The Collaborative International Dictionary of English v.0.48:

Chlorine \Chlo"rine\, n. [Gr. ? pale green, greenish yellow. So
   named from its color. See Yellow.] (Chem.)
   One of the elementary substances, commonly isolated as a
   greenish yellow gas, two and one half times as heavy as air,
   of an intensely disagreeable suffocating odor, and
   exceedingly poisonous. It is abundant in nature, the most
   important compound being common salt (Sodium chloride). It is
   powerful oxidizing, bleaching, and disinfecting agent. Symbol
   Cl. Atomic weight, 35.4.
   [1913 Webster]

   Chlorine family, the elements fluorine, chlorine, bromine,
      and iodine, called the halogens, and classed together
      from their common peculiarities.
      [1913 Webster]