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330 by Grotthus's theory, the explanation furnishes at the same time a numerical relation between the ions which have wandered to their respective regions in the electrolyte which is not in accord with experiment.

It is an objection against Grotthus's theory, and indeed against Thomson's method given in § 282 of connecting chemical affinity and electromotive force, that, on those theories, it would require an electromotive force in the circuit greater than ^, the counter electromotive force in the electrolytic cell, to set up a current, and that the current would begin suddenly, with a finite value, after this electromotive force is reached. On the contrary, experiments show that the smallest electromotive force will set up a current in an electrolyte and even maintain one constantly, though the current strength may be extremely small.

285. The Dissociation Theory of Electrolysis.—The foundations of a more satisfactory theory of electrolysis were laid by Clausius, who proceeded from the view with which he had become familiar by his study of the kinetic theory of gases, that the molecules of all bodies are in constant motion. He assumed that the collisions of the molecules of the electrolyte occasionally caused a separation of some of the molecules into their constituent ions, and that the province of the electromotive force in the electrolyte was to direct the motion of these ions toward their respective electrodes. A considerable extension of Clausius's theory has been made by Arrhenius and developed by Ostwald and others, in which the leading idea is, that the molecules of an electrolyte in solution are always separated to a greater or less extent into their constituent ions. In many cases, and always in very dilute solutions, the separation, according to this view, is complete. This theory is called the dissociation theory of electrolysis. The ions, however, are not in the condition of the constituent parts of a molecule which have been dissociated at a high temperature (§ 219), but possess certain peculiar electrical and chemical properties. It has been proposed to call their condition in solution ionization. This term certainly possesses advantages, but