Benzene is a hydrocarbon organic compound, the simplest aromatic hydrocarbon. Its molecular formula is C₆H₆. It is a sweet, flammable, carcinogenic and colorless transparent liquid at room temperature with a strong aromatic odor. It is hardly soluble in water and easily soluble in organic solvents. It can also be used as an organic solvent itself. The ring system that benzene has is called benzene ring, and the structure after removing one hydrogen atom of benzene ring is called phenyl, which is represented by Ph. Therefore, the chemical formula of benzene can also be written as PhH. Benzene is a basic raw material for petrochemical industry, and its output and technical level of production are one of the signs of a country's petrochemical development level.