The Collaborative International Dictionary of English v.0.48:

Iodine \I"o*dine\ ([imac]"[-o]*d[i^]n or [imac]"[-o]*d[=e]n;
   104), n. [Gr. 'iw`dhs violetlike; 'i`on a violet + e'i^dos
   form: cf. F. iode, iodine. The name was given from the violet
   color of its vapor. See Violet, Idyl.] (Chem.)
   A nonmetallic element, of the halogen group of atomic number
   53, occurring always in combination, as in the iodides. When
   isolated it is in the form of dark gray metallic scales,
   resembling plumbago, soft but brittle, and emitting a
   chlorinelike odor. Symbol I. Atomic weight 126.90. If heated,
   iodine volatilizes in beautiful violet vapors.
   [1913 Webster]

   Note: Iodine was formerly obtained from the ashes of seaweed
         (kelp or varec), but is now also extracted from certain
         natural brines. In the free state, iodine, even in very
         minute quantities, colors starch blue. Iodine and its
         compounds are largely used in medicine (as in
         liniments, antisyphilitics, etc.), in photography, in
         the preparation of aniline dyes, and as an indicator in
         titration.
         [1913 Webster]

   Iodine green, an artificial green dyestuff, consisting of
      an iodine derivative of rosaniline; -- called also night
      green.

   Iodine scarlet, a pigment of an intense scarlet color,
      consisting of mercuric iodide.

   Iodine yellow, a brilliant yellow pigment, consisting of
      plumbic iodide.
      [1913 Webster]