Alloys of Osmium

The most important alloy of osmium is osmiridium or iridosmine, which occurs in nature in platinum ores, as has already been mentioned. Two varieties are known, namely, nevyanskite, containing over 40 per cent, of iridium, and siserskite, containing 30 per cent, or less of that metal. Osmiridium is exceptionally resistant to acid attack, and is non-magnetic. It is used in tipping gold pen nibs. No definite compound of osmium and iridium is known, however. In fact osmium does not appear to form compounds with any metals. It dissolves in zinc, and undoubtedly forms an amalgam with mercury, since the last named, in contact with osmium tetroxide, wets glass, containing vessels becoming rapidly silvered. With iron an alloy is formed capable of taking a temper. Osmium, when finely divided, alloys with gold, but the product is attacked by aqua regia. Alloys with copper have been prepared.