Aug 7 2013
Topics Covered
Introduction
Chemical Properties
Physical Properties
Mechanical Properties
Thermal Properties
Applications
Introduction
Osmium is a hard, brittle, bluish-white chemical element in Group 8 of the periodic table, with an atomic number 76. It is the densest of all naturally occuring elements, and it is found in platinum ores as well as iridomine and nickel-bearing ores. It was discovered in 1803 in London, by an English chemist Smithson Tennant.
Powdered osmium in air tends to form pungent, highly toxic osmium tetroxide that causes damage to eye, lung and skin.
Commercially, osmium is recovered as a by-product of nickel refining. It is unworkable as a metal, and hence it has very few applications.
Chemical Properties
The chemical properties of osmium are provided in the table below.
|
Chemical Data |
|
CAS number |
4/2/7440 |
|
Thermal neutron cross section |
15 barns/atom |
|
Electrode potential |
0.70 V |
|
Ionic radius (crystal ionic radius for valence +6) |
0.690 Å |
|
Electronegativity |
2.2 |
|
X-ray absorption edge (K) |
0.1678 Å |
Physical Properties
The following table discusses the physical properties of osmium.
|
Properties |
Metric |
Imperial |
|
Density |
22.5 g/cm3 |
0.813 lb/in3 |
|
Melting point |
3050 °C |
5520°F |
|
Boiling point |
5012°C |
9054°F |
Mechanical Properties
The mechanical properties of osmium are tabulated below.
|
Properties |
Metric |
Imperial |
|
Tensile strength |
1000 MPa |
145000 psi |
|
Poisson’s ratio |
0.25 |
0.25 |
|
Modulus of elasticity |
560 GPa |
81200 ksi |
|
Bulk modulus |
462 GPa |
67007 ksi |
|
Rigidity modulus |
222 GPa |
32198.4 ksi |
|
Hardness, Brinell |
293 |
293 |
|
Hardness, Vickers |
300 |
300 |
|
Hardness, Rockwell A |
66 |
66 |
|
Hardness, Rockwell C |
30 |
30 |
Thermal Properties
The thermal properties of manganese are tabulated below.
|
Properties |
Metric |
Imperial |
|
Thermal expansion co-efficient (@20-100°C/68-212°F) |
6.60 µm/m°C |
3.67 µin/in°F |
|
Thermal conductivity |
91.67 W/mK |
636.2 BTU in/hr.ft².°F |
Applications
Due to volatility and toxicity of its oxide, osmium is rarely used in its pure form for high-wear applications. Its alloys with platinum and iridium are used in fountain pen tips, electrical contacts and instrument pivots.
Osmium tetraoxide has been used in fingerprint detection and staining fatty tissues using electron and optical microscopy.
An alloy of 90% platinum and 10% osmium is used in surgical implants such as pacemakers and replacement heart valves. Finely divided osmium metal is also used as a catalyst.
The high reflectivity of osmium in the UV range is desirable for use in space-based UV spectrometers having reduced mirror sizes due to space limitations.