Spectrophotometric determination of sulfite with soluble mercury(II) compounds

Abstract

Sulfite ion reacts with mercury(II) ion in acid solution to form the mercury(I) ion. The reaction is rapid and quantitative. The mercury(I) ion absorbs at 237 nm with a molar 5 Beer's law Data for Sulfite Complexes of Covalent Mercury(II) Compounds SO 2 (ppm) ϵHgCl 2 a ϵHgBr 2 ϵHg(Ac) 2 b ϵHg(SCN) 2 2.0 12,500 10,000 10,000 9,200 4.0 12,500 11,500 10,000 9,000 6.0 12,500 11,500 10,000 9,200 8.0 12,000 11,000 10,500 9,800 a Molar absorptivity based on sulfite ion at 230 nm. Solution was 6.86 buffer. b Mercuric acetate solutions seemed to be somewhat unstable. absorptivity of about 25,000. The absorbance is linear over a range of approximately 0.5–5.0 ppm as SO 2. Covalent mercury(II) compounds form a complex with sulfite, Hg(SO 3) 2 2−, which absorbs at 230 nm and shows a linear response over a range of 1–8 ppm as SO 2.