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

Abstract

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 C_p°= (92.65 ±0.09) J °K⁻¹ mole⁻¹, the entropy S°= (121.22±0.12) J °K⁻¹ mole⁻¹, the enthalpy (H_T°−H₀°)= (17 946±18) J mole⁻¹ and the Planck function −(G_T° −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.