A titrimetric study of the reaction of quinones in fluoride solution with iron(II)

Abstract

A simple, direct potentiometric titration is described for the determination of the percentage purity of quinones. The quinone, 0·25 to 1 mmole, is dissolved in 50 per cent. v/v aqueous alcoholic solution, which is 0·5 M in hydrofluoric acid and 0·5 M in ammonium fluoride, then titrated with a standardised solution of ammonium iron(II) sulphate. Results are presented for the titration of ten quinones and it has been established that any quinone, which forms part of a couple whose formal electrode potential in the aqueous alcoholic mixed fluoride solution is not less than +0·24 V versus the normal hydrogen electrode, can be determined. These quinones include almost all of the 1,4-benzoquinones, 1,2-benzoquinones and phenanthraquinones, many naphthaquinones, but only a few anthraquinones.