Absorption Spectrum of Sulphur Monoxide

Abstract

IN a recent investigation¹, we attempted to detect sulphur monoxide in the photochemical decomposition of sulphur dioxide by examining the absorption spectrum of the latter before and after its irradiation. An absorption spectrum of the monoxide was reported to have been found by P. W. Schenk and H. Cordes² in the spectral region between 3300 A. and 2500 A., and although sulphur dioxide has very strong absorption bands in this region, they found evidence of the spectrum of sulphur monoxide, even when its concentration was 10⁴ times smaller than that of the dioxide³. This spectrum, however, could not be detected in the photochemical decomposition of sulphur dioxide, and it has been assumed¹ that the act of photo-dissociation provides sulphur monoxide with a surplus amount of energy which makes it react instantaneously. But since this surplus amount of energy is only 13 cal. for 1950 A., this conclusion did not seem quite satisfactory. It seemed advisable, therefore, to ascertain whether the absorption spectrum described by Cordes and Schenk was to be attributed to the presence of the monoxide.