Investigation of formation of high-vanadium vanadotunstophosphate heteropoly compounds (PVW-HPC) in solution by 31P, 51V NMR-method

Ions, formed in the series of solutions of sodium phosphate, vanadate, taken in the ratio P:V:W=1:6:6, 1:8:4, 1:10:2, are studied, Using the method of NMR spectroscopy on 31P and 51V nuclei. It is shown that the composition of vanadotungstophosphate heteropoly compounds (PVW-HPC) in solutions of each series depends on the degree of their acidification. Two pH ranges of solutions, differing in the character of the complexes formed in them, are pointed out. In pH range -6 a mix8ture of low-vanadium and high-vanadium PVW-heteropolyanions of unsaturated series is formed. At pH below 3 there is a mixture of PVW-HPC of saturated series. It is shown that no PVW-complex of uniform composition is formed in solutions