The pressure dependence of the thermal diffusion factors of the systems He–n–propane, He–octafluorocyclobutane (C4F8), and CH4–C4F8 at 300 K.

Thermal diffusion factors, αT, are reported for the systems He–nC3H8, He–C4F8, and CH4–C4F8 at 300 K as functions of concentration and pressure; excess second virial coefficients are also reported for each system. The αT values are extrapolated to zero pressure and the theory of Oost, Los, Cauwenbergh, and van Dael is used to predict the pressure dependence of αT at each concentration for comparison with the experimental results. The data for CH4–C4F8 do not agree with the theory. [ABSTRACT FROM AUTHOR]