Contact action electrification

Electrification arises by contact of metal plates more readily in a dry atmosphere than in a moist one, although in the first there is no apparent chemical action and a pronounced one in the second. In the cell dilute nitric acid, zinc, and copper, the side of the zinc exposed to the acid is positive, but in the cell zinc, water, and dilute nitric acid, the surface exposed to the acid is negative, although the chemical action is the same in both cases. 

Becquerel concluded that the current was produced by the chemical action of the acid on the alkali, and Faraday (XVII, 2074) said he had believed, with Davy (see p. 72), that acids and alkalies did not in combining evolve electricity in large quantity when they were not parts of the electrolyte, but now BecquereFs pile is a perfect proof that when acid and alkali combine an electric current is produced. BecquereF was cautious and thought both contact and chemical action were involved. He first adopted Davy s theory that electrification arises by contact but the current is maintained by chemical action, but later modified this view somewhat. His electrochemical theory was similar to Ampere s (see p. 176). 

August Arthur De la Rive (Geneva, 9 October i8oi Marseilles, 27 November 1873), F.R.S., professor of physics in the Academy of Geneva, was after Parrot one of the first to oppose the contact theory and maintain that chemical action was the sole origin of the electrification on the contact of metals and in cells. Faraday praised De la Rive (who was a personal friend) as most clear and constant in his views (XVI, 1797). De la Rive s theory of electrolysis has been mentioned (p. 28). Besides his very numerous papers, he wrote an excellent textbook and edited an Archives de V lectricite (5 vols., 1841-5), which was a collection of current work on the subject. ... 

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