AbstractKinetics of oxidation of indigo carmine (IC) by sodium hypohalites, NaOX (X  Cl or Br), in alkaline buffer of pH 9–11 has been studied spectrophotometrically at λ = 610 nm. The experimental rate law obtained is −d[IC]/dt=k[OX−][IC][OH−]xwherex<1. Variation of ionic strength or dielectric constant of the medium had no effect on the reaction rate while the addition of halide ions slightly retarded the rate. A most plausible mechanism proposed on the basis of experimental results involves the formation of isatin sulphonate which undergoes further oxidation to anthranilate. Activation parameters have been