Molecular-emission spectroscopy in cool flames. Part I. The behaviour of sulphur species in a hydrogen-nitrogen diffusion flame and in a shielded air-hydrogen flame

Abstract

A method is described for the determination of sulphur that involves simple measurement of the S₂ band emission at 384 mµ in a nitrogen-diluted hydrogen diffusion flame burning in air, or in a pre-mixed air-hydrogen flame burning inside a cooled sheath. Sulphuric acid may be determined by this technique in the range 6·4 to 500 p.p.m. of sulphur in the latter flame, or dissolved sulphur dioxide in the range 3·2 to 320 p.p.m. in either flame. The temperature of the flame most suitable for conversion of sulphur species into S₂ is established as 390° C.

The analytical method proposed for sulphates is simpler than the indirect flame-photometric methods hitherto described, and means are suggested whereby the method may be used for the determination of any form of sulphur species. The analytical signal for sulphur varies linearly with the square of the sulphate-ion concentration in the test solution.