ABSORPTION OF SULFUR-DIOXIDE IN DILUTE AQUEOUS-SOLUTIONS OF SULFURIC AND HYDROCHLORIC-ACID

Spectrophotometric measurements of combined phase and chemical equilib rium have been performed for SO2 + H2SO4 + H2O and SO2 + HCl + H2O sys tems at 298 K and atmospheric pressure. The vapour and liquid phases h ave been analysed in situ using a fibre optic based technique describe d in an earlier publication. The measurements have been performed up t o an equilibrium partial pressure of about 1 kPa for sulfur dioxide. T he concentration range of the acids have been varied up to 0.5 M for H 2SO4 and 1.0 M for HCl. A thermodynamic model is presented which allow s the interpolation and the extrapolation of the experimental results. The calculated partial pressures of SO2 in the SO2 + H2SO4 + H2O syst em are compared with existing literature values. The experimental resu lts for the SO2 + HCl + H2O system show an anomaly in the uv-spectrum of molecular dissolved sulfur dioxide. The absorption band for SO2 is shifted towards higher wavelength. This effect is interpreted in terms of the formation of a weak complex SO2Cl-. (C) 1997 Elsevier Science B.V.