Kinetic study of the oxidation of indigocarmine by hydrogen peroxide with ferrous and ferric ions in acid medium

The use of hydrogen peroxide in addition to ferrous and ferric salts has been shown an effective method in the decoloration of indigocarmine (IDS), Indigo-5,5′-disulfonic acid disodium salt. The kinetic experiments control have been carried out by means of a conventional spectrophotometric technique. In acid medium and the initial absence of Fe+2, the decoloration process obeys the following rate law: Effects of reagents concentrations, temperature, and acidity on the rate experimental constant have been discussed. A feasible reaction mechanism is finally proposed. The rate equation deducted from the mechanism is according to the achieved experimental results. © 1997 John Wiley & Sons, Inc.