COAL TARS Meaning and
Definition
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Coal tars are thick, viscous, and dark brown to black semi-solid or liquid substances that are produced as byproducts of the carbonization or destructive distillation of coal. They are composed of complex mixtures of hydrocarbons, derived primarily from the high temperature heating of coal.
Coal tars contain various organic compounds, including aromatic hydrocarbons, phenols, and heterocyclic compounds. Their composition can vary widely depending on the coal source and the specific process used to produce them. However, they typically consist of three major components: pitch, cresols, and naphthalene.
Pitch, the highest molecular weight fraction of coal tar, is sticky and has a high carbon content. Cresols are a group of aromatic organic compounds that possess phenolic properties and contribute to the toxic and irritating nature of coal tars. Naphthalene is a polycyclic aromatic hydrocarbon that is commonly found in coal tars and gives them their characteristic odor.
Coal tars have historically been used in various industrial applications, such as the manufacturing of roofing materials, pavement sealants, and asphalt products. They have also been used medicinally as topical treatments for skin conditions due to their antiseptic and keratolytic properties. However, due to their high levels of toxic and carcinogenic compounds, the use of coal tars has become highly regulated and restricted in many countries.
In summary, coal tars are complex mixtures of hydrocarbons produced from coal carbonization. They have various industrial applications but are also known for their toxic and carcinogenic properties.
Etymology of COAL TARS
The term "coal tar" is a compound noun composed of "coal" and "tar". Here is the etymology of each component:
1. Coal: The word "coal" originated from the Old English word "col", which can be traced back to Proto-Germanic "kula" and Proto-Indo-European "g(e)u-lo-". It is believed to have originated from the Proto-Indo-European root word "gel-", meaning "to burn" or "shine". Over time, the spelling and pronunciation of "col" evolved into "coal" in Middle English.
2. Tar: The term "tar" comes from the Old English word "teru", which is related to Old High German "tar" and Old Norse "tar". The origin of "tar" can be traced back to the Proto-Indo-European root "tār-", meaning "black" or "dark".
