Description of the transport of solvent and ions through membranes in terms of differential coefficients. Part 1. - Phenomenological characterization of flows

The transport of water and ions through a membrane is described by differential expressions. The system considered comprises a membrane separating two solutions of one salt with a pair of identical electrodes immersed in the solutions. Six differential coefficients characterizing the process are defined and correlated with other measurable coefficients, using Onsager's reciprocal relations in differential form. The flow of salt, the volume flow and the electric current are then described as functions of three independent variables, flows or driving forces. For each flow, the independent variables chosen are those which are most easily controlled experimentally, and the flow equations are expressed in terms of the above defined coefficients.