Heat capacity (5 to 350 K) and recommended thermodynamic properties of barium uranate (BaUO4) to 1100 K

Abstract Adiabatic calorimetry was used to determine the low-temperature heat capacity of BaUO 4 from 5 to 350 K. No anomalous behavior was observed, the curve of heat capacity against temperature being of the normal sigmoid shape. From these measurements, the following thermodynamic properties (298.15 K) were obtained: C p o = (125.27±0.25) J K −1 mol −1 ; S o = (153.97 ± 0.31) J K −1 mol −1 ; { H o ( T ) − H o (0)} = (23291 ± 47) J mol −1 ; {G o (T) − H o (0)} T = −(75.85 ± 0.15) J K −1 mol −1 . Published high-temperature enthalpy increments merge smoothly with the present low-temperature results. An earlier result for the enthalpy of formation, ΔH f o (298.15 K), has been recalculated to be −(1997.1 ± 2.1) kJ mol −1 . Recommended thermodynamic quantities for BaUO 4 have been calculated and are listed at selected temperatures up to 1100 K.