Potentiometric Titration of ${\rm NH}_{4}{\rm VO}_{3}$ and ${\rm Na}_{2}{\rm HAsO}_{4}$ in Molten ${\rm NaNO}_{3}$ at 623 K Using a Novel Solid-State Glass/${\rm Nb}_{2}{\rm O}_{5}$ pH Indicator Electrode

Abstract

A solid state glass/Nb 2 O 5 electrode was prepared by the sol-gel process using the sonocatalytic method. The film reported here was prepared from an NbCl 5 as precursor and butanol as solvent. The relation between log [O 2− ] and glass/Nb 2 O 5 electrode potential in molten KNO 3 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), NH 4 VO 3 and Na 2 HAsO 4 , were titrated with oxide ion donors (bases) in fused KNO 3 at 625 K. The electrode was found to serve as an excellent indicator for acid base potentiometric titrations in molten salts.