Chlorous acid

Chlorous acid is a chemical compound with the formula HClO2. It is a weak acid. The pure substance is unstable, degrading to chloride, chlorate and chlorine dioxide. But chlorites salts such as sodium chlorite are stable conjugate bases derived from this acid. These salts are sometimes used in the production of chlorine dioxide.

HClO2 can be prepared through reaction of barium chlorite and dilute sulfuric acid:
 * Ba(ClO2)2 + H2SO4 → BaSO4 + 2HClO2