# What is "sulfurous acid"?

Sulfurous acid is supplied as an aqueous solution labelled ${H}_{2} S {O}_{3}$. It has smell that is not entirely unpleasant; I tend to like it because it has a clean, medicinal smell. It could equally be represented as ${O}_{2} S \cdot {H}_{2} O$, i.e. the water adduct of $S {O}_{2}$. Both $S {O}_{2}$ and $S {O}_{3}$ have some water solubility, and are the acid anhydrides of sulfurous and sulfuric acid.