The Collaborative International Dictionary of English v.0.48:

Oxymuriatic \Ox`y*mu`ri*at"ic\, a. [Oxy
   (a) + muriatic: cf. F. oxymuriatique.] (Chem.) Pertaining to,
       or consisting of, oxygen and muriatic acid, that is,
       hydrochloric acid. [Archaic.]
       [1913 Webster]

   Oxymuriatic acid, chlorine, formerly so called on the
      supposition that it was a compound of oxygen and muriatic
      acid. [Obs.]
      [1913 Webster]