Dissolution enthalpies of Bi(2)O(3), PbO, SrCO(3), CaCO(3), CuO and Bi(1.7)Pb(0.3)Ca(2)Sr(2)Cu(3)O(10) at 323.15 K in 6 M HCI were measured by solution calorimetry. On the basis of these data, the enthalpies of the following reactions were obtained: (1) 0.85Bi(2)O(2) (s) + 0.3PbO (s) + 2CaCO(3) (s) + 2SrCO(3) (s) + 3CuO (s) + 0.075 O(2) (g)=Bi(1.7)Pb(0.3)Ca(2)St(2)Cu(3)O(10) (s) + 4CO(2); (2) 0.85 Bi(2)O(3)(s) + 0.3PbO (s) + 2CaO (s) + 2SrO (s) + 3CuO (s) + 0.075 O(2) (g)=Bi(1.7)Ph(0.3)Ca(2)Sr(2)Cu(3)O(10) (s). It was established that Bi(1.7) Pb(0.3)Ca(2)Sr(2)Cu(3)O(10) was thermodynamically unstable with respect to the interaction with CO(2) and thermodynamically stable with respect to decomposition to the mixture of binary oxides. The standard formation enthalpy of Bi(1.7)Pb(0.3)Ca(2)Sr(2)Cu(3)O(10) was calculated as following: Delta(f)H (Bi(1.7)Pb(0.3)Ca(2)Sr(2)Cu(3)O(10), 298.15 K)= -3643.3 +/- 8.7 kJ mol(-1) (C) 2011 Elsevier B.V. All rights reserved.