Titrimetric Determination of Phosphorus in Aqueous Solutions of Mo-V-phosphoric Heteropoly Acids and Catalysts Based on Them
Viktor Filagrievich Odyakov, Elena Georgievna Zhizhina
Abstract
The analyzed aqueous solution of Mo-V-phosphoric heteropoly acid is reduced by d,l-tartaric acid (d,l-H2Tart) at room temperature. d,l-H2Tart reduces only vanadium(V) to vanadium(IV). The obtained solution is neutralized by ammonia, then the Mg(NO3)2 solution is added to it giving the NH4[MgPO4]·xH2O precipitate. This precipitate is washed by the triple buffer NH4NO3 + NH3 + (NH4)3HCit solution containing citrate, then by the puffer NH4NO3 + NH3 solution without citrate. Next the precipitate is dissolved in 1.0 M HNO3. The obtained solution is titrated by 0.100 M lead(II) nitrate solution in the acetate buffer in the presence of Cl-–ions using the Pb-selective electrode. In the course of the titration, the Pb5Cl(PO4)3 precipitate is formed.