Hypochlorous acid is a chemical compound. Its chemical formula is HClO or HOCl. It is not stable. It contains chlorine in its +1 oxidation state. It is a powerful oxidizing agent. It is made by reacting sodium hypochlorite with an acid that cannot be oxidized, such as phosphoric acid. If the acid can be oxidized, the hypochlorous acid will be destroyed. It is used to make some chemicals. It breaks down into hydrochloric acid and oxygen in sunlight. It reacts with hydrochloric acid to make chlorine gas. It is a powerful disinfectant.