IRREVERSIBLE THERMODYNAMICS

There are alternative sets of postulates which yield entirely equivalent results for several important theories. In such cases the choice of a parti-cular set of postulates may be based upon mathematical simplicity, close relationship to experiments or to the nature of the theory, or merely personal taste. While the postulate of conservation of energy is usually presented in similar form for thermodynamics or statistical mechanics, the form of the postulate comprising the second law is commonly very different. In thermodynamics the postulate may be in terms of the impossibility of an isothermal engine producing work at the expense of heat while in quantum statistical mechanics one postulates equal a priori probability for all individual quantum states. It is the purpose of the present paper to point out that there are such alternatives for the additional postulate necessary to derive the Onsager equations for the irreversible thermodynamics of processes in the linear rate law region near equilibrium. The heat engine, which was the primary subject of interest during th