Electrolyte diffusion at very low concentrations in ionized water

Abstract

The diffusional behaviour of an electrolyte M_ν+ X_ν^– in water is studied up to concentrations where the effect of the ionization must be taken into account. The mutual diffusion in this system changes due to the dissociation of water under the decreasing electrolyte concentration, first to multicomponent diffusion and then, at concentrations < 10^–8 mol dm^–3, to tracer diffusions of the electrolyte ions.

By applying Nernst–Planck equations the approximate values of the proper difiusion coefficients are calculated. These rather simple calculations confirm the phenomena which were observed experimentally by Mills at low concentrations in the system H₂O + MgBr₂ at 298.15 K.