E. Zanchini et A. Barletta, FINITE-MASS HEAT RESERVOIRS AND THE 2ND LAW, Nuovo cimento della Societa italiana di fisica. B, Relativity, classical and statistical physics, 110(10), 1995, pp. 1245-1258
It is proved that a simple system composed of a pure substance, at its
triple point, can exchange energy while passing through stable-equili
brium states at constant volume and temperature, and, therefore, repre
sents a heat reservoir with finite mass. Moreover, it is proved that t
he behaviour of a pair of identical simple systems composed of the sam
e substance, each in a state of the triple point, requires a slight mo
dification of some recent statements of the second law of thermodynami
cs.