of Electrical and Chemical Changes. 191 



agents which, in proportion to their surface and their num- 

 ber, occasioned the constant circulation of a certain quantity 

 of electricity through the fluids, or the connecting wires in 

 the pile ; and the chemical changes occurring in these fluids 

 were considered as mere results, and not necessarily con- 

 nected with the circulation. The inactivity of combinations 

 where no chemical changes occur, is sufficiently hostile to this 

 view ; but an examination of some of the circumstances of the 

 construction of compound electrical combinations, will bring 

 this hypothesis, and that which I have ventured to adopt, 

 more distinctly into comparison. 



Let a piece of zinc and a piece of platinum, both in glasses 

 filled with a solution of nitrate of potassa, be connected through 

 the multiplier, and let the glasses be joined by asbestus mois- 

 tened with the same fluid ; the needle will mark electrical ac- 

 tion : let the two glasses now be joined by an arc composed 

 of zinc and platinum, in such a manner that the order is Vol- 

 taic, i. e. that the zinc is opposite to the platinum, in the ori- 

 ginal combination — the effect will be increased. Now let an 

 arc of pure zinc be introduced ; the effect will be less than 

 with the double arc, but superior to that with the asbestus, 

 and the pole of the zinc opposite the platinum will oxidate, 

 and that opposite the zinc will give off" hydrogen. Let arcs of 

 other metals be substituted for the zinc ; for instance, of tin, 

 of iron, of copper, of silver, of tellurium : the electrical effects 

 will diminish with the oxidability of the metal ; and with tel- 

 lurium, which does not oxidate at the positive pole of a vol- 

 ta,ic battery, they will be destroyed ; and the case is the same 

 with rhodium, palladium, and platinum. That the effect does 

 not depend upon any circumstance connected with conducting 

 power is evident; for charcoal, which is a very imperfect con- 

 ductor, acts like an oxidable metal ; and a very fine wire of 

 platinum, terminated by a small piece of oxidable metal, acts 

 more efficiently when the oxidable metal is opposite the nega- 

 tive pole, than if the whole chain had been composed of ox- 

 idable metal ; but entirely destroys the effect when the oxida- 

 ble metal is opposite the positive pole. 



If the contact of the metals only was necessary for conti- 

 ■ nued electro-motion, these results, in which a simple homo- 

 geneous chain is interposed between the fluids, would be im- 

 possible ; but they are a necessary consequence of the electro- 

 chemical theory, in which the destruction of the positive sur- 

 face by the chemical negative agent is regarded as a necessary 

 condition ; and platinum and tellurium acted like zinc, when 

 their surfaces opposite to the platinum were plunged into di- 

 luted nilro-muriatic acid. 



If 



