Benzene. Computer model of a molecule of benzene. Atoms are represented as spheres and are colour- coded: carbon (blue) and hydrogen (gold). Benzene is a highly flammable colourless liquid with a characteristic smell. It is obtained commercially from petroleum. Benzene is used as an additive in petrol, to manufacture other chemicals, and as a solvent for many simple organic compounds. Benzene is a carcinogen, with long-term exposure causing leukaemias (cancers of blood cells).