Composition Dependence of the Thermal Diffusion Factor of Binary Gas Systems

The thermal diffusion factor, αT, is measured as a function of composition for binary systems Ne–Ar, Ne–Xe, H2–He, H2–Xe, H2–O2, and H2–N2 in a glass two-bulb apparatus at an average temperature of about 318.6°K. The gas samples from the two bulbs are analyzed on a differential thermal conductivity analyzer within an accuracy of about ± 0.025%. The estimated uncertainty of our αT values is about ± 2%, and these are compared with the existing αT values as reported by other workers and with the predictions of Chapman–Enskog kinetic theory and modified Buckingham exp-6 potential. This simple theory is not able to explain the results on systems involving polyatomic gases, and a theory which should consider the details of inelastic collisions is necessary for reliable interpretation of such systems.