394 Experiments and Obfervations on the Galvanic Phenomena. 



II. 



^n Account of fome Additional Experiments and Obfervations on the Galvanic Phenomena. 

 By Mr. Davy, Super intendant of the Pneumatic Injbtution. Communicated by the 

 Author. 



Additional Esperiments on the Caufes of the Galvanic Phenomena. 



1. OULPHURIC acid, when highly concentrated, Is poflefled of but little power of 

 a£tion upon zinc, though when diluted it diflblves it with the greateft rapidity. AiTuming 

 then the truth of the principles advanced in my laft paper, namely, that the powers of the 

 pile of Volta are primarily excited by the oxidation of the zinc, it follows, that diluted 

 fulphuric acid, when made the medium of conne<SHon between the pairs of plates, ought to 

 produce much greater effe£ls than concentrated fulphuric acid. 



This I have found is aftually the cafe. When the cells of a ferics of twenty pairs of 

 plates of filver and zinc, conftru£ted with waxen cement, in the mode defcribed in 8 of 

 my laft paper, were filled with fulphuric acid, nearly of fpecific gravity !.<),- no galvanic 

 aSion, except the produftion of a flight cauftic tafte, was perqeptible by the ufual methods 

 of trial ; though when diluted fulphuric acid was ufed the ends of the feries gave fhocks to 

 the moiftened fingers, and wires conne£led with them effe(9:ed the ufual changes in ■ 

 water. 



That concentrated fulphuric acid is not of that order of more perfefl galvanic con- 

 du£lors which, when interpofed between the plates, deftroy their deftrical effefls, is 

 evident from the following experiment : the cells of ten pairs of plates of copper and zinc> 

 conftrudted with waxen cement, were filled .with concentrated fulphuric acid ; but not the 

 flighteft galvanic power was produced. A fmall drop of water was then poured upon the 

 acid in each of the cells. The aftion of the feries was immediately fliewn by its producing 

 the ufual appearances on wires in water. 



2. The galvanic condufling powers of liquid fulphurets arc at leaft equal to thofe of 

 ■water. I found that when the fingers were plunged into glafles, containing folurion of 

 fulphuretof ftrontian conne£l:ed with the ends of a pile, the fhock was full as fenfible as i£ 

 the communication had been made through water. When the galvanic current was made 

 to aft on folution of fulphuret of ftrontian by means of filver wires, the zinc wire became 

 blackened, and gas was given out round the filver wire. But folutions of fulphurets are 

 incapable of giving oxygen to zinc ; they, confequently, ought to produce no galvanic 

 effeds when made the media of connexion of the double plates in the pile of Volta. 

 Twenty-five pairs of filver and 2inc» erefted with cloths moiftened in folution of ful- 

 phuret 



