KINETICS AND MECHANISM OF REACTION OF ACRIDINE-ORANGE WITH BROMATE ION AT LOW PH

The reaction between acridine orange hydrochloride [3,6-bis(dimethylam ino)acridine hydrochloride] and potassium bromate in dilute sulphuric acid was studied by monitoring the absorbance change at 492 nm. The re action exhibited complex kinetic behaviour. In excess bromate the reac tion had an induction period with slow depletion of acridine orange (A C) followed by a fast depletion step, The initial-reaction step was fo und to be first order with respect to both AC and bromate and second o rder with respect to H+. The stoichiometric ratio of AC to bromate was 3:2. At the end of the induction period, the redox potential of the r eaction mixture has shown a distinct rise, while the Br- concentration dropped sharply. The dual role of bromide ion both as an inhibitor an d autocatalyst is discussed. A 16-step reaction mechanism is proposed and the simulated curves agreed well with the kinetic curves.