On the Powers of diffireni Galvanic Ccmbinations. 401 



in. 



Remarks on the Powers of different Galvanic Combinations. 



1. I have found by many experiments, that when muriatic acid is introduced (In quan- 

 tities fufficicnt to produce vifible changes) into water contained in the glaffes of an efFe£livc 

 galvanic feries compofed of zinc plates and filver wires, the zinc plates are afted upon, 

 and gas is given out from every part of their furfaces ; whilfl the quantities of gas produced 

 on the filver wires are increafed only in the apparent ratio of the increafed power of the 

 feries to give the fhock. When muriatic acid is introduced into a certain number only of 

 the glaffes of a feries, fimilar changes are produced in thofe glaffes ; but there is no appa- 

 rent alteration in the nature of the phaenomena taking place in the other glaffes ; thefc 

 phaenomena are only rendered more vivid. Effe£l:s analogous in appearance take place when 

 fulphuric acid, and even when nitric acid is employed. So that it appears that the power 

 of a feries to fix oxygen upon its zinc plates, and to evolve hydrogen from its filver plates, 

 is limited, and cannot be increafed by oxydating bodies beyond a certain extent. We mult 

 confequently conclude, that only a certain quantity of galvanic influence can be made to 

 circulate through a feiies in a given time, and that the increafe of oxidation beyond a cer- 

 tain term is cpnnefted with no new increafe of power. 



2. The fubftances which are capable of rapidly oxydating the imperfe£t metals, and 0/ 

 condenfing nafcent hydrogen at the fame time, are thofe which produce the moft powerful 

 effe£ls, when made the media of connexion between the metals in the galvanic feries. The 

 nitric and oxygenated marine acids appear to be the moft powerful^of the known fluid ex- 

 citers of the pile. The folutions of metallic falts, compofed of acids and oxydes at their 

 maximum of oxidation, ftand next in order : then follow the muriatic and fulphuric acids, 

 and the neutral falts containing thofe acids, or nitric acid. 



I have lately endeavoured to make fome comparifons befween the powers of piles con- 

 {lru£ted with nitric acid, and thofe of common piles ; but without much fuccefs. The rapid 

 aftion of the acid, the evolution of gafes conne£ling the plates by moifture, and, the 

 produQlon of heat, all tended to dlfturb the refults. The fmalleft feries of plates from 

 which I was able to obtain fhocks by nitric acid, was compofed of three pairs. Six pairs, 

 with moderately ftrong nitric acid, gave a fliock more acute than that produced by a com- 

 mon pile of twenty-feven pairs, but apparently much more limited in extent ; it was felt no 

 further than the upper joints of the fingers. With twelve pairs, or ftill more numerous, 

 combinations, the (hock was always more acute and painful, than from a common pile 

 compofed of four or five times the number of plates ; but apparently more local, and felt 

 x)ver a fmaller furface. As fufion of the cement always took place when the trough wa» 

 ufed in thefe experiments, cloths wetted with the acid were generally employed ; but in no 

 cafe was it poffible to prevent the edges of the plates from being moiftened, fo that a cer- 

 tain degree of communication between the ends always exifted, and from this communi- 

 cation the effects muft have been much diminilhed. A pile with nitric acid had its power 



Vol. IV.— December 1800. 3F vcrjf 



