PHOSPHORESCENCEMETRY AND ACID-BASE REACTIONS OF VANADIUM-OXIDES IN MOLTEN BISULFATE, DIMETHYLSULFONE AND SOME SOLVENTS

The acid-base reactions of V2O5 in molten NaHSO4-NH4HSO4 equimolar mixtures, KHSO4 melt, dimethylsulfone (DMSO2) melt, concentrated H2SO4 and water were investigated by measuring the phosphorescence spectra. Vanadate ions such as VO3+, VO2+, VO3-, and VO43- in the molten alkaline solvents were discerned from V = 0 bond. The chemical equations for the equilibrium between these ions were confirmed from the variation of phosphorescence spectra as follows; VO2+ + SO3 = VO3+ + SO42- and VO2+ + NO3- = VO3- + NO2+. The phosphorescence peaks of vanadate ions shifted from 475 nm to 680 nm with increasing basicity in bisulfate melts. Similarly, the red shift from 465 nm to 555 nm is regarded as the following reactions in molten DMSO2; KVO2SO4 + DMSO2 = KVOSO4DMSO3 and KVOSO4DMSO2 + KNO3 = KVO2SO4 + KNO2DMSO3. These results showed that the basicity depended on the phosphorescence energy of vanadate ions. The optical basicities estimated from phosphorescence energy of vanadate ions in some solvents were about 0.40 and 0.55 for molten DMSO2 - KVO2SO4 and DMSO2-KNO3-KVO2SO4 at 150-degrees-C, respectively.