Salvanic Powers of different Melals, 315 



Exptritnent I.— 'Zinc, combined with gold-— filvcr — iron — copper «— lead — tin — 

 ttiercury. 



The refults of all thefe combinations were .•—the caudle fenfation felt by the tongue ; 

 the irritation and galvanic fhock ; and the oxydation of the copper wire. The zinc always 

 forming the oxydating bafe or pole, and the other metals conftituting the gafeous bafe 

 or pole. 



In the combination with gold, (which was 40 guineas, and the zinc, the dlmenfions of 

 an half crown piece) the galvanic apparatus feemed to afl with more vigour than under 

 any other combination, and which was made apparent by comparing it with an apparatus 

 compofed of {hillings inftead of the half crowns, which were employed in all the other 

 combinations in which filver was ufed. In the combination of zinc with Giver, the ap- 

 paratus, which was compofed of 40 pairs of zinc and half crowns, afted with about the 

 fame power as the gold apparatus ; but this difference might be obferved, that in the gold 

 apparatus the wire connedled with the zinc bafe or oxydating pole began, after having 

 depofited much green oxide of copper, to give out bubbles of air, when, in the filver and 

 other apparatus, the wire connected with the gafeous bafe, after a {hort time, began to 

 depoGt oxide ; that is, in the gold apparatus the power of producing gas feemed to pre- 

 dominate, and in the other combinations with zinc, that of producing oxide. 



The combinations of zinc with the other metals produced much oxide and gas, and 

 their powers of a£ling feemed to be in the order of iron, copper, lead, tin, mercury. In 

 the combination with mercury, the effefts were the moft feeble. The furface of the zinc 

 in conta£l with the mercury became, of courfe, much amalgamated. 



The green oxide of copper in the tubes was examined by putting fome drops of am- 

 moniac (aqua ammonia purtz) into each of the tubes j the green oxide was dlflblved, 

 and the water acquired a blue tinge, but fome flakes of a brown fubftance remained in the 

 tubes, not afted upon by the ammoniac. This brown matter was not always formed by 

 all combinations, but the filver and copper always produced it. 



Experiment 2. — Iron, combined with gold — filver — copper — lead — tin — mercury. 



In thefe combinations the refults were nearly fimilar to thofe of the firft experiment, 

 the iron forming the oxydating bafe or pole, and the other metals conftituting the oppofite 

 or gafeous bafe or pole ; but thefe apparatus adled more feebly, than the combinations 

 with zinc, excepting when iron was combined with mercu»y, with which it feemed to a6l as 

 powerfully as any combination in the firft experiment. With gold and filver, iron feemed 

 to aft tolerably well, produced much oxide, and gas. With copper it a£ted more feebly, 

 and very minute bubbles only of air were produced. With zinc and tin, it only formed 

 a cloud in the water, and no gas appeared at the extremity of the oppofite wire. The 

 powers of thefe combinations with iron appeared to be in the order of mercury — ^gold—r 

 filver — copper— lead — ^tin. ^ 



The different colours and quantity of ruft formed upon the furfaces of the iron piece* 

 when combined with mercury, gold, and filver, compared with what was formed in 



S s 2 the 



