Mathematical modeling of pH-potentiometric measurements in tungsten-vanadium solutions

Models of polycondensation in acidified solutions containing HVO42- and WO42- ions were developed. The models were demonstrated to adequately describe pH-potentiometric titration measurements in dilute solutions (cdegrees(V+W) = 10(-3) mol/l) at V:W ratios of 1:5, 2:4, 3:3, 4:2, and 5:1. Distributions of poly and isopoly anions of vanadium(V) and tungsten (VI) were constructed over the pH range 3-10 (Z = 0-3.50) against the background of nitrate ions. It is shown that, in dilute solutions, isopoly tungstenovanadates of the sixth row, which retain the initial ratio V:W are predominantly formed. The concentration constants of formation of poly(tungsten-vanadium) anions in aqueous solutions were determined.