200Applications
Fluorides are pervasive in modern technology. Hydrofluoric acid is the fluoride synthesized on the
largest scale. It is produced by treating fluoride minerals with sulfuric acid. Hydrofluoric acid and its
anhydrous form hydrogen fluoride are used in the production of fluorocarbons and aluminum
fluorides. Hydrofluoric acid has a variety of specialized applications, including its ability to dissolve
glass.
Inorganic Chemicals
Fluoride salts are used in the manufacture of many inorganic chemicals, many of which contain
fluoride covalently bonded to the metal or nonmetal in question. Some examples of these are:
Cryolite (Na 3 AlF 6 ) is a pesticide that can leave fluoride on agricultural commodities. Cryolite
was originally utilized in the preparation of aluminum.
Sulfuryl fluoride (SO 2 F 2 ) is used as a pesticide and fumigant on agricultural crops. In 2010,
the United States Environmental Protection Agency proposed to withdraw the use of sulfuryl
fluoride on food. Sulfuryl fluoride releases fluoride when metabolized.
Sulfur hexafluoride is an inert, nontoxic insulator gas that is used in electrical transformers
and as a tracer gas in indoor air quality investigations.
Uranium hexafluoride, although not ionic, is prepared from fluoride reagents. It is utilized in
the separation of isotopes of uranium between the fissile isotope U-235 and the non-fissile
isotope U-238 in preparation of nuclear reactor fuel and atomic bombs. This is due to the
volatility of fluorides of uranium.
Organic Chemicals
Fluoride reagents are significant in synthetic organic chemistry. Organofluorine chemistry has
produced many useful compounds over the last 50 years. Included in this area are
polytetrafluorethylene (Teflon), polychlorotrifluoroethylene (moisture barriers), efavirenz
(pharmaceutical used for treatment of HIV), fluoxetine (an antidepressant), 5-fluorouracil (an
anticancer drug), hydrochlorofluorocarbons and hydrofluorcarbons (refrigerants, blowing agents
and propellants).
Due to the affinity of silicon for fluoride, and the ability of silicon to expand its coordination number,
silyl ether protecting groups can be easily removed by the fluoride sources such as sodium fluoride
and tetra-n-butylammonium fluoride (TBAF). This is quite useful for organic synthesis and the
production of fine chemicals. The Si-F linkage is one of the strongest single bonds. In contrast,
other silyl halides are easily hydrolyzed.
Cavity Prevention
Fluoride-containing compounds are used in topical and systemic fluoride therapy for preventing
tooth decay. They are used for water fluoridation and in many products associated with oral
hygiene. Originally, sodium fluoride was used to fluoridate water; hexafluorosilicic acid (H 2 SiF 6 ) and
its salt sodium hexafluorosilicate (Na 2 SiF 6 ) are more commonly used additives, especially in the
United States.
The fluoridation of water is known to prevent tooth decay and is considered by the U.S. Centers for
Disease Control and Prevention as "one of 10 great public health achievements of the 20th
century". In some countries where large, centralized water systems are uncommon, fluoride is
delivered to the populace by fluoridating table salt. Fluoridation of water has its critics (see Water
fluoridation controversy).