The use of the Nb-Nb2O5 electrode as an indicator electrode in potentiometric acid-base titrations in fused KNO3

Abstract

An Nb-Nb₂O₅ electrode was prepared by the electrolytic oxidation of niobium in molten KNO₃. This electrode can be used as an indicator electrode in potentiometric acid-base titrations. It behaves reversibly and responds theoretically to the oxide ion concentration in molten KNO₃. Its potential varies linearly with ln[O^2-] and the line has a slope of 68 mV at 350 °C. The standard potential of the Nb-Nb₂O₅, O^2- electrode, i.e. the potential at [O^2-] = 1, is computed as -810 mV with respect to the Ag-Ag⁺ reference electrode.