Investigation of potassium sulphate–calcium sulphate binary system by Knudsen effusion mass spectrometry

Abstract Vaporisation studies of pure K 2 SO 4 and mixtures of K 2 SO 4 and CaSO 4 in the quasi-binary K 2 SO 4 –CaSO 4 system using Knudsen effusion mass spectrometry resulted in the determination of thermodynamic data. From the partial pressures of the gaseous species over the condensed phases it was possible to determine the sublimation enthalpyΔ sub H and the thermodynamic activities of the components. The sublimation enthalpy of K 2 SO 4 agrees very well with that of two literature sources. For the first time the experimental data of activities of K 2 SO 4 and CaSO 4 in the binary system could confirm the theoretical studies.