Iridium (Ir)

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Iridium 77Ir192.2

Discovered in 1803 by S. Tennant at London, England.

[Named after the indigo line in its spectrum]

French: iridium
German: iridium
Italian: iridio
Spanish: iridio

Description: Iridium is a hard, lustrous, silvery metal of the so-called platinum group. It is unaffected by air, water, and acids, but dissolves in molten alkali. Iridium is used in special alloys and spark plugs.



Iridium single crystal properties

State: single crystal
Crystal structure: fcc
Production method: Floating zone
Standard size: diameter 8-10mm
thickness 1-2
Orientation: (100), (110) and (111)
Orientation accuracy: <2°, <1°, <0.4° or <0.1°
Polishing: as cut, one or two sides polished
Roughness of surface: <0.03µm
Purity: 99.99%
Typical analysis (ppm): C 3
H < 1
O 9
N < 5
Cu 1.60
Fe 1.80
Ni < 1
Pb 0.30
Si 0.30

Ga, Hf and Ta are below the detection limit

Materials properties

Density: 22.5 g/cm3
Melting point: 2409.85 °C / 2683 °K
Boiling point: 4129.85 °C / 4403 °K
Molar volume: 8.57 cm3
Thermal conductivity: 147 [300 K] Wm-1K-1
Coefficient of linear thermal expansion: 6.4 x 10-6 K-1
Electrical resistivity: 5.3x 10-8 [293 K] Wm
Mass magnetic susceptibility: +1.67 x 10-9(s) kg-1m3
Young's modulus: 528 GPa
Rigidity modulus: 209 GPa
Bulk modulus: 371 GPa
Poisson's ratio: 0.26
Radii: Ir4+ 66; Ir3+ 75; Ir2+ 89; atomic 136; covalent 12
Electronegativity: 2.20 (Pauling); 1.55 (Allred); 5.4 eV (absolute)
Effective nuclear charge: 3.90 (Slater); 10.57 (Clementi); 15.33 (Froese-Fischer)
Number of Isotopes (incl. nuclear isomers): 40
Issotope mass range: 170 -> 198
Crystal structure, (cell dimentions / pm), space group fcc
X-ray diffraction: mass absorption coefficients: CuKα 193 (µ/r) / cm2g-1
MoKα 110 (µ/r) / cm2g-1
Neutron scattering length: 1.06 b/10-12 cm
Thermal neutron capture cross-section: 425 sa / barns


Biological data

Biological role: none
Toxic intake: the pure metal is clinically inet; data on compounds is sparse.
Lethal intake: LD50 (chloride, oral, mouse) = 8.12 mg kg-1
Hazards: Indium chloride is moderately toxic by ingestion, but most compunds are insoluble and not absorbed by the body.
Level in humans  
Blood: n.a., but very low
Bone: n.a.
Liver: n.a.
Muscle: c. 2 x 10-5 p.p.m.
Daily dietary intake: n.a., but very low
Total mass of element in average [70 kg] person: n.a.


Geological data

MineralFormulaDensityHardnessCrystal apperance
Iridium IR 22.4 6 - 6.5 cub., met. white
Iridosmine (Os, Ir) 20 6 - 7 hex., met. white/grey
Osmiridium (Ir, Os) 20 6 - 7 cub., met. white


Chief ore: osmiridium; also found with platinum ores
World production: 3 tonnes/year
Main mining areas: Canada for native element; see also platinum.
Reserves: n.a.
Specimen: available as foil, powder, spronge or wire. Safe.


Sun: 7.1 (relative to H = 1 x 1012)
Earth's crust: 3 x 10-6 p.p.m.
Residence time:  
Oxidation state:  

Source: Emsley, J. (1998) The Elements (3rd Edition)

Overview of elements with access to our shop

1 18
2 13 14 15 16 17
Li Be B C
Na Mg 3 4 5 6 7 8 9 10 11 12 Al Si P S
K Ca Sc Ti V Cr Mn Fe Co Ni Cu Zn Ga Ge As Se
Rb Sr Y Zr Nb Mo
Ru Rh Pd Ag Cd In Sn Sb Te I
Cs Ba La Hf Ta W Re Os Ir Pt Au Hg Tl Pb Bi
Ce Pr Nd
Sm Eu Gd Tb Dy Ho Er Tm Yb Lu

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