The kinetics of the oxidation of methylene blue by permanganate ion has been studied in aqueous acidic medium. The rate of the reaction was found to be acid dependent and first order in both oxidant and reductant. The emprical rate law conforms to the equation: ‘a’ = 4.04 x10-3 dm3 mol-1 s-1 and ‘b’ = 0.125 dm6 mol-2 s-1: at [H+] = 1 x 10-3 mol dm-3, μ= 0.25 mol dm-3 (Na2SO4), λmax = 660 nmand T = 24 ± 1.0°C. The rate of reaction decreases with increase in ionic strength. Added ions and decrease in medium dielectric constant inhibited the reaction rates. The mechanism of reaction has been rationalized on the basis of both the outer-sphere and the inner-sphere pathways based on spectroscopic investigation and kinetic evidence.
