**3. The heat capacity and thermodynamic properties of the phase transitions**

A heat capacity is a capability of the substance for absorbing some quantity of the energy that increases its temperature by 1 degree K. A measurement of the heat capacity is performed by adiabatic and isothermal methods. The first one allows attaining the most complete thermodynamic equilibrium or, in any case, the thermal balance in the calorimetric system. The adiabatic method is used for exploring the thermal processes with different times of relaxation and the metastable phases which can exist in wide temperature ranges. The heat capacities and thermodynamic properties of the phase transitions were investigated in this work by low-temperature adiabatic calorimetry (Varushchenko et al., 1997a).
