the contact of iron and platina. By having recourse to the 

 galvanometer, the absence of a current under the circumstances 

 mentioned is placed bej^ond doubt. If the inactive iron wire 

 is connected with one end of the wire of the galvanometer, the 

 platina wire with the other one, and if the two free ends of 

 the iron and platina wires are plunged into a solution of 

 blue vitriol, not the least deflection of the magnetic needle 

 takes place; but as soon as the part of the inactive iron wire 

 immersed in the solution is touched with a metal capa- 

 ble of causing chemical action, the needle becomes agitated, 

 and at the same time a deposition of copper takes place on 

 both wires. From this fact it appears that the oxidation of 

 iron has no sooner been occasioned than two effects of a 

 current are produced ; chemical decomposition of an electro- 

 lyte, and affection of the needle. Now as previously to oxida- 

 tion no such effects are obtained, we are fully entitled to draw 

 the inference, that the phaenomenon of oxidation bears to 



* See Mr. Faraday*s conclusive proof, also drawn from the relation of 

 iron ami platina, Lend, and Edinb. Phil. Mag., July 1836, p. 60.— Edit. 



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