sulfurous acid

When sulfur dioxide is dissolved in water, an acidic solution results. This has long been loosely called a sulfurous acid, H₂SO₃, solution. However, pure anhydrous sulfurous acid has never been isolated or detected, and an aqueous solution of SO₂ contains…

…contains sulfite (SO₃²⁻), is called sulfurous acid; and HNO₂, which contains nitrite (NO₂⁻), is named nitrous acid. The acids of the oxy anions of chlorine are used here to illustrate the rules for naming acids with oxygen-containing cations.

Esters of sulfurous acid known as dialkyl sulfites—dimethyl sulfite, MeOS(O)OMe, for example—can be made from alcohols and thionyl chloride: 2MeOH + Cl₂S=O → MeOS(=O)OMe. Cyclic sulfite esters, made in a similar manner from 1,2-diols (1,2-dialcohols), and their oxidation products, cyclic sulfate esters, find considerable use in organic…

These acids, particularly sulfurous acid and sulfuric acid, are of considerable importance to the chemical industry. Sulfurous acid, H₂SO₃, is produced when sulfur dioxide is added to water. Its most important salt is sodium sulfite, Na₂SO₃, a reducing agent employed in the manufacture of paper pulp, in photography,…

Sulfurous acid is generally introduced into the process to prevent the development of various microorganisms.

…dissolve in water to form sulfurous and sulfuric acids. These compounds contribute in large part to the “acid rain” that can kill sensitive aquatic organisms and damage marble monuments and stone buildings.