All about Fluorine

It is so reactive that glass, metals, and even water, as well as other substances, burn with a bright flame in a jet of fluorine gas. It is far too reactive to be found in elemental form and has such an affinity for most elements, including silicon, that it can neither be prepared nor be kept in ordinary glass vessels. Instead, it must be kept in specialized quartz tubes lined with a very thin layer of fluorocarbons. In moist air it reacts with water to form also-dangerous hydrofluoric acid.

In aqueous solution, fluorine commonly occurs as the fluoride ion F−, although HF is such a weak acid that substantial amounts of it are present in any water solution of fluoride at near neutral pH. Other forms are fluoro-complexes, such as [FeF4]−, or H2F+.

Fluorides are compounds that combine fluorine with some positively charged counterpart. They often consist of crystalline ionic salts. Fluorine compounds with metals are among the most stable of salts.

Elemental fluorine is prepared industrially by Moissan's original process: electrolysis of anhydrous HF in which KHF2 has been dissolved to provide enough ions for conduction to take place.

In 1986, preparing for a conference to celebrate the 100th anniversary of the discovery of fluorine, Karl Christe discovered a purely-chemical preparation by reacting together at 150 °C solutions in anhydrous HF of K2MnF6 and of SbF5. The reaction is: 2K2MnF6 + 4SbF5 → 4KSbF6 + MnF2 + F2 This is not a practical synthesis, but demonstrates that electrolysis is not essential.