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

_______________________________ 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

_____________________________ 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

___________________________ 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