Phosphorous acid, an inorganic compound, is highly soluble in water and alcohol. It slowly oxidizes to phosphoric acid in air and decomposes into phosphoric acid and phosphine (highly toxic and explosive) when heated to 180°C. As a dibasic acid, phosphorous acid is slightly stronger than phosphoric acid and possesses strong reducing properties, readily reducing silver ions (Ag?) to metallic silver (Ag) and sulfuric acid to sulfur dioxide. It is highly hygroscopic and deliquescent, with corrosive characteristics. Phosphorous acid is primarily used as a reducing agent, a brightening agent for nylon, as well as a raw material for phosphites, pesticide intermediates, and organic phosphorus water treatment chemicals.