Applications of Catalytic Reactions. Kinetic Microdetermination of W(VI) and V(V) A kinetic method is described for the microdetermination of tungsten and vanadium. The method is based on the catalytic action of tungstate and vanadate ions on the oxidation of 2,4-diaminophenol with hydrogen peroxide. The effect of reagent concentration is studied and the maximum tolerable amounts of interfering ions are determined. Procedures for the determination of 0.46 to 73.5μg/ml tungsten are given with a relative error of about 1.5%. Quantities of 2.02·10−2 to 2.5μg/ml vanadium could be determined with a relative error of about 2%. Furthermore a kinetic determination of tungstate and vanadate ions in their mixtures is proposed.