Cluster of osmium crystals
24 November 2023
The elements iridium and osmium were discovered together by chemist Smithson Tennant in 1803. Iridium, atomic number 77 and symbol Ir, is a hard, brittle, silvery-white metal. It is the second densest naturally occurring metal. Only osmium, atomic number 76 and symbol Os is denser. That metal is also hard and brittle but bluish-white in color. Both elements are primarily found in platinum ores, and both are rare—osmium is the rarest stable element in the earth’s crust.
At the turn of the nineteenth century, it was discovered that when platinum was dissolved in aqua regia (a mixture of hydrochloric and nitric acid), a black residue resulted. A number of chemists speculated on what the residue might contain, but the amount of residue produced was insufficient for further study. In 1803, chemist Smithson Tennant managed to obtain a larger sample of the residue and discovered it contained the two new elements. The following year he read a paper to the Royal Society of London in which he announced his discovery and named the two metals.
He named one iridium, from the Latin iris (rainbow) + -ium:
As it is necessary to give some name to bodies which have not been known before, and most convenient to indicate by it some characteristic property, I should incline to call this metal Iridium, from the striking variety of colours which it gives, while dissolving in marine acid.
The other he named osmium, from the Greek ὀσμή (osme, odor) +-ium:
When the alkaline solution is first formed, by adding water to the dry alkaline mass in the crucible, a pungent and peculiar smell is immediately perceived. This smell, as I afterwards discovered, arises from the extrication of a very volatile metallic oxide; and, as this smell is one of its most distinguishing characters, I should on that account incline to call the metal Osmium.
Sources:
Miśkowiec, Pawel. “Name Game: The Naming History of the Chemical Elements: Part 2—Turbulent Nineteenth Century.” Foundations of Chemistry, 8 December 2022. DOI: 10.1007/s10698-022-09451-w.
Oxford English Dictionary, second edition, 1989, s.v. iridium, n.; third edition, September 2004, osmium, n.
Tennant, Smithson. “On Two Metals, Found in the Black Powder Remaining after the Solution of Platina” (21 June 1804). Philosophical Transactions of the Royal Society of London, 94, 1804, 411–18 at 414 and 416. JSTOR.
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