1886

Isolation of Fluorine

Joseph-Louis Gay-Lussac (1778–1850), André-Marie Ampère (1775–1836), Humphry Davy (1778–1829), Louis-Jacques Thénard (1777–1857), Ferdinand-Frédéric-Henri Moissan (1852–1907)

If any element in the periodic table can be said to have a personality, fluorine is the one. Unfortunately, that personality is like Lord Byron’s, “mad, bad, and dangerous to know.” Fluorine is by far the most electronegative element and is thus a spectacular oxidizing agent, wildly reactive with any material that can somehow donate electrons. The chemists who attempted to isolate it paid dearly for that knowledge.

In 1810, French physicist André-Marie Ampère was the first to suggest that hydrofluoric acid contained an unknown element, and English chemist Sir Humphry Davy proposed the name fluorine and set out to isolate it. The problem was that both fluorine and gaseous hydrogen fluoride (a constant presence in these experiments) are horribly dangerous, and Davy was among the first to be poisoned, in 1812, surviving with lung and eye damage. Despite his cautionary report, fluorine was enough of a prize that others risked their lives in experiments to isolate it. Inhalation of hydrogen fluoride gas injured French chemists Joseph-Louis Gay-Lussac and Louis-Jacques Thénard, and the Knox brothers, George and Thomas. Some years later, Belgian chemist Paulin Louyet and French chemist Jerome Nicklés were killed by fumes, and English chemist George Gore nearly died in a violent explosion.

French chemist Ferdinand-Frédéric-Henri Moissan finally isolated fluorine in 1886, without blowing anything up or being killed. For his apparatus he used electrolysis (as had Gore), with stoppers made out of the mineral fluorite (the Knox brothers’ innovation), all inside a chemically resistant but ferociously expensive vessel made of platinum and iridium and cooled to −58 degrees Fahrenheit (−50 degrees Celsius). Moissan went on to perform the first controlled experiments on fluorine’s reactivity—not surprisingly, he found that many things burst into flame or exploded outright.

Fluorine’s unique properties make it valuable in everything from drugs to cookware, but even today, relatively few chemists encounter it in its elemental form. Special equipment and attention to detail are needed, as fluorine cannot be approached casually.

This 1891 illustration shows Moissan isolating fluorine (explosions, fires, and deadly corrosive vapors not shown).