Thermodynamics of solids with a state equation

The thermodynamic relations describing equilibrium of a multi-phase thermoelastic solid are obtained in a way similar to that used in the multiphase fluid theory. The phase transitions of the first order are defined and equilibrium equations of the Clapeyron-Clausius type are derived. Also, the phase transitions of the the second order are introduced and equilibrium equations of the Ehrenfest type are obtained. A general theory is illustrated by examples.