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Osmium ( Os )

Material Information

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General Description:  

Osmium was discovered in 1803 by Smithson Tennant in London, England.

Osmium is a member of the platinum group of metals and is commonly found in conjunction with these elements (abundancy is 1 x 10 4 ppm in the earth's crust). The mixed metals can be extracted from the ore with aqua regia, followed by treatment of the soluble and insoluble portions in various ways. Osmium is found in both portions and is removed as the volatile tetroxide, which can then be reduced. Pure osmium is silver in color and is the densest of all metals. It has a pungent smell, due to the formation of osmium tetroxide

Applications for osmium include its use as an alloying constituent with other group metals, the resultant alloys being extremely hard (e.g. osmiridium, a naturally occuring alloy of osmium and iridium which is extremely hard and is used for the tips of pen nibs). Osmium can also be used as a powerful catalyst in gas reactions.

   

Atomic Properties

Atomic number 76
Atomic radius - Goldschmidt ( nm ) 0.135
Atomic weight ( amu ) 190.2
Crystal structure Hexagonal close packed
Electronic structure Xe 4f14 5d6 6s2
Ionization potential No. eV
1 8.7
2 16
Natural isotope distribution Mass No. %
184 0.02
186 1.58
187 1.6
188 13.3
189 16.1
190 26.4
192 41.0
Photo-electric work function ( eV ) 4.8
Thermal neutron absorption cross-section ( Barns ) 15.3
Valences shown 0, 1, 2, 3, 4, 5, 6, 7, 8

Electrical Properties

Electrical resistivity @20C ( µOhmcm ) 8.8
Temperature coefficient @0-100C ( K-1 ) 0.0041
Superconductivity critical temperature ( K ) 0.66

Mechanical Properties

Material condition Soft Hard Polycrystalline
Bulk modulus ( GPa )     373
Hardness - Vickers 300-350 670-1000
Poisson's ratio     0.25
Tensile modulus ( GPa )     559

Physical Properties

Boiling point ( C ) 5027
Density @20C ( g cm-3 ) 22.5
Melting point ( C ) 3045

Thermal Properties

Coefficient of thermal expansion @0-100C ( x10-6 K-1 ) 4.57
Latent heat of evaporation ( J g-1 ) 3305
Latent heat of fusion ( J g-1 ) 154
Specific heat @25C ( J K-1 kg-1 ) 131
Thermal conductivity @0-100C ( W m-1 K-1 ) 87.6
All information and technical data are given as a guide only. Although every effort has been made to ensure that the information is correct, no warranty is given as to its completeness or accuracy.

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