Maleic anhydride, also known as “maleic anhydride”, is the anhydride of maleic acid. It is a colorless or white solid with a sour taste at room temperature, with a molecular formula of C4H2O3. Molecular weight 98.06. Needle-shaped crystals are obtained from chloroform or ether. Melting point 60℃, boiling point 82℃ (1.Chemicalbook8665kPa), relative density 1.31460. Soluble in acetone, chloroform, ether, slightly soluble in petroleum ether. Dissolved in water to form cis-butenedioic acid, dissolved in alcohol to form esters, and can react with compounds containing conjugated double bonds to form diene synthesis. Toxic, strongly irritating to mucous membranes.