Products of hydrothermal treatment of selenite in potassium chloride solutions

Selenite was boiled in KCl solutions of different concentrations at the respective boiling temperatures and atmospheric pressure. The products were subjected to X-ray diffraction analysis, qualitative infrared analysis, differential thermal analysis and microscopic examination. The product obtained in 1.0 M KCl solution was the beta-form of calcium sulphate hemihydrate (alpha-CaSO4. 0.5H(2)O). In more concentrated KCl solution (1.5, 2.0, 2.5, 3.0, 3.5 or 4.0 M), the alpha-form of calcium sulphate hemihydrate(alpha-CaSO4. 0.5H(2)O) was formed, and a reaction took place between KCl and CaSO4, which gave a double salt: potassium pentacalcium sulphate monohydrate (K2SO4. 5CaSO(4). H2O).