Coal tar

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Coal tar is a brown or black liquid of high viscosity, which smells of naphthalene and aromatic hydrocarbons. Coal tar is among the by-products when coal is carbonized to make coke or gasified to make coal gas. Coal tars are complex and variable mixtures of phenols, polycyclic aromatic hydrocarbons (PAHs), and heterocyclic compounds. It is a mixture of about 200 substances. [1]

Contents

Applications

Industrial

Being flammable, coal tar is sometimes used for heating or to fire boilers. Like most heavy oils, it must be heated before it will flow easily.

Tar was a vital component of the first sealed, or "tarmac", roads. The streets of Baghdad were the first to be paved with tar from the 8th century AD.[2] Coal tar was formerly used as one of the primary ingredients of Tarmacadam pavements, when mixed with ironworks slag. [3] Today, petroleum derived binders and sealers are more commonly used. These sealers are used to extend the life and lower maintenance cost associated with asphalt pavements, primarily in asphalt road paving, car parks and walkways.

Medical

Like pine tar, it can be used in medicated shampoo, soap and ointment, as a treatment for dandruff and psoriasis, as well as being used to kill and repel head lice. When used as a medication in the U.S., coal tar preparations are considered an OTC (over-the-counter drug) pharmaceutical and are subject to regulation by the United States Food and Drug Administration. Name brands include Denorex, Balnetar, Psoriasin, Tegrin, T-Gel, and Neutar. When used in the extemporaneous preparation of topical medications, it is supplied in the form of Coal Tar Topical Solution USP, which consists of a 20% w/v solution of coal tar in alcohol, with an additional 5% w/v of polysorbate 80; [4] this must then be diluted in an ointment base such as petrolatum. Coal tar is also used to synthesize paracetamol (acetaminophen). It is also used to manufacture paints,synthetic dyes and photographic materials.

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