The standard molar enthalpies of formation of PbBi12O19(s) and ϕ-Pb5Bi8O17(s) by solution calorimetry

Highlights: • ${\Delta }_f{H}_{298}^o$ of PbBi₁₂O₁₉(s) and ϕ-Pb₅Bi₈O₁₇(s) were determined. • Dissolution was carried out in an acid solution isoperibol calorimeter. • Nitric acid (aq., 4.47 mol kg⁻¹) is used as the calorimetric solvent. The standard molar enthalpies of formation of PbBi₁₂O₁₉(s) and ϕ-Pb₅Bi₈O₁₇(s) at 298.15 K were determined using an isoperibol calorimeter. The enthalpies of solution of ternary compounds, namely, PbBi₁₂O₁₉(s) and ϕ-Pb₅Bi₈O₁₇(s) as well as stoichiometric oxide mixtures, namely, {PbO(s) + 6 Bi₂O₃(s)} and {5 PbO(s) + 4 Bi₂O₃(s)} in HNO₃ (aq., 4.47 mol kg⁻¹) at T = 298.15 K were measured. Using these values, ${\Delta }_f{H}_m^o$ (298.15 K) of PbBi₁₂O₁₉(s) and ϕ-Pb₅Bi₈O₁₇(s) were determined as (-3549.6 ± 23.8) kJ mol⁻¹ and (-3239.4 ± 7.6) kJ mol⁻¹, respectively. The given uncertainties were calculated as 2σ of the mean with 0.95 level of confidence.