Enthalpy of formation of natural hydrous copper sulfate: Chalcanthite

Abstract This paper presents the results of the thermochemical study of hydrous copper sulfate CuSO 4 ·5H 2 O performed on a high-temperature heat-flux Tian–Calvet microcalorimeter. The samples of two natural chalcanthite (Kosmurun ore deposit, Kazakhstan, and Lavrion deposit, Greece) and synthetic hydrous copper sulfate (blue vitriol) were characterized by X-ray microprobe analysis, X-ray powder diffraction, thermal analysis, FTIR and Raman spectroscopy. The enthalpy of dehydration at T  = 298.15 K was measured, and the standard molar enthalpies of formation from the elements were determined by the melt solution calorimetry in accordance with Hess’s law. The values of Δ f H m 0 ( T  = 298.15 K) were found to be −(2267.2 ± 4.1) kJ⋅mol −1 for natural chalcanthite and −(2272.6 ± 6.0) kJ·mol −1 for synthetic hydrous copper sulfate (blue vitriol).