Mutual diffusion coefficients of NiCl2–H2O at 298.15 K from Rayleigh interferometry

Abstract

Volume-fixed mutual diffusion coefficients have been measured for aqueous NiCl2 form 0.0048 to 4.3648 mol dm–3(near-saturation) to an accuracy of 0.1–0.2 % at 298.15 K. These experiments were done by free-diffusion Rayleigh interferometry. NiCl2 solutions are very dark green at high concentrations, giving rise to considerable light absorption during the interferometric measurements, and so requiring some changes in procedure and a change to a second diffusiometer. Both the experimental mutual diffusion coefficients and derived thermodynamic diffusion coefficients of aqueous NiCl2 are compared with those of other transition-metal dichlorides and alkaline-earth-metal chlorides. Among the transition-metal chlorides studied so far (MnCl2, NiCl2, ZnCl2 and CdCl2), only NiCl2 behaves as a strong electrolyte and is comparable in behaviour to the alkaline-earth-metal chlorides.