Osmic \Os"mic\, a. (Chem.)
   Pertaining to, derived from, or containing, osmium;
   specifically, designating those compounds in which it has a
   valence higher than in other lower compounds; as, osmic
   oxide.
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   Osmic acid. (Chem.)
   (a) Osmic tetroxide. [Obs.]
   (b) Osmic acid proper, an acid analogous to sulphuric acid,
       not known in the free state, but forming a well-known and
       stable series of salts (osmates), which were formerly
       improperly called osmites.

   Osmic tetroxide (Chem.), a white volatile crystalline
      substance, OsO4, the most stable and characteristic of
      the compounds of osmium. It has a burning taste, and gives
      off a vapor, which is a powerful irritant poison,
      violently attacking the eyes, and emitting a strong
      chlorinelike odor. Formerly improperly called osmic
      acid.
      [1913 Webster]

Tetroxide \Tet*rox"ide\, n. [Tetra- + oxide.] (Chem.)
   An oxide having four atoms of oxygen in the molecule; a
   quadroxide; as, osmium tetroxide, OsO4.
   [1913 Webster]