268 Dr. SclicEiibein's Experimental Researches on a peculiar 



inclined to infer that the affinity of iron for oxygen is de- 

 stroyed by a current moving through tlie metal in a certain 

 direction, and that the affinity lost in this way by the iron is 

 revived by an opposite current. To ascertain whether this 

 view holds good generally with regard to iron, I have made 

 a series of experiments, the results of which are as follows. 

 I introduced an iron wire which had previously been con- 

 nected with the positive pole of a small battery, into an aqueous 

 solution of the common sulphate of copper, by means of which 

 the circuit was closed. According to my hypothesis no ac- 

 tion whatever is to take place on the part of the iron upon the 

 solution, under the circumstances here stated. My expectations 

 were fully realized, for after many hours' action of the pile 

 not the smallest particle of copper was deposited on the iron 

 wire, its surface had not undergone the least change, and du- 

 ring the whole time of action oxygen was evolved at the iron. 

 But as soon as the passage of the current through this metal 

 was opposed only for a moment, for instance, by taking out 

 of the copper solution either the. negative polar wire or the 

 positive one, there appeared on the surface of the latter a film 

 of copper. (The same result was obtained by joining momen- 

 tarily the two polar wires within the solution, or by touching 

 the iron wire with another metal capable of precipitating cop- 

 per.) 



Now, by these facts I think two things are clearly shown, 

 first, that iron ceases to have any affinity for the oxygen both 

 of the oxide of copper and of the water decomposed by voltaic 

 action, and secondly, that this state of chemical indifference 

 lasts only so long as there is a current passing from the iron 

 into the copper solution. This influence of current electri- 

 city upon the chemical bearings of iron is highly interesting, 

 not only on account of its being contrary to the electro-che- 

 mical notions hitherto entertained on the subject, but also on 

 account of the circumstances under which the oxygen result- 

 ing from the decomposition of water is presented to iron. 

 These circumstances are, indeed, of such a kind as highly to 

 favour the oxidation of the metal, for oxygen in a nascent 

 state is brought into contact with iron, and there is at the same 

 time a portion of the acid of the salt set free by voltaic action 

 at the iron wire, which also tends to occasion the oxida- 

 tion of the latter. The same remarks apply to the fact al- 

 ready stated, that iron is not acted upon by nitric or any other 

 oxyacid, provided this metal is placed under the influence of 

 the pile in the manner above mentioned. Iron, however, 

 may acquire the property of being not acted upon by nitric 

 acid or solutions of certain metallic salts without being sub- 



