The standard enthalpies of formation of the HgBa2CuO4+delta (delta=0.02, 0.08, and 0.11) superconducting phase and Ba2CuO3.05

The enthalpies of reactions of the HgBa2CuO4 + delta phases with various ox ygen indices (delta = 0.02, 0.08, and 0.11), Ba2CuO3.05, and red mercury ox ide with hydrochloric acid were measured in a hermetic swinging calorimeter at 298.15 K, The obtained and literature data were used to calculate the s tandard enthalpies of formation of the specified phases from the elements a nd the metal oxides. The dependence of the enthalpy of formation of the sup erconducting phase on the oxygen index and the partial enthalpy of solution of oxygen in this phase were determined. The thermodynamic stability of th e HgBa2CuO4 + delta, phase at 298.15 K with respect to its possible decompo sition to Ba2CuO3 (+ x). and HgO(red) was estimated.