with oxidation 

 in a metal 



72 0N THE THEORY OF GALVANISM. 



formly found the furface of the zinc covered with a white 

 cruft ; in this cafe the water employed in diflblving the potafh, 

 oxidates the zinc in confequence of the attraction which fub- 

 fifts between the oxide of zinc and the fixed alkali. We con- 

 clude it to be a general fad, that whenever a metal is oxi- 

 Probably the dif- dated the electric fluid is difengaged, and it is probable that 



deaSri ™U°«i- the reverfe of this P ro P ofition will be found to be true, viz. 



ways attended that whenever electricity is difengaged from a metal it becomes 

 oxidated. It will appear therefore, that the experiments 

 which were made with fo much accuracy by Sig. Volta, upon 

 the different electricities produced in metals by mutual con- 

 tact, though certainly inadequate to form a complete theory 

 of the action of the pile, are yet not to be difregarded in our 



The true theory attempts to increafe the power of the apparatus. In order that 



fuppofed to be ; ts CO nitruction be adapted for exhibiting the greateft energy, 

 that of Volta . ... . ^ , V , , , , , , r i 



combined with jt will be neceflary both that the metals employed be luch as 



to produce a current of electricity when brought into contact, 

 and alfo that the interpofed fluid fhould rapidly oxidate one of 

 the metals without exercifing any action upon the other. The 

 combination of zinc and filver anfwers the firfl of thefe con- 

 ditions, and accordingly affords the belt materials for the for- 

 mation of the pile. With refpect to the interpofed folution, 

 the muriates, and particularly the muriate of ammoniac, have 

 for the moft part been found the mod efficacious, probably in 

 confequence of the attraction which fubfifts between zinc and 

 the muriatic acid. The muriat* ."ammoniac is known how- 

 ever to act readily upon copper as well as upon zinc, and yet 

 we find that this fait in a ftate of folution powerfully excites 

 the energy of a pile compofed of zinc and copper, a fact which 

 feems to militate againft our hypothecs. With a view to il- 

 Juftrate this point the following experiments were performed : 

 per. f. Zinc 1ft. A piece of zinc was expofed to the action of a faturated 

 expofed to fatu- folution of the muriate of ammoniac, a fmall quantity of hi- 



that of oxida- 



tion 



muriate "ofTnv d ro g en gas was difengaged, the fluid acquired an excefs of 

 moma caufed alkali, and after fome time the metal became covered with a 

 emiflion of hi- 

 drogen, abforbed 

 fome acid, and 

 became white. 



white cruft. 2. A clean plate of copper was placed horizon- 

 tally in a folution of the muriate of ammoniac; after a few 

 hours the upper furface of the metal was covered with a bright 

 in like circum- green cruft, while the under furface became beautifully flud- 

 ftanceswasox- jgj w ft n f ra all, tranfparent, and nearly colourlefs cryftals. 

 forbedacid,"&e. Thefe cry Hals after expofure to the air aflumed a green hue, 



fimilar 



