carbon tetrachloride(redirected from Benziform)
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carbon tetrachloride(tĕ'trəklôr`īd) or
tetrachloromethane(tĕ'trəklôr'əmĕth`ān), CCl4, colorless, poisonous, liquid organic compound that boils at 76.8°C;. It is toxic when absorbed through the skin or when inhaled. It reacts at high temperatures to form the poisonous gas phosgene. Carbon tetrachloride is used in the production of Freon refrigerants, e.g., Freon-12 (dichlorodifluoromethane). Because it is not flammable and is a good solvent for fats, oils, and greases, it is often used commercially for dry cleaning and for degreasing metals. It is sometimes used in fire extinguishers, since its vapors are denser than air and serve to smother a flame. Its use in the home as a spot remover should be avoided because of its poisonous nature.
(also tetrachloromethane), CCl4, a colorless liquid, with a sweetish odor, a melting point of –22.9°C, a boiling point of 76.8°C, and a density of 1.593 g/cm3(at 20°C). Carbon tetrachloride is practically insoluble in water but is soluble in many organic solvents. It forms azeotropic mixtures with water (boiling point 66°C; 95.9 percent CCl4), methanol (55.7°C; 79.4 percent CCl4), and other liquids. It readily dissolves oils, greases, waxes, and many natural and synthetic resins and rubbers. Under ordinary conditions, it is resistant to the action of air, light, and concentrated acids; in the presence of iron or aluminum, it is decomposed by water into CO2 and HCl. It interacts with the alcoholates of the alkali metals to form orthocarbonic-acid esters: CCI4 + 4NaOC2H5 → 4NaCI + C(OC2H5)4; it takes part in the telomerization reaction together with olefins. The chlorine atoms in carbon tetrachloride can be replaced with F, Br, or I. For example, the Freons CCl3F and CCl2F2 are commercially prepared from CCl4 and HF.
Carbon tetrachloride is produced by the chlorination of methane or carbon disulfide, as well as by other methods. It is widely used in various industrial sectors as an incombustible fire-resistant solvent.
Poisoning. Carbon tetrachloride enters the body through the respiratory organs and the skin, inducing a narcotic effect on the central nervous system, a slightly irritating effect on the skin, and a toxic effect on the liver, kidneys, and other organs. Acute poisoning is accompanied by headache, vertigo, weakness, nausea, and vomiting. Severe poisoning cause dyspnea, cyanosis, and an increase in body temperature; strong agitation, loss of consciousness, sense disturbances, and paralysis are possible, as are sometimes toxic emphysema and hepatitis. Chronic poisoning is characterized by gastrointestinal disorders, weight loss, and anemia, as well as by irritation of the eyes and mucosa of the upper respiratory tract. Indications of severe cases are toxic hepatitis, poly-neuritis, and kidney damage. Carbon tetrachloride induces dermatitis on contact with the skin.
Preventive measures include the replacement of carbon tetrachloride with less toxic solvents, prevention of carbon tetrachloride vapors from entering inhaled air, and personal safety measures. Preliminary and periodic medical examinations are also helpful.
A. A. KASPAROV and V. N. FROSIN