338 Experiments on the Chunk al ProduSlion and Agency of EleBrictiy, 



water, the zinc is difiblved, and yields hidrogen gas, by deconxpofition of the water : the 

 filver, not being a£led upon has no power of decotnpofing water; but, whenever the zinc 

 and filver are made to touch, or any metallic communication is made between them, 

 hidrogen gas is alfo formed at the furface of the filver. 



Any other metal befide zinc, which by aflidance of the acid employed is capable of dc- 

 compofing water, will fucceed equally, if the other wire confifts of a metal on which the 

 acid has no effect. 



Experiment 2. If zinc, iron or copper, are employed with gold in dilute nitric acid, 

 nitrous gas is formed ; in the fame manner, and under the fame circumflances, as the 

 hidrogen gas in the former experiment. 



Experiment 3. Experiments analogous to the former, and equally Gmple, may alfo be 

 made with many metallic folutions. If, for inftance, the folution contains copper, it will 

 be precipitated by a piece of iron, and appear on its furface. Upon filver merely immerfed 

 in the fame folution, no fuch efFe£t is produced ; but as foon as the two metals are brought 

 into contadt, the filver receives a coating of copper. 



In the explanation of thefe experiments, it is neceffary to advert to a point eftabliflied by 

 means of the eleftric pile. 



We know that when water is placed in a circuit of condudtors of ele£lricity, between the 

 two extremities of a pile, if the power is fufficient to oxidate one of the wires of communi- 

 cation, the wire connefted with the oppofite extremity affords hidrogen gas. 



Since the extrication of hidrogen, in this inftance, is feen to depend on eleftricity, it is 

 probable, that in other inftances, ele£tricity may be alfo requifite for its converfion into gas* 

 It would appear, therefore, that in the folution of a metal, ele£tricity is evolved during 

 the a£tion of the acid upon it ; and that the formation of hidrogen gas, even in that cafe 

 depends on a tranfitlon of electricity between the fluid and the metal. 



We fee, moreover, in the firft experiment, that the zinc, without conta£t of any other 

 metal, has the power of decompofing water; and we can have no reafon to fuppofe that the 

 conta£t of the filver produces any new power, but that it ferves merely as a conductor of 

 eleftricity, and thereby occafions the formation of hidrogen gas. 



In the third experiment alfo, the iron by itfelf has the power of precipitating copper, by 

 means, I prefume, of eledtricity evolved during its folution ; and here likewife the filver, 

 by conducing that electrity, acquires the power of precipitating the copper in its metallic 



ftate. 



The explanation here given receives additional confirmation from comparative experi- 

 ments which I have made with common ele£tricily ; for it will be feen, that the fame 

 transfer of chemical power, and the fame apparent reverfion of the ufual order of chemical 

 affinities in the precipitation of copper by filver, may be efFedled by a common eledtrical 

 machine. 



The machine with which the following experiments were condu£led, confifts of a cylin- 

 der feven inches in diameter, with a conductor on each fide, 16 inches long, and 34 inches 

 4 diameter, 



