Electro-chemistry. Part I, General theory / by R.A. Lehfeldt ... Including a chapter on the relation of chemical constitution to conductivity, by T.S. Moore.

  • Lehfeldt, R. A. (Robert Alfred), 1868-1927.
Date:
1904
Catalogue details

Licence: In copyright

Credit: Electro-chemistry. Part I, General theory / by R.A. Lehfeldt ... Including a chapter on the relation of chemical constitution to conductivity, by T.S. Moore. Source: Wellcome Collection.

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    anions in the opposite sense. An ion may move as far as one of the electrodes and there give up its charge, and appear as a deposit of ordinary matter; but, if generated far in the in- terior of the solution, will more probably collide with other molecules. When this occurs the ion may travel on again free, or its collision may break up the molecule, and so form fresh ions; or it may, by colliding with an ion of the opposite kind, recombine. The decomposition and recomposition of molecules thus continually taking place, leave at any moment a certain fraction of the ions free ; the electric force imposes— apart from their irregular heat motions—a uniform drift on all the ions that are free; and so, although no one ion need move very far, the current is conveyed by a steady procession of them towards the electrodes. It is not necessary to suppose that the electric force causes dissociation of the salt molecules; rather, since there are cases of electrolysis which will start on the application of any electric force, however small, it is more natural to assume that the dissociation is spontaneous, i.e. it is due to ordinary chemical action, and exists in a solution apart from the appli- cation of electric force at all. This leaves open the question how much of the salt is at any moment dissociated. It was at first tacitly assumed that only an infinitesimal amount existed in the ionised condition, so that the properties of the salt would, on the whole, be the same in the dissolved condition as in the solid. It was Arrhenius 1 who first put forward reasons for supposing that an electrolyte might be largely, and in some cases almost com- pletely, dissociated in solution. This view, though violently in opposition to the current chemical doctrine of the time, has continually gained support from experiment since, and may be looked upon as thoroughly established. We shall not attempt to give the arguments in its favour here, but shall adopt it as a working hypothesis, and allow the evidence in favour of it to accumulate, as the hypothesis is applied to various phenomena in turn. The theory of atomic electric charges; of the convection of 1 Zeitschr. phys. C/iem., 1. 631 (1887).