The Dufour effect

Equations for the Dufour effect, which is the development of a temperature gradient due to diffusion, have been solved for geometrically well-defined cells which have either all walls adiabatic or adiabatic lateral walls and diathermic ends. Two self-consistent, well-ordered perturbation schemes have been used, and heat of mixing, variability of all properties, and the barycentric velocity are included explicitly. For typical nonelectrolytes, the temperature difference produced by the Dufour effect could be as large as 0.2 deg for a diffusing mixture with initial mass fraction difference of 0.8. These results can be used (1) to design experiments to test the Onsager heat-matter reciprocal relation and (2) to avoid undesired temperature variations in diffusion experiments.