Osmium

Notable characteristics

Osmium in a O₂) is black, non-volatile and much less reactive and toxic.

Due to its very high lanthanide contraction.

Osmium has a very low aggregated diamond nanorods—although there is some debate in the academic community about whether it is in fact this high. A paper by Cynn et al ^[1] reported that osmium had this bulk modulus, based on an experimental result, but other authors have cast doubt upon this (^[2] and references therein).

Osmium metal has the highest oxidation states of osmium are +4 and +3, but oxidation states from +1 to +8 are observed.

Applications

Because of the volatility and extreme toxicity of its oxide, osmium is rarely used in its pure state, and is instead often osmiridium are very hard and, along with other platinum group metals, is almost entirely used in alloys employed in the tips of fountain pens, phonograph needles, instrument pivots, and electrical contacts, as they can resist wear from frequent use.

Osmium tetroxide has been used in fingerprint detection and in staining fatty tissue for microscope slides. As a strong oxidant, it cross-links lipids mainly by reacting with unsaturated carbon-carbon bonds, and thereby both fixes biological membranes in place in tissue samples and simultaneously stains them, since osmium atoms are extremely electron dense, making OsO₄ an important stain for transmission electron microscopy (TEM) studies of many biological materials. An alloy of 90% platinum and 10% osmium (90/10) is used in surgical implants such as pacemakers and replacement pulmonary valves.

The tetroxide (and a related compound, potassium osmate) are important oxidants for chemical synthesis, despite being very poisonous.

In 1898 an Austrian chemist, tungsten (originally known as wolfram). Tungsten has the highest melting point of any metal, and using it in light bulbs increases the luminous efficacy and life of incandescent lamps.

The light bulb manufacturer OSRAM (founded in 1906 when three German companies; Auer-Gesellschaft, AEG and Siemens & Halske combined their lamp production facilities), derived its name from the elements of OSmium and wolfRAM.

History

Osmium (Greek osme meaning "a smell") was discovered in 1803 by William Hyde Wollaston in London, England.

Wollaston and Tennant were looking for a way to purify platinum by aqua regia. Large amounts of insoluble black powder remained as a byproduct of this operation.

Wollaston concentrated on the soluble portion and discovered iridium. Discovery of the new elements was documented in a letter to the Royal Society on June 21, 1804.

Occurrence

Turkey, with 127,000 tons, has the world's largest known reserve of osmium. Bulgaria also has substantial reserves of about 2500 tons. This transition metal is also found in nickel-bearing ores found in the Sudbury, Ontario region with other platinum group metals. Even though the quantity of platinum metals found in these ores is small, the large volume of nickel ores processed makes commercial recovery possible.

Compounds

See also osmium compounds. Osmium tetroxide OsO₄

Isotopes

Main article: isotopes of osmium

Osmium has seven naturally-occurring shocked quartz along the K-T boundary that marks the extinction of the dinosaurs 65 million years ago.

Precautions

Osmium tetroxide is highly volatile, penetrates skin readily, and is very toxic by inhalation, in contact with skin and if swallowed. Airborne low concentrations of osmium vapour can cause lung congestion, skin or eye damage, and it should therefore be used in a fume hood. Osmium tetroxide is rapidly reduced to relatively inert compounds by poly-unsaturated vegetable oils such as corn oil.

References

1. ^ H Cynn, J E Klepeis, C S Yeo and D A Young, "Osmium has the Lowest Experimentally-Determined Compressibility", Phys. Rev. Lett. 88 #13 (2002).
2. ^ B R Sahu and L Kleinman, "Osmium Is Not Harder Than Diamond", Phys. Rev. B 72 (2005)