Potentiometric determination of the gibbs energies of formation of lead aluminates

Abstract

The Gibbs energies of formation of three compounds in the PbOAl₂O₃ system—2PbO·Al₂O₃, PbOAl₂O₃ , and PbO· 6A1₂0₃—have been determined from potentiometric measurements on reversible solid‐state galvanic cells Pt, Ir I Pb,αAl₂O₃, PbO ·6A1₂0₃ I ZrO₂CaO I NiO, Ni I Pt Pt I NiO, Ni I ZrO₂CaO I Pb, PbO·6A1₂0₃, PbO· A1₂0₃ I It, Pt and Pt I NiO, Ni I ZrO₂CaO I Pb, PbO·A1₂O₃, 2PbO·Al₂O₃ It, Pt in the temperature range 850–1375 K. The results are discussed in the light of reported phase diagrams for the PbOA1₂0₃ system. The partial pressures of different lead oxide species, PbnOn, n = 1−6, in the gas phase in equilibrium with the aluminates are calculated by combining the results of this study with the mass‐spectrometric data of Drowart et al.(1) for polymerization equilibria in the gas phase. The concentration of oxygen in lead in equilibrium with the aluminates are also derived from the results and the literature data on the Gibbs energy of solution of oxygen in liquid lead.