Carbon Tetrachloride, CCl4, is a heavy, nonconducting, nonflammable, colorless liquid.
It yields heavy vapors that have a peculiar odor. Carbon tetrachloride solidifies at −23° C (9.4° F) and boils at 77° C (170.6° F). It specific gravity is 1.585. The carbon tetrachloride molecule is a regular tetrahedron with the carbon atom in the center, and it is nonpolar. The liquid is almost insoluble in water, which is polar, but it dissolves readily in nonpolar solvents, such as alcohol.
Carbon tetrachloride is poisonous. It has a toxicity threshold of about 25 parts per million in air. It apparently can also be absorbed through the skin. Excessive breathing of the vapor or contact with the liquid can cause nausea, and with prolonged exposure, it may lead to liver or kidney damage and finally death.
Carbon tetrachloride is widely used as an industrial solvent and degreasing agent and as an intermediate in the manufacture of other materials. It is also used in grain fumigants and in insecticides. Because carbon tetrachloride is a good solvent for grease it was once widely used in dry-cleaning fluids, but it has now been replaced by less toxic chemicals.
Carbon tetrachloride has been used for extinguishing fires. When heated it liberates large quantities of very heavy vapor that acts to dilute the oxygen in the air and tends to smother the flames. It is a nonconductor of electricity and can be used safely on electrical fires. However, a toxicity hazard results in closed areas from high vapor concentration and from the oxidation of some carbon tetrachloride to phosgene, COCl2, which is a highly poisonous gas.
Carbon tetrachloride is manufactured by heating carbon disulfide with dry chlorine gas in the presence of a catalyst:
|CS2 + 3Cl2 → CCl4 + S2Cl2.|
The products are separated by fractional distillation, and sulfur monochloride is recycled with fresh carbon disulfide to produce additional carbon tetrachloride:
|2S2Cl2 + CS2 → CCl4 + 6S.|