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Rhodium and Iridium – Comparison – Properties

This article contains comparison of key thermal and atomic properties of rhodium and iridium, two comparable chemical elements from the periodic table. It also contains basic descriptions and applications of both elements. Rhodium vs Iridium.

rhodium and iridium - comparison

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Rhodium and Iridium – About Elements


Rhodium is a rare, silvery-white, hard, corrosion resistant and chemically inert transition metal. It is a noble metal and a member of the platinum group.


Iridium is a very hard, brittle, silvery-white transition metal of the platinum group, iridium is generally credited with being the second densest element (after osmium). It is also the most corrosion-resistant metal, even at temperatures as high as 2000 °C.

Rhodium in Periodic Table

Iridium in Periodic Table

Source: www.luciteria.com

Rhodium and Iridium – Applications


The element’s major use (approximately 80% of world rhodium production) is as one of the catalysts in the three-way catalytic converters in automobiles. Because rhodium metal is inert against corrosion and most aggressive chemicals, and because of its rarity, rhodium is usually alloyed with platinum or palladium and applied in high-temperature and corrosion-resistive coatings. In nuclear reactors, rhodium-based detectors are often used for incore neutron flux measuring.


Iridium is mainly consumed by the automotive, electronic, and chemical industries. Iridium metal is employed when high corrosion resistance at high temperatures is needed, as in high-performance spark plugs, crucibles for recrystallization of semiconductors at high temperatures, and electrodes for the production of chlorine in the chloralkali process. The demand for iridium surged from 2.5 tonnes in 2009 to 10.4 tonnes in 2010, mostly because of electronics-related applications that saw a rise from 0.2 to 6 tonnes – iridium crucibles are commonly used for growing large high-quality single crystals, demand for which has increased sharply.

Rhodium and Iridium – Comparison in Table

Element Rhodium Iridium
Density 12.45 g/cm3 22.65 g/cm3
Ultimate Tensile Strength 950 MPa 2000 MPa
Yield Strength N/A N/A
Young’s Modulus of Elasticity 380 GPa 528 GPa
Mohs Scale 6 6.25
Brinell Hardness 1100 MPa 1670 MPa
Vickers Hardness 1246 MPa 1760 MPa
Melting Point 1964 °C 2410 °C
Boiling Point 3695 °C 4130 °C
Thermal Conductivity 150 W/mK 150 W/mK
Thermal Expansion Coefficient 8.2 µm/mK 6.4 µm/mK
Specific Heat 0.242 J/g K 0.13 J/g K
Heat of Fusion 21.5 kJ/mol 26.1 kJ/mol
Heat of Vaporization 493 kJ/mol 604 kJ/mol