osmious

Os"mi*ous, a. (Chem.) Defn: Denoting those compounds of osmium in which the element has a valence relatively lower than in the osmic compounds; as, osmious chloride. [Written also osmous.] Osmious acid (Chem.), an acid derived from osmium, analogous to sulphurous acid, and forming unstable salts. It is a brown amorphous substance.

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