Smithson Tennant was born on November 30, 1761 – died on February 22, 1815. Tennant is best known for his discovery of the elements iridium and osmium. The mineral tennantite is named after him.

1. Article on Smithson Tennant – discoverer
of iridium & osmium elements
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2. Biography
 Smithson Tennant was born on November 30, 1761 –
died on February 22, 1815.
 Tennant is best known for his discovery of the
elements iridium and osmium.
 He also contributed to the proof of the identity of
diamond and charcoal.
 The mineral tennantite is named after him.

3. Contributions
 Following research work done by tenant which leads to
the discovery of osmium and iridium elements.
 Tennant fused the insoluble residue with alkali at high
temperature and dissolved the resulting cooled solid in
water, producing a further black solid and a yellow
solution.
 The yellow solution was probably a basic form of osmium
tetroxide, OsO4. The black solid was further treated with
hydrochloric acid, the solid produced was fused with
caustic soda and further treatment with acid obtained red
crystals.
 These are most likely to have been Na2[IrCl6].nH2O. On
heating these, a white powder of an unknown element was
obtained, which was later identified as iridium element.

4. Facts about Osmium element
 Osmium is a hard, brittle, bluish-white transition metal
in the platinum group. Its alloys with platinum, iridium
and other platinum group metals are employed in
fountain pen nibs, electrical contacts, and other
applications.
 Osmium is a hard but brittle metal that remains lustrous
even at high temperatures. It has a very low
compressibility.
 The most common oxidation states of osmium element
include +2, +3, +4, and +8. It can be dissolved by fused
alkalies, especially if an oxidizing agent such as sodium
chlorate is present. Osmium will react at 200° C with air
or oxygen to form OsO4. Osmium has high reflectivity in
the ultraviolet range of the electromagnetic spectrum.

5. Chemical properties of Osmium
 AppearanceBlue - Gray or Blue-Black Metal
 Atomic Number - 76
 Atomic Weight - 190.23 g/mol
 Boiling Point - 5012 °C
 CAS Number - 7440-04-2
 Density - 22.59
 Melting Point - 3033 °C
 Find here Complete osmium chemical properties

6. Facts about iridium element
 Iridium is a very hard, brittle, silvery-white transition metal of
the platinum family. It is the only metal to maintain good
mechanical properties in air at temperatures above 1600 °C.
 The most important iridium compounds in use are the salts
and acids it forms with chlorine, though iridium also forms a
number of organometallic compounds used in industrial
catalysis, and in research.
 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.
 Iridium radioisotopes are used in some radioisotope
thermoelectric generators.

7. Facts about iridium element Cont…
 Iridium forms compounds in oxidation states
between −3 and +9. Iridium has two naturally
occurring, stable isotopes, 191Ir and 193Ir, with
natural abundances of 37.3% and 62.7%,
respectively.
 Iridium is one of the nine least abundant stable
elements in Earth's crust, having an average mass
fraction of 0.001 ppm in crustal rock. Iridium is
obtained commercially as a by-product from nickel
and copper mining and processing.

8. Chemical properties of Iridium
 Appearance - Silver-White Metallic Solid
 Atomic Number – 77
 Atomic Weight - 192.217 g/mol
 Boiling Point - 4428 °C
 CAS Number - 7439-88-5
 Melting Point - 2466 °C
 Find here complete Iridium chemical properties

9. References
 http://www.worldofchemicals.com/462/chemistry-articles/
smithson-tennant-discoverer-of-iridium-osmium-
elements.html
 Iridium Chemical suppliers
 Osmium chemical suppliers
 osmium chemical properties
 Iridium chemical properties