Promethazine hydrochloride as a new redox indicator in vanadametry

Promethazine hydrochloride is proposed as a new redox indicator in vanadametry. It has been tested rigorously in the titration of iron(II), hydroquinone, uranium(IV) and antimony(III) with sodium vanadate. The indicator gives a very sharp reversible colour change from green to violet at the equivalence point. It has advantages over all the proposed redox indicators in vanadametry. Its redox and transition potentials are reported.