Photometric determination of small amounts of oxygen in water with 3,3′-dimethylnaphthidine

Abstract

The oxidation products of manganese obtained in Winkler's classical method for the determination of oxygen can be determined by a photometric method based on their reaction with 3,3′-dimethylnaphthidine in an acidic medium. This reagent is used in preference to o-tolidine because of its higher molecular weight, which results in greater sensitivity, and in the intense red-violet colour of the oxidised form of 3,3′-dimethylnaphthidine.