The thermochemical and thermophysical properties of Cs2RuO4 and Cs2MnO4 at temperatures from 5 K to 1000 K

Abstract

Low-temperature heat capacities from 5 K to 350 K by adiabatic calorimetry and high-temperature enthalpy increments above T = 450 K to 800 K by drop calorimetry of Cs2RuO4 and Cs2MnO4 have been measured. The two compounds exhibit solid-to-solid phase transitions at T = 906.8 K and T = 1051.9 K, respectively, and melt at T = 1211.8 K and T = 1175.5 K, respectively. The enthalpies of transition and the melting temperatures have been determined by d.s.c. measurements. From the results, smoothed thermochemical and thermophysical functions have been tabulated at selected temperatures up to 1000 K. For the standard molar entropies of Cs2RuO4 and Cs2MnO4 at T = 298.15 K the values Som/R = 31.64 and 28.77, respectively, have been found.