An investigation of the products of pyrolysis in the determination of oxygen in sulphur-containing organic substances

Abstract

In theUnterzaucher method for determination of the oxygen in organic substances, erroneous results are obtained with sulphur-containing compounds. A systematic study of the method was therefore undertaken, starting with an investigation of the reaction products formed during pyrolysis using mainly gas chromatography as the analytical tool. Six different sulphur-containing organic compounds were pyrolysed in a quartz tube at 900°, 1000° and 1120°. The amounts of H2S, COS, SO2 and CS2 were measured, and the amount of elemental sulphur was calculated by difference. The same compounds were also pyrolysed in contact with carbon at 1120°. In this case the sulphur was converted mainly to H2S, CS2 and elemental sulphur, although in some cases as much as 2–3% of the sulphur was obtained as COS. A small amount of CH4 was also formed during pyrolysis in contact with carbon. As model substances, thiantrene and thiosalicylic acid were pyrolysed. Analysis of the sulphur compounds formed with differing amounts of test substance yielded results which agreed satisfactorily with those predicted from known equilibrium constants.