FT-IR SPECTROSCOPIC MONITORING OF ALKALI-METAL DISULFITE AND HYDROGENSULFITE IN FREEZE-CONCENTRATED AND GLASSY AQUEOUS-SOLUTION - IMPLICATIONS FOR ATMOSPHERE CHEMISTRY

FT-IR spectra of aqueous potassium hydrogensulfite solutions, with nom inal concentrations between 0.1 and approximate to 3.6 mol(-1), were r ecorded as aqueous and freeze-concentrated solution from 295 to 230 K (from 4000 to 950 cm(-1)) and as glassy solution at 78 K (from 4000 to 400 cm(-1)). Whereas disulfite is only a minor species in dilute hydr ogensulfite solution, it becomes the major S(IV) species on formation of ice and subsequent freeze-concentration of the solute. Condensation to disulfite can be avoided by ''hyperquenching'' dilute aqueous hydr ogensulfite solution into the glassy state. On heating in vacuo up to 200 K, only partial condensation was observed and solid KHSO3 was isol ated. We conclude that at the low temperatures existing in the troposp here, these further S(IV) species have to be considered in the oxidati on of acidic SO2 containing dilute aqueous solution to sulfuric acid. (C) 1997 Elsevier Science B.V.