osmium

n. [ Gr. 'osmh` a smell, odor, akin to 'o`zein to smell. So named in allusion to the strong chlorinelike odor of osmic tetroxide. See Odor. ] (Chem.) A rare metallic element of the platinum group with atomic number 76. It is found native as an alloy in platinum ore, and in iridosmine. It is a hard, infusible, bluish or grayish white metal, and the heaviest substance known. Its tetroxide is used in histological experiments to stain tissues. Symbol Os. Atomic weight 190.2. Specific gravity 22.477. [ 1913 Webster +PJC ]