TRICHLOROETHYLENE

a colourless, somewhat toxic, volatile liquid belonging to the family of organic halogen compounds, nonflammable under ordinary conditions and used as a solvent in dry cleaning, in degreasing of metal objects, and in extraction processes, such as removal of caffeine from coffee or of fats and waxes from cotton and wool. Trichloroethylene was first prepared in 1864; its commercial manufacture, begun in Europe in 1908, is based on the reaction of 1,1,2,2-tetrachloroethane with dilute caustic alkali. The compound is denser than water, in which it is practically insoluble. Trichloroethylene has been used as a cement for polystyrene plastics, especially in model-building kits. Inhalation of the vapours (glue-sniffing) induces euphoria; the practice can be addictive. Industrially, an important use for trichloroethylene is in the manufacture of tetrachloroethylene: trichloroethylene is treated with chlorine to form pentachloroethane, which is converted to tetrachloroethylene by reaction with caustic alkali or by heating in the presence of a catalyst.