Simultaneous kinetic thermometric determination of V(V) and W(VI) traces by the inhibitory effect of W(VI) on the V(V)-catalysed oxidation of thiosulphate ion by hydrogen peroxide

Summary A new method for the simultaneous kinetic thermometric determination of V(V) and W(VI) traces based on the inhibitory effect of the latter ion on the catalytic action of the former on the oxidation of thiosulphate ion by hydrogen peroxide was developed. A universal mathematical model for the kinetics of the process which includes the catalytic and inhibitory effects of the species involved and relies on the standard-addition and Newton-Gauss methods facilitates the determination. The applicability ranges of the proposed method are 0.1–0.8 ppm V(V) and 1–14 ppm W(VI). The method is subject to few interferences, of which those from Fe(III) and Mo(VI), which also catalyse the analytical reaction, are the most serious.