The thermodynamics of mixtures as a model case of rational thermodynamics

Developments of the theory of diffusion conceived by Fick (1855) in analogy to Fourier's relations of heat conduction are examined along with advances regarding the theory of mixtures made by Stefan (1871), Lohr (1916), and Eckart (1939). It is pointed out that a weakness of the considered theoretical developments is related to the paradox of diffusion theory in connection with the implied infinite propagation velocity of a concentration perturbation. A description is presented of a new formulation of the thermodynamics of mixtures which provides a solution for the paradox of heat conduction theory. The new formulation is based on rational thermodynamics. Attention is given to the field equations of the new theory of the thermodynamics of mixtures, the principle of material objectivity, and the entropy principle.