COAL TAR n.
A thick, black, tarry liquid, obtained by the distillation of bituminous coal in the manufacture of illuminating gas; used for making printer's ink, black varnish, etc. It is a complex mixture from which many substances have been obtained, especially hydrocarbons of the benzene or aromatic series.
COEFFICIENT n.
e, length, volume, etc.; as, the coefficient of expansion; the coefficient of friction. Arbitrary coefficient (Math.), a literal coefficient placed arbitrarily in an algebraic, expression, the value of the coefficient being afterwards determined by the conditions of the problem.
COKE n.
Mineral coal charred, or depriver of its bitumen, sulphur, or other volatile matter by roasting in a kiln or oven, or by distillation, as in gas works. It is lagerly used where [Written also coak.] Gas coke, the coke formed in gas retorts, as distinguished from that made in ovens.
COLOCYNTH n.
The light spongy pulp of the fruit of the bitter cucumber (Citrullus, or Cucumis, colocynthis), an Asiatic plant allied to the watermelon; coloquintida. It comes in white balls, is intensely bitter, and a powerful cathartic. Called also bitter apple, bitter cucumber, bitter gourd.