V. M. Gurevich

Revised heat capacity and thermodynamic functions of GdVO4

The heat capacity of GdVO4 has been determined by adiabatic calorimetry in the range 5–345 K. The present experimental data and earlier results have been used to evaluate the thermodynamic functions of gadolinium orthovanadate (Cp0(T), S0(T), H0(T) − H0(0), and Φ0(T)) as functions of temperature (5–350 K). Its Gibbs energy of formation is determined to be ΔfG0(GdVO4, 298.15 K) = −1684.5 ± 1.6 kJ/mol.

Heat capacity and thermodynamic functions of epsomite MgSO4 · 7 H2O at 0–303 K

Geological–geophysical data obtained by the Galileo spacecraft during its traveling around Jupiter’s satellites suggest the presence of a water layer (in terrestrial terms, marine or oceanic water) from tens (Europe) to a few hundred (Ganymede and Callisto) kilometers thick beneath an outer solid ice shell [1–2]. The oceans of Europa, Ganymede, and Callsito are supposedly high-pressure electrolytic solutions. The presence of water supports the hypotheses of the existence of primitive extraterrestrial life forms in the surface ocean. The outer shells of Jupiter’s icy satellites consist mainly of H 2 O ice contaminated with dark non-ice component (carbonaceous chondrite-type matter). The data obtained by the Galileo probe point out the presence of mixtures of salt crystal hydrates ( MgSO 4 · n H 2 O, Na 2 SO 4 · n H 2 O , and others) on the ice surface of the satellites [3].

Heat capacity and thermodynamic functions of xenotime YPO4(c) at 0–1600 K

The heat capacity of xenotime YPO4(c) was measured by adiabatic calorimetry at 4.78–348.07 K. Our experimental and literature data on H0(T)-H0(298.15 K) of Y orthophosphate were utilized to derive the Cp0(T) function of xenotime at 0–1600 K, which was then used to calculate the values of thermodynamic functions: entropy, enthalpy change, and reduced Gibbs energy. These functions assume the following values at 298.15 K: Cp0 (298.15 K) = 99.27 ± 0.02 J K−1 mol−1, S0(298.15 K) = 93.86 ± 0.08 J K−1 mol−1, H0(298.15 K) − H0(0) = 15.944 ± 0.005 kJ mol−1, Φ0(298.15 K) = 40.38 ± 0.08 J K−1 mol−1. The value of the free energy of formation ΔfG0(YPO4, 298.15 K) is −1867.9 ± 1.7 kJ mol−1.

The heat capacity and thermodynamic functions of EuPO4 over the temperature range 0-1600 K

The heat capacity of EuPO4 was measured by adiabatic calorimetry over the temperature range 9.81–298.48 K. The experimental and literature data were generalized to obtain the temperature dependence of the heat capacity of europium orthophosphate from 0 to 1600 K. This dependence was used to calculate thermodynamic functions (entropy, enthalpy, and reduced Gibbs energy). The data on the heat capacity of europium orthophosphate and diamagnetic lanthanum orthophosphate were used to estimate the noncooperative magnetic transition (Schottky anomaly) value.

Low-temperature heat capacity and thermodynamic functions of DyVO4

The heat capacity of dysprosium orthovanadate has been determined by adiabatic calorimetry in the range 6.12–343.26 K. The present and earlier data have been used to calculate the thermodynamic functions of DyVO4 in the temperature range 0–350 K. We have determined the absolute entropy and Gibbs energy of formation of dysprosium orthovanadate: S0(298.15 K) = 148.34 ± 0.11 J/(mol K), ΔfG0(298.15 K) = −1671.6 ± 2.1 kJ/mol. An anomaly has been detected at temperatures below 42 K, due to the Jahn-Teller phase transformation (TC = 14.42 K). We have determined the thermodynamic characteristics of the transformations in the temperature range 0–42.63 K.

Heat capacity and thermodynamic functions of YbPO4 from 0 to 1800 K

The thermodynamic functions of YbPO4 have been determined experimentally in the temperature range 6–1745 K. The results have been used to calculate temperature-dependent heat capacity, entropy, enthalpy increment, and reduced Gibbs energy of YbPO4 in the range 6–1800 K. The Gibbs energy of formation of ytterbium orthophosphate (ΔfG0(298.15 K)) has been determined.

High-temperature thermodynamic properties of LuPO4

The high-temperature enthalpy of lutetium orthophosphate has been determined as a function of temperature in the range 432.92–1744.58 K using drop calorimetry. The present and earlier experimental data have been used to calculate temperature-dependent heat capacity of LuPO4 in the range 1–1750 K.

Heat capacity and thermodynamic properties of GdPO4 in the temperature range 0–1600 K

The heat capacity of gadolinium orthophosphate (GdPO4) measured in the temperature range 11.15–344.11 K by adiabatic calorimetry and available literature data were used to calculate its thermodynamic functions at 0–1600 K. At 298.15 K, these functions are as follows: Cp0(298.15 K) = 101.85 ± 0.05 J K−1 mol−1, S0(298.15 K) = 123.82 ± 0.18 J K−1 mol−1, H0(298.15 K)–H0(0) = 17.250 ± 0.012 kJ mol−1, and Φ0(298.15 K) = 65.97 ± 0.18 J K−1 mol−1 The calculated Gibbs free energy of formation from the elements of GdPO4 is ΔfG0 (298.15 K) = −1844.3 ± 4.7 kJ mol−1.

Heat capacity and thermodynamic functions of pretulite ScPO4(c) at 0–1600 K

The heat capacity of synthetic pretulite ScPO4(c) was measured by adiabatic calorimetry within a temperature range of 12.13–345.31 K, and the temperature dependence of the pretulite heat capacity at 0–1600 K was derived from experimental and literature data on H0(T)-H0(298.15 K) for Sc orthophosphate. This dependence was used to calculate the values of the following thermodynamic functions: entropy, enthalpy change, and reduced Gibbs energy. They have the following values at 298.15 K: Cp0 (298.15 K) = 97.45 ± 0.06 J K−1 mol−1, S0(298.15 K) = 84.82 ± 0.18 J K−1 mol−1, H0(298.15 K)-H0(0) = 14.934 ± 0.016 kJ mol−1, and Φ0(298.15 K) = 34.73 ± 0.19 J K−1mol−1. The enthalpy of formation ΔfH0(ScPO4, 298.15 K) = − 1893.6 ± 8.4 kJ mol−1.

Low-temperature heat capacity and thermodynamic functions of AlH3 and AlD3

The thermodynamic properties of AlH3 and AlD3 were evaluated from low-temperature heat capacity measurements. For α-AlH3 , C0p(298.15 K) = 41.14 ± 0.13 J/(mol K), S0(298.15 K) = 30.62 ± 0.14 J/(mol K), H0(298.15 K) – H0(0) = 5527 ± 15 J/mol, and Φ0(298.15 K) = 12.08 ± 0.06 J/(mol K). For α-AlD3 , C0p(298.15 K) = 50.82 ± 0.04 J/(mol K), S0(298.15 K) = 36.74 ± 0.12 J/(mol K), H0(298.15 K) – H0(0) = 6801 ± 10 J/mol, and Φ0(298.15 K) = 13.93 ± 0.04 J/(mol K).