Electrometric Titration of Sulfurous Acid with Permanganate

The purpose of this work was to determine whether sulfurous acid in acid solution is completely oxidized to sulfuric acid by an excess of permanganate as stated in the literature. If so the excess of permanganate should be easily and accurately determinable electrometrically with potassium iodide thus giving a simple method for determining sulfur dioxide, sulfurous acid or sulfites. The results show that with a small or large excess of permanganate only about 90 per cent is oxidized to sulfuric acid, the remainder of the sulfurous acid probably forming dithionic acid