COAL TAR Chemical Properties
- Flash point:
- Dark brown
- Water Solubility
- Not miscible or difficult to mix with water.
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COAL TAR Usage And Synthesis
Coal tars are by-products of the destructive distillation (carbonization) of coal to produce coke or gas. The composition and properties of a coal tar depend primarily on the temperature of the carbonization and to a lesser extent on the nature (source) of the coal used as feedstock. In general, coal tars are complex combinations of hydrocarbons, phenols, and heterocyclic oxygen, sulfur, and nitrogen compounds. Over 400 compounds have been identified in coal tars, and as many as 10,000 may actually be present. The PAH content of coal tars increases with increasing carbonization temperature. Coal tars typically are black or almost-black viscous liquids or semisolids with a characteristic naphthalene-like odor (ATSDR 2002). They are slightly soluble in water, partially soluble in acetone, carbon disulfide, chloroform, diethyl ether, ethanol, methanol, petroleum ether, and sodium hydroxide, and soluble in benzene and nitrobenzene. Lowtemperature coal tars (formed at temperatures below 700°C) are black, viscous liquids that are denser than water and contain a lower percentage (40% to 50%) of aromatic compounds than high-temperature coal tars (IARC 1985). Coal tars are highly flammable and corrosive, and toxic gases may be released when they burn. Their vapors can form explosive mixtures with air (HSDB 2009).
Coal-tar pitches are shiny, dark-brown to black residues produced during the distillation of coal tars. They contain various PAHs, their methyl and polymethyl derivatives, and heteronuclear compounds (IARC 1985).
Coal tars and coal-tar pitches have many uses in industry and in consumer products. Coal tars are used primarily for the production of refined chemicals and coal-tar products, such as creosote, coal-tar pitch, and crude naphthalene and anthracene oils from the distillation of crude coal tar. Coal tar has been used as a fuel in open-hearth furnaces and blast furnaces in the steel industry, as a binder and filler in surface-coating formulations, and as a modifier for epoxy-resin surface coatings. U.S. Pharmacopeia–grade coal tar is approved for use in denatured alcohol (IARC 1985). Coal-tar preparations have been used for many years to treat various skin conditions, such as eczema, psoriasis, seborrheic dermatitis, and dandruff. Both prescription and nonprescription preparations are available and include cleansing bars, creams, gels, lotions, ointments, shampoos, and other topical solutions and suspensions (DermNet NZ 2010). Coal tar is also registered as an active ingredient in pesticides with the U.S. Environmental Protection Agency (EPA 2003).
Coal-tar pitches are used primarily as the binder for aluminumsmelting electrodes (IARC 1984). They are also used in roofing materials, to impregnate and strengthen refractory brick (for lining industrial furnaces), and in surface coatings, such as pipe-coating enamels and black varnishes used as protective coatings for industrial steelwork and as antifouling paints for boats. Hard pitch is used as a binder for foundry cores. Coke-oven pitch is used to produce pitch coke, which is used as the carbon component of electrodes, carbon brushes, and carbon and graphite articles. Distillation fractions and residues from high-temperature coal tars are used for road paving and construction and in the production of naphthalene, recovery of benzene, production of anthracene paste, briquetting of smokeless solid fuel, impregnation of electrodes and fibers, and manufacture of electrodes and graphite (IARC 1985).
A human and experimental skin irritant. A flammable liquid. When heated to SYNS: ANTHMCITE PARTICLES 0 COAL FACINGS 0 COAL, GROUND BITUMINOUS (DOq 0 COAL-MILLED 0 COAL SLAG-MILLED SEA COAL decomposition it emits acrid smoke and irritating fumes.
Coal tars and coal-tar pitches are known to be human carcinogensbased on sufficient evidence of carcinogenicity from studies in humans.
Coast Guard, Department of Homeland Security
Minimum requirements have been established for safe transport of coal-tar pitches on ships and barges.
Department of Transportation (DOT)
Flammable coal-tar distillates are considered a hazardous material, and special requirements have been set for marking, labeling, and transporting these materials.
Environmental Protection Agency (EPA)
Clean Air Act
National Emissions Standards for Hazardous Air Pollutants: Air emissions of hazardous air pollutants from the handling of coal tar are regulated under certain source categories.
Resource Conservation and Recovery Act
Listed Hazardous Waste: Waste codes for which the listing is based wholly or partly on the presence of certain coal-tar residues = K141, K142, K147, K148.
Coal-tar creosote is listed as a hazardous constituent of waste.
Food and Drug Administration (FDA)
Any drug products containing coal tar at levels of 0.5% to 5% must contain a label specifying the identity and concentration of the coal tar.
Any hair dye containing coal tar must display a warning label stating that the product contains an ingredient that has been determined to cause cancer in laboratory animals.
Certain dermal products containing coal tar must provide warning labels of specific precautions for that product.
The use of coal tar in several over-the-counter drugs is no long recognized as safe and effective for the specified uses.
Occupational Safety and Health Administration (OSHA)
While this section accurately identifies OSHA’s legally enforceable PELs for this substance in 2010, specific PELs may not reflect the more current studies and may not adequately protect workers. Permissible exposure limit = 0.2 mg/m3 for coal-tar-pitch volatiles – benzene-soluble fraction.
COAL TAR Preparation Products And Raw materials
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