Standard Enthalpies of Formation of the Bi₂Mo₃O₁₂, Bi₆Mo₂Te₂O₂₁, and Bi₂Te₂O₈ Complex Oxides

The tellurium molybdenum bismuth complex oxides Bi₂Mo₃O₁₂, Bi₆Mo₂Te₂O₂₁, and Bi₂Te₂O₈, promising starting materials for the preparation of bismuth-containing tellurite–molybdate glasses, have been synthesized by heating accurately weighed amounts of orthotelluric acid and ammonium heptamolybdate and bismuth nitrate crystal hydrates and identified by X-ray diffraction. Using reaction calorimetry, the standard enthalpies of formation of the complex oxide have been determined to be −2940.3 ± 39.8 kJ/mol for Bi₂Mo₃O₁₂, −4128.6 ± 66.2 kJ/mol for Bi₆Mo₂Te₂O₂₁, and −1383.3 ± 11.5 kJ/mol for Bi₂Te₂O₈. These values have been calculated as the difference between the standard enthalpies of solution of the complex oxide and mixtures of constituent binary oxides of corresponding content in concentrated hydrochloric acid.