Hypochlorous acid

Hypochlorous acid is a weak, unstable acid with chemical formula HOCl. It occurs only in solution and is used as a bleach, an oxidizer, a deodorant, and a disinfectant.

In aqueous solution, hypochlorous acid partially decomposes into the hypochlorite anion ClO^- (also known as the chlorate(I) anion) and the proton H⁺. The salts of hypochlorous acid are also called hypochlorites. One of the best known hypochlorites is household bleach, sodium hypochlorite (NaClO).

When pure chlorine is added to water, it forms hypochlorous acid and hydrochloric acid (HCl):

Cl₂ + H₂O → HOCl + HCl

Hypochlorous acid (HOCl) is the stronger form of free chlorine, and hydrochloric acid (HCl) lowers pH and alkalinity.

In biology, hypochlorous acid is used by neutrophiles to kill bacteria.