\Ba"ri*um\, n. [NL., fr. Gr. bary`s heavy.] (Chem.)
One of the elements, belonging to the alkaline earth group; a
metal having a silver-white color, and melting at a very high
temperature. It is difficult to obtain the pure metal, from
the facility with which it becomes oxidized in the air.
Atomic weight, 137. Symbol, Ba. Its oxide called baryta.
[Rarely written {barytum}.]
Note: Some of the compounds of this element are remarkable
      for their high specific gravity, as the sulphate,
      called heavy spar, and the like. The oxide was called
      barote, by Guyton de Morveau, which name was changed by
      Lavoisier to baryta, whence the name of the metal.