Fact sheet: 1,4-xylene (para-xylene)

From: Public Services and Procurement Canada

Discover a list of a contaminant's important chemical properties, how it will react in the environment, main sources of contamination related, and a brief overview of health and safety issues.

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General information

CAS number


Molecular formula


Formula weight

106.2 g/mol


Monocyclic aromatic hdrocarbons (MAH)

Properties (at room temperature where applicable)

Compound properties list
Melting/boiling point -13 °C / 138 °CLiquid
Relative density0.86 g/cm3Floats on water
Vapour pressure8 mm HgModerately volatile
Vapour density3.7Denser than air
Solubility in water160 mg/LLow solubility
Henry's law constant6 x 10-3 atm·m3/molRapid volatilization when dissolved
log Koc (Depending on soil or sediment characteristics)2.3 - 2.7*Moderate adsorption to organic matter

Environmental behaviour

At 20 0C, para-xylene (p-xylene) is a liquid that floats on water and is moderately volatile. Characterized by low solubility, it will volatilize rapidly once dissolved and moderately adsorbs to organic matter. In soil, pure p-xylene can be found as either a solid or liquid (melting point of 13 0C). During a spill, this compound will partially evaporate but the majority of the product will enter into the soil where it may solidify or migrate into a waterway and create a film on the water surface. Solid 1,4-xylene in the soil will dissolve and volatilize slowly. Once dissolved, the majority of 1,4-xylene will volatilize, but may also migrate into the water table. The adsorbed p-xylene in the vadose and saturated zones will take some time to disappear, liberating contamination primarily in the gaseous, or in the dissolved state. The resulting plumes (gaseous or dissolved) will be relatively limited in size.

Health and safety

1,4-Xylene should be handled with care as it is flammable and toxic.

Principal resources

Xylene isomers (ortho-, meta-, and para-) are aromatic hydrocarbons naturally present in crude petroleum and coal tar. Mixed xylene (a mixture of ethylbenzene and the three isomers of xylene, where m-xylene predominates) is produced industrially in large amounts from petroleum or coal tar. Approximately 70 % of mixed xylene is used in the production of ethylbenzene and the o-, m-, and, especially, p- (five times more than any other) isomers of xylene. The remaining mixed xylene is primarily used as a solvent in the printing, rubber and leather industries, in products such as paints and coatings, or blended into airplane fuels and gasoline.

Xylene isomers are used primarily for internal industrial operations as solvents and intermediates in synthetic reactions. o-Xylene is a chemical intermediate in the synthesis of phthalic anhydride (for plasticizers), phthalonitrile, 4,4-(trifluoro-1-(trifluoromethyl) ethylidene) diphthalic anhydride (for polyimide polymers), o-toluic acid, vitamins and pharmaceuticals. m-Xylene is a chemical intermediate in the production of isophthalic acid and isophthalonitrile; isophthalic acid, in turn, is used in the manufacture of polyesters. p-Xylene is a chemical intermediate in the synthesis of terephthalic acid (for polyesters resins and fibers), dimethyl tetrachloroterephthalate, vitamins and pharmaceuticals. Both o-xylene and p-xylene are used as components of insecticides.

Because individual xylene isomers are used in large amounts in industrial settings, people who work or live near these locations may receive a higher exposure to one xylene isomer compared to the other isomers. However, since xylenes are present as a mixture in gasoline and in the solvent components of commonly used commercial products (paint, coatings, etc.), exposure of the general population is expected to be primarily to xylenes as a mixture, and not to the separate xylene isomers. Xylenes may be introduced into groundwater by fuel oil, gasoline or solvent spills, leaking underground petroleum storage tanks, or leaching from disposed wastes.


Agency for Toxic Substances and Disease Registry (ATSDR). 2007. Toxicological Profile for Xylenes. U.S. Department of Health and Human Services, Public Health Service, Georgia, USA. (Viewed December 2013)

Montgomery, John H. 2007. Groundwater Chemicals, Desk Reference, Fourth Edition, CRC Press, Taylor and Francis Group, Florida, USA.