H₃PO₃, known as phosphorous acid, is a chemical compound composed of three hydrogen atoms, one phosphorus atom, and three oxygen atoms. It is a colorless, syrupy liquid that is often used in agriculture as a fertilizer and in the production of phosphite salts. Phosphorous acid is a weak acid and can act as a reducing agent in various chemical reactions. In addition to its agricultural uses, H₃PO₃ is also important in the manufacturing of certain chemicals and in the food industry as a preservative. It is distinct from phosphoric acid (H₃PO₄), which has different properties and applications. Both acids are related to the element phosphorus, which is essential for life.