CHROMIUM(III)-CATALYZED OXIDATION OF ANTIMONY(III) BY ALKALINE HEXACYANOFERRATE(III) AND ANALYSIS OF CHROMIUM(III) IN MICROAMOUNTS BY A KINETIC METHOD

The oxidation of antimony(III) by hexacyanoferrate(III) has been studied in alkaline media. A microamount of chromium(III) (10(-6) mol dm(-3)) is sufficient to catalyse the reaction. The active species of catalyst and oxidant in the reaction are understood to be [Cr(OH)(4)](-) and [Fe(CN)(6)](3-). The autocatalysis exhibited by one of the products, i.e, antimony(v), is attributed to complex formation between antimony(v) and [Fe(CN)(6)](3-). A composite mechanism and rate law are proposed. The reaction has been utilised for the analysis of chromium(III) in the range 5.2 ng cm(-3)-1.14 mu g cm(-3).