Thermal Diffusion in the Critical Region of Binary Liquid Systems

Abstract

We discuss diffusion (including sedimentation) and thermal diffusion in the critical region (both for liquid‐liquid and vapour‐liquid equilibria) of binary fluid systems. In particular, we present diagrams and discussions of experimental values of diffusion coefficients, sedimentation coefficients, and thermal diffusion factors for the liquid systems n‐hexane + nitrobenzene (with upper consolute point) and water + triethylamine (with lower consolute point), both at 1 bar, and for the fluid system methane + propane at about 73°C in the critical vaporization region. In the last case, we check a formula proposed by the author in 1950.

Prediction of binary diffusion coefficients in non-ideal mixtures from NMR data: Hexane–nitrobenzene near its consolute point

“…Predicted values are compared to measured binary diffusion coefficients reported by several authors over a range of temperatures and compositions near the consolute point (Claesson and Sundelof, 1957;Siry, 1966;Haase and Siry, 1968;Haase, 1972;Wu et al, 1988). Hamann et al (1972) demonstrated, using spin-echo NMR, that there is no anomaly in the tracer diffusion coefficients of components in a mixture near its consolute point, arguing that this is as expected because the anomaly in the mutual diffusion coefficient is contained within the thermodynamic correction factor.…”

Theoretical model of thermal diffusion factors in multicomponent mixtures

“…Firoozabadi model Shukla and Firoozabadi, 1998 has been applied for the prediction of binary thermal diffusion factors Ž of several mixtures consisting of hydrocarbon species C rC , . Ž C rC , C rC , C rC , nonhydrocarbon species ArrCO , Haase et al 1994 . The model was also found to offer a significant improvement over the earlier Ž .…”

Molecular, pressure, and thermal diffusion in nonideal multicomponent mixtures

“…The behavior of the thermal diffusion coefficient for binary mixtures in the critical region has been the subject of several Ž studies in the three last decades Hohenberg and Halperin, 1977;Sengers and Levelt Sengers, 1986;Anisimov and Kiselev, 1992;Kiselev and Kulikov, 1994;Sengers, 1994, 1996;Anisimov et al, 1995;Kiselev, 1997;Cheng et al, 1997;Sakonidou et al, 1998;Kiselev and Huber, 1998;Giterman and Gorodetskii, 1970;Mistura, 1972Mistura, , . 1975Haase et al, 1994Haase et al, , 1971Rutherford and Roof, 1959 . It has been shown using the mode᎐mode coupling analysis Ž . Mistura, 1972Mistura, , 1975 that thermal diffusion coefficients of a binary mixture have a finite value at the critical point.…”