A disc of highly enriched uranium processed at the Y-12 National Security Complex at Oak Ridge, Tennessee
21 April 2023
Uranium, chemical symbol U and atomic number 92, is a silvery-gray, radioactive metal. It is the heaviest of the naturally occurring elements. Uranium-238 is the most common isotope, comprising 99% of the uranium found on earth. Uranium-235, obtained through processing U-238, is highly fissionable and can sustain a nuclear chain reaction. Hence it is used in power plants and nuclear weapons.
Uranium was discovered in 1789 by chemist Martin Klaproth in pitchblende. Klaproth originally dubbed it uranit, or uranite in English, after the newly discovered planet Uranus:
Bis zur etwanigen Auffindung eines noch ſchicklichern, lege ich ihr den Namen Uranit bey; welchem Namen ich, nach dem Beyspiel der alten Philosophen, von einem Planeten, nehmlich von dem jungstentdeckten, dem Uranus, entlehne,
(Until I find something even more suitable, I will give it the name uranite, which I borrow after the example of the ancient philosophers from a planet, specifically from the most recently discovered one, Uranus.)
By the following year, Klaproth had amended the name to uranium to conform to the usual nomenclature of metals. But it was later revealed that Klaproth had not actually obtained pure uranium, and what he discovered was in fact uranium oxide. The first chemist to obtain metallic uranium was Eugène Melchior Peligot in 1841. Still, Klaproth is generally credited with the discovery of the element.
In later use, into the present day, uranite (also uraninite) has been used to refer to various ores containing uranium, such as pitchblende.
The name pitchblende is a borrowing from the German Pechblende, so called because of its black color, like pitch or tar. The German word is a compound of Pech (pitch) + blenden (to deceive) and appears by 1720.
Pitchblende is the raw ore, straight out of the ground. After initial processing to remove the other substances, leaving mainly uranium oxide, the lightly processed ore takes on a yellow color and is commonly referred to as yellowcake. That term dates to at least 1949.
Sources:
Klaproth, Martin Heinrich. “Chemische Untersuchung des Uranits, einer neuentdeckten metallischen Substanz. Chemische.” Annalen Für Die Freunde Der Naturlehre, Arzneygelahrtheit, Haushaltungskunst Und Manufacturen, 1789, 2:387–403 at 400. Münchener Digitalisierungs Zentrum Digitale Bibliothek.
Miśkowiec, Pawel. “Name Game: The Naming History of the Chemical Elements—Part 1.” Foundations of Chemistry, 1 November 2022.
Oxford English Dictionary, third edition, March 2012, s.v. uranium, n., uranite, n.; June, 2006, pitchblend, n.; January 2018, yellowcake, n.
Photo credit: US Department of Energy, 1996(?). Wikimedia Commons. Public domain image.