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Coal tar pitch is a byproduct of turning coal into coke or coal gas. It is a sticky, dark brown or black liquid that resists flowing and has a very strong smell. The actual components that make up coal tar pitch vary because the chemicals in the coal it comes from differ. Even so, it coal tar pitch is primarily made up of a wide variety of different phenols and polycyclic aromatic hydrocarbons. While coal tar does have medicinal uses in treating some skin conditions, it is primarily burned as a low-cost fuel or further processed into other materials.
While there may be hundreds of different chemicals in coal tar pitch, phenols and polycyclic aromatic hydrocarbons make up two large classes of chemicals. Phenols are a complex classification of molecules that are typically very caustic and often harmful even in small quantities. Polycyclic aromatic hydrocarbons are dichotomous substances that are both extremely harmful to life and believed to be necessary for life to exist at all. They are present in nearly all air and food to some degree, although the concentration in coal tar pitch is much higher.
The main beneficial property of coal tar pitch is in the treatment of skin diseases such as psoriasis and dandruff. The amount of coal tar in these treatments is very low, as any amount over 5% by volume is considered a health risk and a potential carcinogen. In addition, coal tar pitch is used in the preparation and processing of other drugs, such as acetaminophen.
In most cases, the volume of coal tar pitch used in medicinal preparations is very small in comparison to the amounts produced. As a result, most of the pitch is further processed to remove useful chemicals or is simply burned. The use of coal tar pitch as a power source is questionable, as it burns with a very low heat and produces a lot of smoke, but it is better than not using it at all.
It is possible to create a handful of useful materials from coal tar pitch. One of the main extracted chemicals is creosote, a very widely used wood preservative. In addition, some types of phenols are useful as disinfectants and in the production of plastics. Lastly, the purified tar can be used as an industrial sealant.