Kinetics and mechanism of oxidation of arsenic(III) by quinolinium dichromate(QDC) in aqueous perchloric acid

Abstract

The kinetics of oxidation of arsenic(III) by quinolinium dichromate(QDC) has been investigated spectrophotometrically over a wide range of arsenic(III) concentrations in aqueous perchloric acid medium and at a constant ionic strength. As the arsenic(III) concentration varies, from lower concentration region to higher one, the order with respect

to [arsenic(III)] changes from first to zero order. In all the regions of the [arsenic(III)], the reaction is first order in [oxidant] and less than unit order in [acid] . Increase in [perchloric acid] accelerates the reaction rate. The added products, chromium(III) and arsenic(V) do not significantly affect the reaction rate. A suitable mechanism is proposed and the involved reaction constants have been evaluated. Activation parameters have also been calculated.