Ternary mutual diffusion coefficients of MgCl₂ + MgSO₄ + H₂O and Na₂SO₄ + MgSO₄ + H₂O from Taylor dispersion profiles

Abstract

The Taylor dispersion (peak-broadening) technique is used to measure the ternary mutual diffusion coefficients of the mixed salt solutions MgCl 2 + MgSO 4 + H 2 O and Na 2 SO 4 + MgSO 4 + H 2 O at 25 °C. The dispersion of the solutes is followed by differential refractometry. A simple least-squares procedure is developed to calculate the ternary diffusion coefficients from the refractive index profiles. The coefficients are measured at 0.04, 0.20, or 0.40 mol dm −3 total salt for the molar salt ratios 1:3, 1:1, or 3:1. The measured diffusion coefficients are compared with the limiting values for the completely dissociated salts. Key words: mixed salt solutions, multicomponent diffusion, Taylor dispersion, ternary diffusion coefficients.