Determination of thermal diffusion coefficient in equimolar n-alkane mixtures: Empirical correlations.

In this article we determined the thermal diffusion coefficient (D(T)) in equimolar mixtures of n-alkanes nC(i)-nC(12) (i=5,6,7,8,9,17,18), nC(i)-nC(10) (i=5,6,7,15,16,17,18), and nC(i)-nC(6) (i=10,12,14,16,18) at 25 degrees C and at atmospheric pressure using the thermogravitational technique. The results obtained from this study together with the previously published ones in the series of nC(i)-nC(18) (i=5,6,7,8,9,10,11,12,13) show that the main parameter that determines D(T) in each series is in association with the molecular weights of the mixture's components. However, an empirical quantitative correlation has been obtained between D(T), the molecular weights of the components, the viscosity, and the thermal expansion coefficient of the mixtures. This is the first report of a closely accurate correlation for D(T) in liquid mixtures.