as ejccited by Peroxide of Lead, 42f) 



not militate against the correctness of the idea, it might be 

 imagined that the connexion between the two phaenomena in 

 question depends upon the fact, that the current issuing from 

 the inactive iron carries along with it or keeps at a certain di- 

 stance from the metal, those particles of the fluid which are 

 round the metallic substance, preventing by this means imme- 

 diate contact, and consequently chemical action. This idea 

 receives some support from the fact, that an inactive iron wire 

 is to a solution of blue vitriol, as to capillary action, what a 

 solid body with a greasy surface is to water, whilst such is not 

 the case with active iron. But the single fact that this metal 

 can for any length of time remain inactive in nitric acid, under 

 circumstances which exclude the possibility of the existence 

 of a current, overthrows at once the aboVe-mentioned hypo- 

 thesis, not to mention many other facts, equally irreconcilable 

 with it. 



By the relation of iron associated with peroxide of lead to 

 nitric acid and to the solution of blue vitriol, as well as by the 

 fact that iron in this combined state excites a very strong 

 taste upon the tongue, a taste much stronger than that pro- 

 duced by any voltaic association known, I was led to suppose 

 that a powerful battery might be constructed of pairs consist- 

 ing of iron and the said peroxide. Experiments have proved 

 the correctness] of my supposition : an iron wire 0'"'5 thick, 

 3" of length, one of its ends coated with a thin film of per- 

 oxide, and each end put into a separate vessel filled with nitric 

 acid a hundred times diluted, developed a current which was 

 capable of decomposing water. For when the two vessels were 

 connected with a platina wire, hydrogen was evolved at one of 

 its ends, oxygen at the other. At the extremity of the platina 

 wire, it being placed in the vessel where the peroxide of lead 

 was, the latter gas was disengaged. Twenty-four such little 

 wires arranged into a couronne des lasses and the before-men- 

 tioned diluted nitric acid used as the exciting liquid, caused 

 a current of considerable intensity ; for it rapidly decomposed 

 water only slightly acidulated and produced likewise a sensible 

 shock. But as may easily be foreseen, such a pile is not active 

 for a great length of time ; for the hydrogen evolving at the 

 negative part of each wire, that is to say, at the end covered 

 with peroxide of lead, rapidly decomposes this substance, 

 thereby reducing the wire to its ordinary state. Any other 

 method attempted by me for the purpose of associating the 

 peroxide with iron than that mentioned in my last letter to 

 Mr. Faraday proved unsuccessful, though it is possible by 

 attaching a small quantity of peroxide to a wire in a mechani- 

 cal manner, to render this inactive in common nitric acid. 



