RIGOROUS OPERATIONAL DEFINITION OF ENTROPY NOT BASED ON THE CONCEPTS OF HEAT AND OF EMPIRICAL TEMPERATURE

A rigorous and general logical scheme for the definition of entropy is presented, which is based on a complete set of operational basic definitions and is free of the unnecessary assumptions that restrict the definition of entropy to the stable equilibrium states of simple systems. The treatment applies also to systems with movable internal walls and/or semipermeable walls, and with chemical reactions and and/or external force fields. Preliminary and auxiliary to the definition of entropy are the definition of thermal reservoir and an important theorem which supports the operational definition of temperature of a thermal reservoir. Whereas the thermal reservoir must be a normal system, the definition of entropy applies, in principle, even to special systems, i.e., system with both a lower and an upper bound in energy.