Phosphorus(III) oxide, also known as phosphorus trioxide, is a chemical compound. Its chemical formula is P2O3 or P4O6. It contains phosphorus in its +3 oxidation state. It contains phosphorus and oxide ions.
It is a white, waxy solid that can absorb water. It reacts with water to make phosphorous acid. It reacts with hydrochloric acid to make phosphorus trichloride and phosphorous acid. It is a reducing agent. It is toxic and has a garlic-like odor.
It is made by burning phosphorus in a little air. This is the source of many phosphorus compounds.
It can attach to certain transition metals.