ONSAGERS'S RECIPROCAL RELATIONS AND THERMODYNAMICS OF IRREVERSIBLE PROCESSES

A critical assessment is presented of ONSAGER's original derivation of reciprocal relations. These relations hold if the irreversible fluxes (time derivatives of state variables) are linear functions of the driving forces, but the latter may themselves be nonlinear functions of the state variables. This is an example amongst others of nonlinear behaviour that falls within the framework of (quasi) linear thermodynamics of irreversible processes. The discussion includes the variation principle of the least dbsipation of energy.