Tar

Tar is a dark brown or black viscous liquid of hydrocarbons and free carbon, obtained from a wide variety of organic materials through destructive distillation. Tar can be produced from coal, wood, petroleum, or peat.

Production and trade

In the early 20th century, the term tar referred specifically to a substance derived from the wood and roots of pine. In the United States, the product is often called pine tar. Production and trade in pine-derived tar was a major contributor in the economies of Northern Europe and Colonial America. Its main use was in preserving wooden sailing vessels against rot. The largest user was the Royal Navy. Demand for tar declined with the advent of iron and steel ships.

Tar-like products can also be produced from other forms of organic matter, such as peat. Mineral products resembling tar can be produced from fossil hydrocarbons, such as petroleum. Coal tar is produced from coal as a byproduct of coke production.

Uses

Tar is used in treatment of the skin disease psoriasis, where coal tar is the most effective. Tar is also a general disinfectant. Pine tar is included in some soaps and shampoos.

Safety

Tar is a known carcinogen. Its use in medicinal products is generally safe, but care should be taken to avoid excessive use or contact with the eyes or mouth.

See also

• Coal tar
• Pine tar
• Destructive distillation
• Psoriasis

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