The term<unk> s refers to a group of 3 benzene derivatives which encompasses ortho-, meta-, and para- isomers of dimethyl benzene. The o-, m- and p- isomers specify to which carbon atoms (of the main benzene ring) the two methyl groups are attached. Counting the carbon atoms from one of the ring carbons bonded to a methyl group, and counting towards the second ring carbon bonded to a methyl group, the o- isomer has the IUPAC name of 1,2-dimethylbenzene. The m- isomer has the IUPAC name of 1,3-dimethylbenzene. And p- isomer has the IUPAC name of 1,4-dimethylbenzene.
It is a colorless, sweet-smelling liquid that is very flammable. It occurs naturally in petroleum and coal tar and is formed during forest fires. The chemical properties differ slightly from isomer to isomer. The melting point is between −47.87 °C (−54.17 °F) (m-xylene) and 13.26 °C (55.87 °F) (p-xylene). The boiling point is for each isomer at around 140 °C (284 °F). The density is at around 0.87 kg/L (7.26 lb/U.S. gallon or 8.72 lb/imp gallon) and thus is less dense than water.<unk>  in air can be smelled at 0.08 to 3.7 parts of<unk>  per million parts of air (ppm) and can begin to be tasted in water at 0.53 to 1.8 ppm.
Chemical industries produce<unk>  from petroleum. It is one of the top 30 chemicals produced in the United States in terms of volume.<unk>  is used as a solvent and in the printing, rubber, and leather industries. p-Xylene is used as a feedstock in the production of terephthalic acid, which is a monomer used in the production of polymers. It is also used as a cleaning agent for steel and for silicon wafers and chips, a pesticide , a thinner for paint, and in paints and varnishes.  It may be substituted for toluene to thin lacquers where slower drying is desired. It is found in small amounts in airplane fuel and gasoline.  In animal studies it is often swabbed on the ears of rabbits to facilitate blood flow and collection, although the area must subsequently be cleansed with alcohol to prevent inflammation.
Xylene
Vinyl chloride
Ether
Toluene
Acetylene
Benzene
Coal tar
Nitrazine