Xylene, xylol or dimethylbenzene is any one of three isomers of dimethylbenzene, or a combination thereof. With the formula (CH3)2C6H4, in each of the three compounds a benzene ring is substituted by two methyl groups. They are all colorless, flammable, slightly greasy liquids. They are of great industrial value. The mixture is referred to as both xylene and, more precisely, xylenes. Mixed xylenes refers to a mixture of the xylenes plus ethylbenzene. The four compounds have identical empirical formulas C8H10. Typically the four compounds are produced together by various catalytic reforming and pyrolysis methods.