Liquid mutual diffusivities of the H2O/D2O system

The liquid-phase mutual diffusivities of the water (H₂O) and deuterium oxide (D₂O) system at 298.2 K were measured using an instrument based on the Taylor dispersion technique. The instrument has been designed to match, as closely as possible, the mathematical model of ideal Taylor dispersion, minimizing all the departures from the ideal model. The diffusivities were measured over the entire concentration range and the results follow a linear dependence on molar fraction given by 10⁹D₁₂ =, where D₁₂ is in m²·s^–1. Comparison with highly accurate data obtained by a Rayleigh interferometer seems to indicate that the accuracy of the present instrument is 1%. The hard-sphere model was applied to the estimation of the mutual diffusivities of this system and good agreement was found with experiment, deviations being ±3.5%.Paper presented at the Ninth Symposium on Thermophysical Properties, June 24–27, 1985, Boulder, Colorado, U.S.A.