Onsager reciprocity relations derived from Maxwell reciprocity relations

Based upon recent work by the author [H. Brenner, ``Bi-velocity hydrodynamics,'' Physica A 388 (2009) 3391-3398] devoted to the foundations of fluid mechanics and transport processes, a simple model of linear irreversible thermodynamics (LIT) is developed. On the basis of this the Onsager Reciprocal Relations (ORR) applicable to LIT are shown by purely macroscopic arguments to be a direct consequence of Maxwell's Reciprocal Relations (MRR) governing equilibrium thermodynamics. Among other things, this work answers a fundamental question raised by B. D. Coleman and C. Truesdell [``On the reciprocal relations of Onsager,'' J. Chem. Phys. 33 (1960) 28-31] regarding the need for a rational basis for choosing a compatible set of forces and fluxes for which the ORR are a priori valid.