Thermodynamics of the lanthanide trifluorides. II. The heat capacity of praseodymium trifluoride PrF3 from 5 to 350 °K

The heat capacity of PrF3 was measured by aneroid adiabatic calorimetry from 5 to 350 °K. The following results were obtained for PrF3 (c) at 298.15 °K: the heat capacity Cp°= (92.65 ±0.09) J °K−1 mole−1, the entropy S°= (121.22±0.12) J °K−1 mole−1, the enthalpy (HT°−H0°)= (17 946±18) J mole−1 and the Planck function −(GT° −H0°)/T=(61.02±0.06) J °K−1 mole−1. Recommended thermal functions from 400 to the melting temperature, 1672 °K, are presented in tabular form. The excess heat capacity due to the internal electronic energy levels of Pr3+ in PrF3 is calculated from spectroscopic data and compared with excess heat capacity derived from calorimetric results.