Fluorine

Fluorine is so reactive that its isolation defeated chemists for most of a century and injured or killed several who tried; it was finally obtained in 1886 by the French chemist Henri Moissan, by low-temperature electrolysis of hydrogen fluoride, work for which he received the Nobel Prize in 1906. Its name comes from fluorspar, the mineral fluorite, from the Latin fluere, to flow, because the mineral was used as a flux to make ores melt and flow more freely. Fluorine is a pale yellow gas, the most electronegative and aggressive of all elements. Despite its danger in the free state, fluorine's compounds pervade modern life: the fluoride added to toothpaste and drinking water to strengthen teeth, the non-stick polymer PTFE, and the refrigerants, propellants and etching gases of industry all depend on the element.

Fluoridation of public water supplies, adopted widely in the mid twentieth century to reduce tooth decay, also became one of the most durable targets of American conspiracy theory: from the 1950s onward, groups including the John Birch Society claimed it was a communist plot to poison or control the population, a fear later satirised in the film Dr. Strangelove and one that persists in various forms among fringe health movements today. The episode makes fluorine's most everyday compound a genuine case study in how a public-health measure can acquire an entirely unfounded esoteric mythology of its own.

Fluorine has no mythology, but it has a grim human legend of its own: the so-called fluorine martyrs, the chemists who were poisoned, maimed or killed in the long effort to isolate it. Among them were Humphry Davy, who was injured, the Knox brothers of Ireland, and the Belgian Paulin Louviers and Frenchman Jerome Nickles, whose deaths were attributed to hydrogen fluoride exposure. This history of danger, culminating in Moissan's eventual and cautious success, is the element's true narrative content, standing in for the alchemical or planetary associations that a substance discovered so late simply never acquired.

Andre-Marie Ampere had suspected as early as 1810 that hydrofluoric acid concealed an unknown element akin to chlorine, so the eventual isolation in 1886 closed a gap that had stood open for three quarters of a century. Moissan succeeded only by working at minus 50 degrees Celsius in an apparatus of platinum and iridium, metals resistant enough to survive the gas's ferocity, and even then colleagues initially doubted his results until they were repeated before witnesses. His Nobel Prize, awarded in 1906, cited both the isolation of fluorine and his invention of the electric arc furnace, but he did not live to enjoy the honour long, dying the following year.