228 On the Voltaie Relations of certain Pei'oxides^ ^c, 



tion. I will try to render this idea of mine somewhat clearer by 

 applying it to some particular cases. Supposing a voltaic circle 

 to be composed of platina, peroxide of lead, and nitric acid ; 

 I say that the current excited in such an arrangement is due, 

 first, to the tendency of the acid to unite with the protoxide of 

 lead, or, what is the same, to the tendency of one proportion 

 of the oxygen to separate from the peroxide ; secondly, to the 

 tendency of water to combine with the same protoxide to form 

 a hydrate ; and thirdly, to the tendency of water to withdraw a 

 proportion of oxygen from the peroxide to produce peroxide 

 of hydrogen, which tendency, from very well-known chemical 

 reasons, is yet increased by the presence of the acid. It is true 

 that none of the said tendencies do lead to any chemical re- 

 sult, for no nitrate of lead, no hydrate, no peroxide of hy- 

 drogen is actually produced ; but are we allowed to infer, from 

 the want of a practical result, that no chemical action what- 

 ever takes place when nitric acid and peroxide of lead are put 

 in contact with one another ? I ask, are we to suppose that 

 the chemical affinities alluded to are entirely dormant, and in- 

 capable of any exertion ? The results from my late experi- 

 ments induce me to answer the question in the negative. 

 Being quite of your opinion, that chemical affinity and cur- 

 rent electricity are but different forms of the same thing, I 

 cannot help thinking that any sort of chemical action or ten- 

 dency must be capable of being transformed into the shape of 

 a current. For that current which is produced by inactive 

 iron (being voltaically associated with platina) I likewise ac- 

 count by a chemical tendency on the part of the former metal. 

 Though inactive iron be not in the least attacked by nitric 

 acid, its affinity for the oxygen of the latter is, on that ac- 

 count, by no means entirely destroyed ; the metal whilst sur- 

 rounded by the acid is continually tending to oxidize itself, 

 and the current excited in such a case is nothing else but as 

 it were the electrical translation of a chemical exertion. 



All the cases above stated, where currents are observed 

 independently of any chemical change, can easily be explained 

 by applying to them the same principle as that by means of 

 which we have accounted for the current produced by nitric 

 acid and peroxide of lead, &c. Having already passed the 

 usual limits of a letter, I add only one more observation to 

 my former, and I have done. 



According to my experiments peroxide of silver proves to 

 be the most powerful means for exciting in iron its peculiar 

 voltaic condition. It surpasses in this respect even the per- 

 oxide of lead. An iron wire, for instance, one end of which 

 is covered with only a small particle of the first-mentioned 



