Mathematical modeling and analysis of equilibria in Nb(5) solutions

Studying of the processes of polycondensation in aqueous solutions of Nb(5) compounds by the methods of pH-metry, spectrometry and mathematical modeling shows that at low Nb(5) ion concentration (2.0·10-4-0.5·10-4 mol/l) H2Nb12O3610- dodecaniobate-ions appearing by dimers of H3Nb6O195- ions are present. Results of mathematical modeling od series with different Nb(5) ion concentration evidence that the process of dimerization is depended on Nb(5) concentration. Acidification of the solutions leads to formation of more protonated forms the most stable of which are H7Nb12O365- and H10Nb12O362-. Introduction even insignificant quantities of alkali leads to quick transition of dodecaniobate-ions in hexaniobate-ions. In strong alkali solutions dodecaniobate- and hexaniobate-ions decompose in tetrameric and monomeric forms. The scheme describing polycondensation processes in aqueous Nb(5) solutions after distinguishing of equilibrium is proposed