Nernst-Hartley evaluation of the interdiffusion coefficient of aqueous nickel sulfamate using new measurements of the equivalent conductances of the ions

Abstract

A diaphragm cell for measuring diffusion coefficients consists of two well stirred solution compartments on opposite sides of a membrane, which is usually a sintered glass disk [l-4]. Once the geometric cell constant for the device has been determined by calibration, the differential diffusion coefficient of a two-component system can be determined by following the time dependence of the concentration difference (of either solute or solvent) appearing across the sinter. Recent advances in theory have placed the diaphragm cell method on a sound mathematical basis [5,6]. Subject to question, however, is the accuracy of diaphragm cell measurements of interdiffusion coefficients of strong electrolytes at high dilution [7,8]. As this is the region where the diffusion coefficient depends steeply on concentration, it is important to check the experimental values against theoretical results involving the transport coefficients. The most useful of thes,e theoretical results is the NernstHartley equation,