CONNECTIONS BETWEEN VARIOUS FORMS OF SECOND LAW OF THERMODYNAMICS

The forms of the second law due to Carathéodory, Kelvin and Clausius are examined. The possible forms of thermodynamics which may be deduced from each of these statements are found before the connections between the separate forms of the law itself are examined. It is found that the usual proof of the equivalence of the Kelvin and Clausius statements is invalidated at negative absolute temperatures. However, it is shown that the Clausius statement is equivalent to the modified form of the Kelvin principle which is applicable for both positive and negative absolute temperatures. © 1969 Società Italiana di Fisica.