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Coal tar
 
 
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Coal tar is a brown or black liquid of high viscosity
Viscosity

Viscosity is a measure of the Drag of a fluid which is being deformed by either shear stress or extensional stress. In everyday terms , viscosity is "thickness"....
, which smells of naphthalene
Naphthalene

Naphthalene, also known as naphthalin, naphthaline, tar camphor, white tar, albocarbon, or antimite and not to be confused with naphtha, is a crystalline, Aromaticity, white, solid hydrocarbon with formula Carbon10hydrogen8 and the structure of two fused benzene rings....
 and aromatic hydrocarbon
Aromatic hydrocarbon

An aromatic hydrocarbon or arene is a hydrocarbon, of which the molecular structure incorporates one or more planar sets of six carbon atoms that are connected by delocalised electrons numbering the same as if they consisted of alternating single and double covalent bonds....
s. Coal tar is among the by-products when coal
Coal

Coal is a readily combustion black or brownish-black sedimentary rock. The harder forms, such as anthracite, can be regarded as metamorphic rock because of later exposure to elevated temperature and pressure....
 is carbonized
Carbonization

Carbonization or Carbonisation is the term for the conversion of an organic substance into carbon or a carbon-containing residue through pyrolysis or destructive distillation....
 to make coke
Coke (fuel)

Cokes are the solid carbonaceous material derived from destructive distillation of low-ash, low-sulfur bituminous coal. Cokes from coal are grey, hard, and porous....
 or gasified to make coal gas
Coal gas

Coal gas is a flammable gaseous fuel made from coal and supplied to the user via a piped distribution system. Town gas is a more general term referring to manufactured gaseous fuels produced for sale to consumers and municipalities....
. Coal tars are complex and variable mixtures of phenols
Phenols

In organic chemistry, phenols, sometimes called phenolics, are a class of chemical compounds consisting of a hydroxyl Functional group attached to an aromatic hydrocarbon group....
, polycyclic aromatic hydrocarbon
Polycyclic aromatic hydrocarbon

Polycyclic aromatic hydrocarbons are chemical compounds that consist of fused aromatic simple aromatic ring and do not contain heteroatoms or carry substituents....
s (PAHs), and heterocyclic compound
Heterocyclic compound

Heterocyclic compounds are organic compounds containing at least one atom of carbon, and at least one element other than carbon, such as sulfur, oxygen or nitrogen within a ring structure....
s.

g flammable, coal tar is sometimes used for heating or to fire boiler
Boiler

A boiler is a closed Pressure vessel in which water or other fluid is heated. The heated or vaporized fluid exits the boiler for use in various processes or heating applications....
s. Like most heavy oils, it must be heated before it will flow easily.

It can be used in medicated shampoo
Shampoo

Shampoo is a hair care product used for the removal of sebum, dirt, skin particles, dandruff, environmental pollutants and other contaminant particles that gradually build up in hair....
, soap
SOAP

SOAP, originally defined as Simple Object Access Protocol, is a protocol specification for exchanging structured information in the implementation of Web Services in computer networks....
 and ointment
Ointment

An ointment is a viscous semisolid preparation used topically on a variety of body surfaces. These include the skin and the mucus membranes of the eye , vagina, anus, and nose....
, as a treatment for dandruff
Dandruff

Dandruff is due to the excessive shedding of dead skin cells from the scalp. As it is normal for skin cell s to die and flake off, a small amount of flaking is normal and in fact quite common....
 and psoriasis
Psoriasis

Psoriasis is a chronic, non-contagious autoimmune disease which affects the skin and joints. It commonly causes red scaly patches to appear on the skin....
, as well as being used to kill and repel head lice.






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Encyclopedia


Coal tar is a brown or black liquid of high viscosity
Viscosity

Viscosity is a measure of the Drag of a fluid which is being deformed by either shear stress or extensional stress. In everyday terms , viscosity is "thickness"....
, which smells of naphthalene
Naphthalene

Naphthalene, also known as naphthalin, naphthaline, tar camphor, white tar, albocarbon, or antimite and not to be confused with naphtha, is a crystalline, Aromaticity, white, solid hydrocarbon with formula Carbon10hydrogen8 and the structure of two fused benzene rings....
 and aromatic hydrocarbon
Aromatic hydrocarbon

An aromatic hydrocarbon or arene is a hydrocarbon, of which the molecular structure incorporates one or more planar sets of six carbon atoms that are connected by delocalised electrons numbering the same as if they consisted of alternating single and double covalent bonds....
s. Coal tar is among the by-products when coal
Coal

Coal is a readily combustion black or brownish-black sedimentary rock. The harder forms, such as anthracite, can be regarded as metamorphic rock because of later exposure to elevated temperature and pressure....
 is carbonized
Carbonization

Carbonization or Carbonisation is the term for the conversion of an organic substance into carbon or a carbon-containing residue through pyrolysis or destructive distillation....
 to make coke
Coke (fuel)

Cokes are the solid carbonaceous material derived from destructive distillation of low-ash, low-sulfur bituminous coal. Cokes from coal are grey, hard, and porous....
 or gasified to make coal gas
Coal gas

Coal gas is a flammable gaseous fuel made from coal and supplied to the user via a piped distribution system. Town gas is a more general term referring to manufactured gaseous fuels produced for sale to consumers and municipalities....
. Coal tars are complex and variable mixtures of phenols
Phenols

In organic chemistry, phenols, sometimes called phenolics, are a class of chemical compounds consisting of a hydroxyl Functional group attached to an aromatic hydrocarbon group....
, polycyclic aromatic hydrocarbon
Polycyclic aromatic hydrocarbon

Polycyclic aromatic hydrocarbons are chemical compounds that consist of fused aromatic simple aromatic ring and do not contain heteroatoms or carry substituents....
s (PAHs), and heterocyclic compound
Heterocyclic compound

Heterocyclic compounds are organic compounds containing at least one atom of carbon, and at least one element other than carbon, such as sulfur, oxygen or nitrogen within a ring structure....
s.

Applications

Being flammable, coal tar is sometimes used for heating or to fire boiler
Boiler

A boiler is a closed Pressure vessel in which water or other fluid is heated. The heated or vaporized fluid exits the boiler for use in various processes or heating applications....
s. Like most heavy oils, it must be heated before it will flow easily.

It can be used in medicated shampoo
Shampoo

Shampoo is a hair care product used for the removal of sebum, dirt, skin particles, dandruff, environmental pollutants and other contaminant particles that gradually build up in hair....
, soap
SOAP

SOAP, originally defined as Simple Object Access Protocol, is a protocol specification for exchanging structured information in the implementation of Web Services in computer networks....
 and ointment
Ointment

An ointment is a viscous semisolid preparation used topically on a variety of body surfaces. These include the skin and the mucus membranes of the eye , vagina, anus, and nose....
, as a treatment for dandruff
Dandruff

Dandruff is due to the excessive shedding of dead skin cells from the scalp. As it is normal for skin cell s to die and flake off, a small amount of flaking is normal and in fact quite common....
 and psoriasis
Psoriasis

Psoriasis is a chronic, non-contagious autoimmune disease which affects the skin and joints. It commonly causes red scaly patches to appear on the skin....
, as well as being used to kill and repel head lice. When used as a medication in the U.S.
United States

The United States of America is a Federal government constitutional republic comprising U.S. state and a federal district. The country is situated mostly in central North America, where its Contiguous United States and Washington, D.C., the Capital districts and territories, lie between the Pacific Ocean and Atlantic Oceans, Borders of the U...
, coal tar preparations are considered an OTC (over-the-counter drug
Over-the-counter drug

Over-the-counter drugs are medications that may be sold to a customer without a medical prescription. The term "over-the-counter" is somewhat counter-intuitive, since these items can often be found on the shelves of stores and bought like any other packaged product in some countries in contrast to prescription drug which are more likely to l...
) pharmaceutical and are subject to regulation by the United States Food and Drug Administration. Name brands include Denorex, Balnetar, Psoriasin, Tegrin, T-Gel
T-Gel

T-Gel is a medicated shampoo produced by Neutrogena. It reduces psoriasis, dandruff, seborrheic dermatitis, and Dihydrotestosterone levels. It has a limited antiandrogen effect, and is used by some people to slow hair loss....
, and Neutar. Coal tar is also used to synthesize acetaminophen, or Tylenol. Coal tar was formerly used as one of the primary ingredients of asphalt pavements. 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, parking lots and walkways.

Tar
Tar

Tar is modified resin produced from the wood and roots of pine by destructive distillation under pyrolysis. It is a viscosity black liquid. Production and trade in tar was a major contributor in the economies of Northern Europe and Colonial America....
 is used in treatment of the skin disease psoriasis
Psoriasis

Psoriasis is a chronic, non-contagious autoimmune disease which affects the skin and joints. It commonly causes red scaly patches to appear on the skin....
, where coal tar is the most effective. Petroleum tar was also used in ancient Egypt
Ancient Egypt

Ancient Egypt was an Ancient history civilization in eastern North Africa, concentrated along the lower reaches of the Nile in what is now the modern nation of Egypt....
ian mummification
Mummy

A mummy is a corpse whose skin and organs have been preserved by either intentional or incidental exposure to chemicals, extreme coldness, very high humidity, or lack of air when bodies are submerged in bogs....
 circa 1000 BC.

Tar was a vital component of the first sealed, or "tarmac
Tarmac

Tarmac is a type of pavement , pioneered by John Loudon McAdam in around 1820. Strictly speaking, Tarmac refers to a material patented by Edgar Purnell Hooley in 1901....
", roads. The streets of Baghdad
Baghdad

Baghdad is the Capital of Iraq and of Baghdad Governorate, with which it is also coterminous. With a municipal population estimated at 6.5 million, it is the largest city in Iraq, and the second largest city in the Arab World....
 were the first to be paved with tar from the 8th century AD.

Safety

According to the International Agency for Research on Cancer
International Agency for Research on Cancer

The International Agency for Research on Cancer is an intergovernmental agency forming part of the World Health Organisation of the United Nations....
, preparations that include more than 5 percent of crude coal tar are Group 1
List of IARC Group 1 carcinogens

Substances, mixtures and exposure circumstances in this list have been classified by the International Agency for Research on Cancer as Group 1: The agent is carcinogenic to humans....
 carcinogen
Carcinogen

The term carcinogen refers to any substance, radionuclide or radiation that is an agent directly involved in the promotion of cancer or in the increase of its propagation....
.

According to the National Psoriasis Foundation
National Psoriasis Foundation

The National Psoriasis Foundation is the United States? leading patient-driven, nonprofit advocacy organization that serves the estimated 7.5 million Americans affected by psoriasis and psoriatic arthritis....
 and the FDA, coal tar is a valuable, safe and inexpensive treatment option for millions of people with psoriasis and other scalp conditions. Coal tar concentrations between 0.5% and 5% are safe and effective for psoriasis, and no scientific evidence suggests that the coal tar in the concentrations seen in non-prescription treatments is carcinogenic. The NPF states that coal tar contains approximately 10,000 different chemicals, of which only about 50% have been identified , and the composition of coal tar varies with its origin and type of coal (eg: lignite
Lignite

Lignite, often referred to as brown coal, or Rosebud coal by Northern Pacific Railroad,is a soft brown fuel with characteristics that put it somewhere between coal and peat....
, bituminous
Bituminous coal

Bituminous coal is a relatively soft coal containing a tarlike substance called bitumen. It is of higher quality than lignite but poorer quality than Anthracite....
 or anthracite) used to make it.

See also

  • Creosote
    Creosote

    Creosote is the name used for a variety of products including wood creosote and coal tar creosote. Wood creosote is created by high temperature treatment of beech and other woods, or from the resin of the Creosote bush....
  • Cresolene
    Cresolene

    Cresolene is a dark liquid with a pungent smell made from coal tar used in the 19th and early 20th century as a disinfectant and to treat various ailments such as colds and measles....
  • Preservative
    Preservative

    A preservative is a natural or synthetic chemical compound that is added to products such as foods, pharmaceuticals, paints, biological samples, wood, etc....
  • Tar
    Tar

    Tar is modified resin produced from the wood and roots of pine by destructive distillation under pyrolysis. It is a viscosity black liquid. Production and trade in tar was a major contributor in the economies of Northern Europe and Colonial America....


External links