Charge densities and surface conductances at solid-solution interfaces

Abstract

Surface charge densities for the minerals quartz (SiO₂), corundum (Al₂O₃), rutile (TiO₂), cassiterite (SnO₂), and haematite (Fe₂O₃) have been calculated using an equation based on the kinetic theory of the diffuse layer, and requiring a knowledge of ζ-potentials. 111 addition, an equation, which avoids the difficulties of earlier expressions of the kind, has been derived enabling calculation of surface charge densities from surface conductances. Values obtained from the second equation for Fe₂O₃, SnO₂, and TiO₂ were much in excess of those calculated from ζ-potentials. The discrepancies have been attributed to considerable contribution of solid conductance to the measured surface conductance. Equations have also been derived permitting calculation of quantities characteristic of the physical properties of the porous plug packings used in the investigations.