Iridium is a transition metal with the symbol Ir and atomic number of 77. It was discovered in 1803 by Smithson Tennant in the residue left after dissolving platinum in acids. Iridium is a solid at room temperature, has the highest melting point of any metal, and is mainly used as a hardening agent in platinum alloys and for equipment requiring high heat resistance. It is found naturally with platinum and osmium and recovered as a byproduct of nickel mining.

1. Iridium
Kelsey Taylor
CHE: 120-010
Element Project

2. Basic Information
Symbol: Ir
Atomic mass: 192.22 amu
Transition metal
Atomic number: 77

3. History of Iridium
Discovered in 1803 by Smithson Tennant
(English; Yorkshire, England)
It was found in the residue left behind by
platinum when it dissolved in a mixture of
hydrochloric acid and nitric acid.
The term Iridium comes from the Latin term
“iris” (rainbow) because many of the salts
found within Iridium were brightly colored.

4. Smithson Tennant

5. Properties of Ir
Iridium is a solid at room temperature.
Color: white
Boiling point: 4703 K (4430˚C)
Melting point: 2720 K (2447˚C)
Density: 22.56 g/cm³ (at 293 K)
The most common isotope of Iridium is
193Ir and the most stable are 193Ir and 191Ir

6. Uses of Ir
Iridium is mainly used in platinum alloys as
a hardening agent.
It is also used in making crucibles and
making equipment that is used at high
temperatures, heavy-duty electrical
contacts, and in the tips of pens.
Radioactive isotopes are used in cancer
treatment in radiation therapy.

7. Availability of Ir
Iridium is found with platinum and osmium
in alluvial deposits in many alloys
It is also recovered as a by-product in the
nickel mining industry
Cost: $2300 for 100g in bulk

8. Resources
http://www.chemicool.com/elements/iridiu
m.html
http://www.chemicalelements.com/element
s/ir.html
http://www.facts-about.org.uk/science-
element-iridium.htm