GALVANIC ELECTRICITY. 381 



posed by the metallic plates ; and that when the 

 chemical action ceases, the disengagement of 

 electricity also ceases.* 



* From the experiments of Hitter, Davy, and others, it would 

 appear that two different metals are not requisite to the disen- 

 gagement of the galvanic fluid, but to its concentration. Sir 

 Humphrey Davy formed galvanic series of a single plate of zinc, 

 one side of which was exposed to an acid, and the other side to 

 water also by a single metal acted upon one side by an acid, 

 and on the other side by hydro-sulphurets. (Philosophical 

 Transactions for 1821.) 



It has been further shewn by M. Becquerel, that electricity is 

 evolved whenever metals are immersed in acid solutions that act 

 chemically on them. The same effect was produced during the 

 combination of acids and alkalies, when nitrate of iron acts on 

 leaves of platinum foil ; or nitro-muriatic acid upon gold ; and 

 even on mixing a concentrated acid solution with a diluted solu- 

 tion of the same acid. (Ann. de Chem. et de Phys. xxxv. 120.) 



From such experiments it has been inferred, that electricity is 

 disengaged during all chemical actions. But it is certain that 

 all chemical combinations and decompositions are attended with 

 changes of temperature that is, by the absorption or evolution 

 of caloric. The disengagement of electricity during the action 

 of the strong acids on metals, alkalies, &c. has been deduced 

 from the fact, that when the two ends of a multiplying wire are 

 made to communicate with the combining bodies, the magnetic 

 needle is deflected, as it is during the passage of a current of 

 voltaic electricity through it. But the same effect is produced 

 when one end of the multiplying wire is made to communicate 

 with melted silver, and the other end with a portion of the same 

 metal in the solid state ; or when the two extremities of the mul- 

 tiplier are made to communicate with different parts of other 

 metals when of different temperatures from which it would 

 appear that the magnetic phenomena are independent of chemi- 

 cal action, and result from the transition of caloric through the 

 multiplying wire, as will be proved further on. 



