1. A bluish-white, hard metallic element, found in small amounts in osmiridium, nickel, and platinum ores. it is used as a platinum hardener and in making pen points, phonograph needles, and instrument pivots. atomic number 76; atomic weight 190.2; melting point 3,000°C; boiling point 5,000°C; specific gravity 22.57; valence 2, 3, 4, 8. see table at element.

1. a heavy metallic chemical element (symbol os) with an atomic number of 76

1. 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.

1. chemical symbol, os; atomic weight, 191. one of the metals of the platina group.
2. this, the most refractory of the metals, has, though with difficulty, been completely fused into globules by means of the electric furnace.

1. a hard brittle blue-grey or blue-black metallic element that is one of the platinum metals; the heaviest metal known