Potentiometric Titration of NH4VO3 and Na2HAsO4 in Molten NaNO3 at 623 K Using a Novel Solid-State Glass/Nb2O5 pH Indicator Electrode

A solid state glass/Nb2O5 electrode was prepared by the sol-gel process using the sonocatalytic method. The film reported here was prepared from an NbCl5 as precursor and butanol as solvent. The relation between log [O2-] and glass/Nb2O5 electrode potential in molten KNO3 at 623 K is linear with a slope of 59.1 mV at 623 K. This value is closer to the theoretical value 2.303 RT/F (61.6 mV at 623 K). The standard potential of this electrode, E-0, is computed as -984.7 mV relative to the Ag/Ag reference. The electrode was investigated as an oxide ion indicator electrode in potentiometric titrations between acids and bases in fused salts. This electrode behaves reversibly and responds to the oxide ion concentration in molten nitrate. Two oxide ion acceptors (acids), NH4VO3 and Na2HAsO4, were titrated with oxide ion donors (bases) in fused KNO3 at 625 K. The electrode was found to serve as an excellent indicator for acid base potentiometric titrations in molten salts.