On electroosmosis and related phenomena

Abstract

We describe the transport processes occurring in a conducting liquid system with a diaphragm separating two subsystems of equal temperature and composition, but with different values of pressure and electric potential, in terms of measurable quantities. We show how these quantities are correlated to the (partly non-measurable) phenomenological coefficients of the conventional linear relations of non-equilibrium thermodynamics. We establish some general equations and inequalities relating to the permeation coefficients, the electric conductance, the electroosmotic coefficient and the streaming conductance. We also derive the laws governing the evolution in time of our system for both potentiostatic and galvanostatic conditions and thus complete the description of the irreversible processes possible in the system at hand. We finally present results of recent measurements on aqueous potassium chloride solutions (for molalities between 10 −4 mol/kg and 10 −1 mol/kg and for temperatures between 15°C and 35°C) with silver—silver chloride electrodes and a glass filter disk. We carry through a check of Onsager's reciprocity relation and of an inequality fixing an upper limit for the absolute value of the electroosmotic coefficient.