Fluorine is an extremely reactive chemical element with atomic number 9
(pictured in liquid form at cryogenic temperatures). A highly toxic pale
yellow gas at standard conditions, it was first described in 1529 as its
principal source fluorite, a mineral added as a flux for smelting, and
named after the Latin verb fluo meaning "flow". As the lightest halogen
and most electronegative element, it is difficult to separate from its
compounds, and several early experimenters died or were injured. The
process employed for its modern production—low-temperature
electrolysis—remains the same as that used by Henri Moissan in 1886 to
achieve its first isolation. The high costs of refining fluorine gas
lead most commercial uses, such as aluminium refining, insulation and
refrigeration, to use its compounds; uranium enrichment is the free
element's largest application. Fluorine is a part of some
pharmaceuticals and appears as the fluoride ion in toothpaste, but has
no known metabolic role in mammals; a few plants possess fluorine-
containing poisons to deter herbivores. Fluorocarbon gases are usually
potent greenhouse gases and organofluorine compounds persist in the
environment.
Read more: <https://en.wikipedia.org/wiki/Fluorine>
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Today's selected anniversaries:
1123:
Pope Calixtus II and Holy Roman Emperor Henry V agreed to the
Concordat of Worms to put an end to the Investiture Controversy.
<https://en.wikipedia.org/wiki/Concordat_of_Worms>
1780:
American Revolutionary War: British officer John André was
captured by Patriot forces, thereby revealing a plot by Continental Army
General Benedict Arnold to hand over West Point, New York.
<https://en.wikipedia.org/wiki/Benedict_Arnold>
1803:
Maratha troops were beaten by British forces at the Battle of
Assaye, one of the decisive battles of the Second Anglo-Maratha War.
<https://en.wikipedia.org/wiki/Battle_of_Assaye>
1868:
Ramón Emeterio Betances led the Grito de Lares, a revolt
against Spanish rule in Puerto Rico.
<https://en.wikipedia.org/wiki/Ram%C3%B3n_Emeterio_Betances>
1932:
The Kingdom of Nejd and Hejaz merged with Al-Hasa and Qatif to
form the Kingdom of Saudi Arabia, with Ibn Saud as the first monarch and
Riyadh as the capital city.
<https://en.wikipedia.org/wiki/Unification_of_Saudi_Arabia>
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Wiktionary's word of the day:
analemma:
An egg-shaped or figure-eight curve that results when the Sun's position
in the sky is plotted out over the year.
<https://en.wiktionary.org/wiki/analemma>
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Wikiquote quote of the day:
God give me strength to face a fact though it slay me.
--Thomas Henry Huxley
<https://en.wikiquote.org/wiki/Thomas_Henry_Huxley>