The enthalpies of reactions between alkaline-earth cuprates M2CuO3 (M = Ca, Sr) and hydrochloric acid were measured in a hermetic swinging calorimeter at 298.15 K. The M2CuO3 samples were prepared by solid-phase synthesis from calcium or strontium carbonate and copper oxide and characterized by X-ray powder diffraction, EDX and wet analysis. The standard enthalpies of formation obtained for the cuprates, -1431 +/- 4 kJ mol(-1) for Ca2CuO3 and -1374 +/- 3 kJ mol(-1) for Sr2CuO3, are discussed and compared with previous experimental and assessed values. (c) 2005 Elsevier B.V. All rights reserved.