5. Solid/fluid and solid/solid equilibria of pure bodies

The preceding paragraphs have shown that when pressure and temperature are above the critical values, the transition between the liquid and gaseous states no longer exists. On the other hand, it is impossible to go from a solid phase to a fluid phase without discontinuity, either in the case of fusion equilibrium, between solid and liquid, or in the case of sublimation equilibrium, between solid and gas. Solid/liquid transitions are 1 ^re species transformations in which isobaric variations in enthalpy and molar entropy as a function of temperature follow the pattern shown in figure