42 M. Bequerel on the Electro-motive Actions [July, 



Article VIII. 



Abstract of M. BequereVs Paper on the Electro-motive Actions 

 produced by the Contact of Metals with Liquids, and on a Pro- 

 cess for ascertaining, by Means of the Electro-magnetic Effects, 

 the Change which certain Solutions undergo by Contact with 

 the Air. (Read before the Royal Academy of Sciences, 

 April, 1824.)* 



In former papers presented to the Society, M. Bequerel had 

 attributed the electrical effects observed during chemical action, 

 solely to the play of affinities exerted between the combining 

 bodies ; concluding that during such action the alkali takes 

 positive, and the acid negative electricity, and neglecting to 

 take into the account the effect resulting from the contact of the 

 acid with the platina cup which contained it, and that of the 

 alkali on the jaws of the forceps (which were also of platina) in 

 which it was held, an action, however, which must by no means 

 be overlooked. 



The apparatus which M. Bequerel employed in his present 

 experiments is similar to the electroscope invented and described 

 by M. Bohnenberger, in the Bibliotheque Universelle, Nov. 

 1820 (see also Annates de Chimie, 1821, vol. xvi.), but instead 

 of two dry piles placed vertically, he uses only one placed in a 

 horizontal position, on a wooden support ; to each pole a metal- 

 lic plate, about three inches long, is fixed vertically, between 

 which the gold leaf is suspended, in contact with the lower 

 plate of the condenser ; the condensing plates being nine inches 

 in diameter. The delicacy of this instrument is such that it is 

 sensible to the action of an excited glass tube at the distance of 

 eight or ten feet. 



A brass capsule, containing an alkaline solution, was placed 

 on the upper plate of the condenser, and a communication esta- 

 blished between it and the ground by touching it with the finger, 

 or a moistened slip of gold-beater's skin, the lower disc being 

 also in connexion with the ground ; in a few seconds after, the 

 upper plate was removed, and the gold leaf flew to the positive 

 pole ; consequently the alkaline solution had become positive 

 from contact with the copper, and the metal negative. 



When sulphuric acid was substituted for the alkaline solution, 

 the electricities were reversed. 



To ascertain the electro-motive action of different metals by 

 contact with acid and alkaline solutions, a capsule of the metal 

 containing the solution was placed on the upper plate of the 

 condenser ; the lower plate was then touched with a slip of the 



* From the Annalcs de Chimie. 



