The chemical name of acetaminophen is N - (4-hydroxyphenyl) acetamide, with the trade name paracetamol. It belongs to the acetanilide class of antipyretic and analgesic drugs. It was first synthesized by Morse in 1878 and first used in clinical practice by VonMering in 1893. It became an over-the-counter drug in the United States in 1955, and production began in China in the late 1950s. Its appearance is white crystalline or crystalline powder, with a melting point of 168-172 ℃. It is odorless, slightly bitter in taste, easily soluble in hot water or ethanol, soluble in acetone, and almost insoluble in cold water and petroleum ether. Stable below 45 ℃, but if exposed to humid air, it will hydrolyze into para aminophenol, which then undergoes further oxidation and gradually turns pink, brown, and finally black. Therefore, it should be stored in a cool and dry place in a sealed manner.