General Approach to the Study of Electrical Conductance and Its Relation to Mass Transport Phenomena

A method of writing phenomenological equations for the description of electrical and mass transport, based on approaches of Onsager and of Klemm, is shown to give rise to a set of coefficients defined in a particularly useful and economical way. Conceptually akin to friction coefficients, these quantities are shown to tie together the results of such very different measurements as electrical conductance, transference numbers, and diffusion coefficients in such a way that a single type of physical concept can be applied in interpreting the results of all three. The characteristics of the phenomenological friction coefficients are examined for three different classes of electrolyte: electrolytic solutions, ionic crystals, and molten salts. Known limiting relations, such as the Nernst-Einstein relation, are shown to follow from the macroscopic treatment in cases where they are experimentally valid. In certain cases it is shown how the macroscopic treatment can be made more consistent with a microscopic model through alternative selection of the entities to be taken as components. Some macroscopic criteria are offered as bases for such selection in cases where more than one possibility seems reasonable.