Sulfur Dioxide SO2 Industrial Gases CAS No.: 7446-09-5 EINECS No.: 231-195-2 UN No.: UN1079 Purity: 99.9% Dot Class: 2.3 Appearance: Colorless Liquid Grade Standard: Industrial Grade Precursor to sulfuric acid: Sulfur dioxide is an intermediate in the production of sulfuric acid, being converted to sulfur trioxide, and then to oleum, which is made into sulfuric acid. As a preservative reducing agent: Sulfur dioxide is sometimes used as a preservative for dried apricots, dried figs, and other dried fruits, it is also a good reductant. As a refrigerant: Being easily condensed and possessing a high heat of evaporation, sulfur dioxide is a candidate material for refrigerants.