A discontinuous method has been developed for the simultaneous determination of H2S and SO2 in flue gases. The method is based on a pure gas phase separation whereby H2S is adsorbed on a silica gel column impregnated with silver-sulphate (Ag2SO4) and potassium-hydrogensulphate (KHSO4), while SO2 is subsequently absorbed in a wash-bottle containing a slightly acidic hydrogen peroxide solution. Owing to the acid properties of the impregnated gel, SO2 passes through the column. The experiments show that the penetration of SO2 is quantitative while H2S is adsorbed quantitatively on the column. The method permits the determination of amounts of H2S in the range of 1-1500 mgNm-3 with a sampling time of 5 min and a gas flow of 0.2-4.0 1. min-1. The lower limit for the determination of SO2 under the above conditions lies at about 1 mgNm-3. The separation of H2S and SO2 is not influenced by the presence of moderate amounts of water but the interference of ammonia is more serious. Ammonia is adsorbed on the column and the properties of the gel are changed so that SO2 is also adsorbed. The method is still however, valid for H2S. The interference from organic sulphur compounds is negligible with the procedure. Hitherto the method has successfully been used to analyse H2S in ambient air in the ppb-range as 24-hr mean values. © 1967.
