An elementary theory of thermal diffusion

Abstract

Although a rigorous theory of thermal diffusion has been developed by Chapman and Enskog, it is desirable to have an approximate but elementary theory which reveals the physical mechanism of the phenomenon. This is given in the present paper by the application of a method similar to that used by Meyer for the treatment of ordinary diffusion in gases. It leads to an approximate formula for the thermal diffusion ratio, a discussion of which shows that it accounts for many of the characteristic properties of thermal diffusion.