Fluorine

Fluorine is used to produce over 100 fluorochemicals, including high-temperature plastics.   Hydrofluoric acid, HF, is used to etch glass, e.g., light bulbs.   Fluorochloro hydrocarbons were used in refrigeration and air conditioning, but were phased out because of their harmful environmental effects.   Most fluorine is used in the production of uranium from the hexafluoride, HF₆.   Minute amounts (about 1 part per million) of fluorine are placed in drinking water and toothpaste to prevent tooth cavities. ^{Lide 4-11}

Fluorine is essential to life.   Flourine ions, F^-, maintain tooth and bone strength and growth.   Sources: Fish, tea, most animal foods, fluoridated water.   Humans experience no fluorine deficiencies.  In animal experiments, fluorine deficiency was found to interfere with feeding, growth, and life expectancy.   In large amounts, fluorine is extremely toxic and fluorin compounds are harmful to the environment.

Fluorine compounds were known by the ancients, but because of its extremely high chemical activity, the highest of all the elements, it could not be isolated for a long time.   Georgius Agricola (Georg Bauer), a German physician, described the use of fluorspar, CaF₂, as a "flux" (mixture that promotes the separation of metals from other components in their minerals) in 1529.   In 1670, Schwandhard found that fluorspar treated with acid etched glass.   In 1886, Henri Moisson, a French chemist, finally isolated fluorine by placing a solution of potassium fluoride, KF, in hydrogen fluoride, HF, and passing an electric current through the solution.   The entire experiment had to be conducted in a platinum flask because of the fluorine's high activity.   In addition to fluorspar, CaF₂, fluorine also occurs in the mineral cryolite, Na₂AlF₆, and in many other minerals.  Because fluorine is too reactive to occur in a free state, it is obtained commercially by electrolysis of potassium hydrogen fluoride in anhydrous hydrogen fluoride, similar to the method used by Moisson. ^{Lide 4-11}