[Theoretical reformulation and new interpretation of the law of increase of entropy]

The author alludes to the analysis proposed by Firrao (1986) as extending the scope of his own work in collaboration with H. de Rycker (1986) which distinguished between the concepts of endotropy (related to variations of internal energy of the isolated ideal gas) and exotropy (variations of expansible energy in relation to the transmission of heat). The paper achieves a theoretical bridge between the two approaches on the basis of the differential equation dS=dQ/T+dP with dP=-S/T dT, where S represents the total entropy. The first term is related directly to the variations of thermal energy, and the second (dP) represents the production of exotropy. The S-T diagram drawn in polar coordinates features a rectangular hyperbola of TS=Q/sub 0/ (constant), corresponding to positive entropy production while temperature is falling, or a straight line through the origin for S/T=C /sub 0/ (constant), the entropy varying positively or negatively as temperature rises or falls.Francai