The heat capacity and thermodynamic functions of celestine SrSO4

The heat capacity of natural strontium sulfate - mineral celestine - has been measured over the range of 5-320 K by the method of adiabatic calorimetry and its thermodynamic functions have been determined. The methods of X-ray phase analysis, Raman spectroscopy and electron probe microanalysis have confirmed the adequacy of the sample to mineral celestine. The standard values of thermodynamic functions were: C°p(298.15) = 100.30 ± 0.11 J mol−1 K−1, S°298.15 = 123.44 ± 0.28 J mol−1 K−1 and ΔH°298.15 = 18, 406 ± 33 J mol−1. The heat capacity and thermodynamic functions of celestine have also been calculated by means of methods of semi-empirical quantum-chemical calculation and the theory of crystal lattice dynamics.