THERMODYNAMICS OF THE LANTHANIDE TRIFLUORIDES .2. HEAT-CAPACITY OF PRASEODYMIUM TRIFLUORIDE PRF3 FROM 5-DEGREES-K TO 350-DEGREES-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-1mole-1, the entropy S° = (121.22±0.12) J°K-1mole-1, the enthalpy (HT°-H0°) = (17946 ± 18) Jmole-1 and the Planck function -(GT° - H0°)/T = (61.02 ± 0.06) J°K-1mole-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. © 1979 American Institute of Physics.