Fluorine is a chemical element with the symbol F

Production

Elemental fluorine and virtually all fluorine compounds are produced from hydrogen fluoride or its aqueous solutions, hydrofluoric acid. Hydrogen fluoride is produced in kilns by the endothermic reaction of fluorite (CaF₂) with sulfuric acid:
CaF₂ + H₂SO₄ → 2 HF(g) + CaSO₄
The gaseous HF can then be absorbed in water or liquefied.
About 20% of manufactured HF is a byproduct of fertilizer production, which produces hexafluorosilicic acid (H₂SiF₆), which can be degraded to release HF thermally and by hydrolysis:
H₂SiF₆ → 2 HF + SiF₄
SiF₄ + 2 H₂O → 4 HF + SiO₂

Industrial routes to F₂

Moissan's method is used to produce industrial quantities of fluorine, via the electrolysis of a potassium fluoride/hydrogen fluoride mixture: hydrogen and fluoride ions are reduced and oxidized at a steel container cathode and a carbon block anode, under 8–12 volts, to generate hydrogen and fluorine gas respectively. Temperatures are elevated, KF•2HF melting at 70 °C (158 °F) and being electrolyzed at 70–130 °C (158–266 °F). KF, which acts to provide electrical conductivity, is essential since pure HF cannot be electrolyzed because it is virtually non-conductive. Fluorine can be stored in steel cylinders that have passivated interiors, at temperatures below 200 °C (392 °F); otherwise nickel can be used Regulator valves and pipework are made of nickel, the latter possibly using Monel instead.^] Frequent passivation, along with the strict exclusion of water and greases, must be undertaken. In the laboratory, glassware may carry fluorine gas under low pressure and anhydrous conditions; some sources instead recommend nickel-Monel-PTFE systems.

Laboratory routes

While preparing for a 1986 conference to celebrate the centennial of Moissan's achievement, Karl O. Christe reasoned that chemical fluorine generation should be feasible since some metal fluoride anions have no stable neutral counterparts; their acidification potentially triggers oxidation instead. He devised a method which evolves fluorine at high yield and atmospheric pressure:
2 KMnO₄ + 2 KF + 10 HF + 3 H2O2 → 2 K₂MnF₆ + 8 H2O + 3 O2↑
2 K₂MnF₆ + 4 SbF₅ → 4 KSbF₆ + 2 MnF₃ + F₂↑
Christe later commented that the reactants "had been known for more than 100 years and even Moissan could have come up with this scheme. As late as 2008, some references still asserted that fluorine was too reactive for any chemical isolation.