Chemical affinity depends upon the electric properties of the atoms, and their attraction is due to their electric charges. According to Davy, the cause of the charge is to be found in the contact of the atoms, since Volta believed that he had proved that when two bodies are brought into contact, they become oppositely charged with electricity. Electrolysis consists in bringing back the atoms into the condition in which they were before union. The sign of the pole at which the atoms separate defines the nature of their chaige, which is opposite to that of the pole.
Contrary^ to the prevailing view, Davy was of the opinion that electrolysis is principally a primary action, that is, the current decomposes electrolytes directly.
Berzelius's Theory difiered essentially in one point from Davy's. Berzelius assumed that the atoms do not first become electrified by touching each other, but that they are already charged before coming into contact — a c6nclusion at which Schweigger had previously arrived, without, how- ever, following it up further. The different kinds of elec- tricity concentrated at the various points of the atoms do not act outwardly with the same force, but with different strengths.
The two quantities of electricity do not require, therefore, to be unequal; for the action might be compared with that which a magnet with two equally strong poles exerts on an object placed near one of these; in this case the action of the nearer pole preponderates.
The atoms behave similarly, they also have two (electric) poles, so that the most highly charged atoms do not neces- sarily show the strongest affinity. According as the action of the positive or negative pole preponderates, the body shows positive or negative properties, that is, is attracted by the negative or positive pole of a voltaic pile.
Since in all compounds the oxygen migrates to the positive pole, oxygen was regarded as the most negative of all substances. For a similar reason potassium (and after- wards caesium) was held to be the most positive element.
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