Ternary mutual diffusion coefficients of sodium chloride-strontium chloride-water at 25.degree.C. 1. Total concentrations of 0.5 and 1.0 mol.cntdot.dm-3

Abstract

Mutual diffusion coefficients have been measured for aqueous NaCl-SrCl/sub 2/ mixtures at 25/sup 0/C by using free-diffusion Rayleigh interferometry. These diffusion experiments were done at total molarities of 0.5 and 1.0 mol x dm/sup -3/ and with molarity fractions of 1/3, 1/2, and 2/3. Main-term diffusion coefficients for NaCl and SrCl/sub 2/ show a 10-15% variation with concentration and composition. Coupled diffusion is important for these systems, with cross-term diffusion coefficients being 6.5-36% as large as their corresponding main terms. At a constant molarity ratio, doubling the concentration causes cross-term diffusion coefficients to increase. Attempts to estimate the ternary solution diffusion coefficients from those of their corresponding binary solutions or from the ternary solution analogues of the Nernst-Hartley equation do not yield particularly accurate results.