Phosphorous acid English name: Phosphorous acid Chemical formula: H?PO? Molecular weight: 82.00 CAS Registry Number: 13598-36-2 EINECS Number: 237-066-7 Melting point: 73.6°C Boiling point: 200°C (decomposes) Density: 1.651 g/cm3 Water solubility: Highly soluble in water Appearance: White or pale yellow crystals with a garlic-like odor Properties: Strong hygroscopicity and deliquescence; easily soluble in water and alcohol. Slowly oxidizes to phosphoric acid in air. Uses: Mainly used as a reducing agent, a brightening agent for nylon, a raw material for phosphites, a pesticide intermediate, and a precursor for organic phosphorus water treatment agents.