Theory of electrochemical action

English chemist Sir Humphry Davy, who developed the first coherent theory of electrochemical action. 

Faraday seems to have been reluctant to emphasise this quantitative relationship. For him this was not yet a law of nature, for laws were special, not to be lightly enunciated, and in the case of quantitative laws difficult to establish by experiment because there might always be exceptions. All his earlier discoveries -electro-magnetic rotations, induction and the dynamo etc - had been qualitative effects where it was possible to demonstrate these phenomena and thus make them accessible to an audience in such a way that they would accept the visible experimental reasoning. He had departed from this with the identity of electricities, as he had had to resort in many cases to using the experiments of others to establish this result. In his electro-chemical work Faraday had to make more departures from what had been his normal practice. He had proposed a quantitative relationship, a new theory of electrochemical action and a theory of matter to support this - things which Faraday had never done before as a mature scientist. As I... 

Figure 3. Faraday s illustration of his theory of electrochemical action. From Phil.Trans.. 1833, 123. plate 19.

It was then natural to assume further that the usual operation of elective affinity is itself electrostatic, the attraction of oppositely charged atoms of different species. Davy in England, and Jons Berzelius in Sweden, both soon came to this view, and the latter formulated an electrochemical theory of the formation of compounds, published in 1814, which put forward this dualistic hypothesis in explanation of all chemical action. Berzelius even extended these ideas into organic chemistry, proposing that groups of atoms can form compound radicals , positive and negative, which then join together as elements would. 

Krichmar SI (1965) On the theory of the levelling action in the electrochemical behaviom of metals. Elektrokhimiya 1 858-861 (in Russian) Krichmar SI (1965) Levelling mechanism in the cathodic deposition of nickel. Zh Fiz Khim 39 602-603 (in Russian)... 

Electrochemistry is a background field for a modem theory of ET based on quantum mechanics. A short summary will be given here. Electrochemical systems are heterogeneous systems where the action takes place at the interface of a solid metal or semiconductor called the electrode, and a fluid, ionic conductor called the electrolyte. Electrochemistry started with Galvani, who serendipitously discovered that muscles of an animal may still move shortly after the animal has died, if its muscles come into contact with two different metals at the same time. Later, it was understood that electricity was involved and caused by the two metals rather than by the dead animal. In the year 1800, Volta constructed a pile where the voltage depended on the number of cells and therefore could become high if many cells were piled on top of each other with electrolytes, sucked up in an absorbing material, in between. 

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). 

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