The oxidation reaction of antimony(III) with potassium dichromate has been investigated radiometrically. The quantitative
oxidation of antimony(III) was found to be not disturbed even in large amounts of tin(IV). On the basis of these results the
redox substoichiometric isotope dilution analysis using potassium dichromate as the oxidizing agent was proposed for the determination
of antimony in metallic tin. The antimony content of 1.22±0.05 μg in metallic tin (10 mg) was determined without separation
of the matrix element.