The use of the Nb-Nb2O5 as an oxide ion indicator electrode in fused salts

The use of the Nb-Nb₂O₅ electrode as an oxide ion indicator electrode in potentiometric titrations between acids and bases in fused salts was investigated. Two oxide ion acceptors (acids), NaPO₃ and Na₄P₂O₇ were titrated with oxide ion donors (bases) in fused KNO₃. The reaction was carried out at 625 K and the bases used in these titrations are K₂CO₃ and Na₂O₂. The electrode was found to serve as an excellent indicator for acid base potentiometric titrations in fused salts. It serves also as an oxide ion indicator for the titration of mixtures of acids in which chemical transformations are taking place during the course of titration. The experimental results were discussed in terms of the potential arrests and potential shifts upon the addition of the oxide ion donor to the acid.