The molecular and chemical formula for sulfurous acid is H2O3S. It's created when sulfur dioxide dissolves in water. As of 2014, it has been detected in the gas phase, but there is no evidence of its existence in solution.
Sulfurous acid is clear, colorless and smells sulfurous. It ignites at a set temperature. It's a weak acid that transforms into sulfuric acid upon exposure to the atmosphere. Sulfuric acid has harmful effects, such as joining with rain to create acid rain, which damages plants and other life forms. Sulfurous acid can be used as a mild bleach for substances that can't handle chlorine.