Fluoride

1. What are fluorides?

• 1.1 Which fluorides are most relevant?
• 1.2 What are fluorides used for in industry?

1.1 Which fluorides are most relevant?

Fluorine (F) is an element of the halogen family, which also includes chlorine, bromine and iodine. It forms inorganic and organic compounds called fluorides. Living organisms are mainly exposed to inorganic fluorides through food and water. Based on quantities released and concentrations present naturally in the environment as well as the effects on living organisms, the most relevant inorganic fluorides are hydrogen fluoride (HF), calcium fluoride (CaF₂), sodium fluoride (NaF), sulfur hexafluoride (SF₆) and silicofluorides. They are the focus of this Digest. More...

1.2 What are fluorides used for in industry?

Fluorides are important industrial chemicals with a number of uses but the largest uses are for aluminium production, drinking water fluoridation and the manufacture of fluoridated dental preparations.

• Hydrogen fluoride (HF) is a colourless, pungent liquid or gas that is highly soluble in organic solvents (e.g., benzene) and in water. It is mainly used in the production of synthetic cryolite (Na₃AlF₆), aluminium fluoride (AlF₃), motor gasoline alkylates and chlorofluorocarbons (CFCs). It is also used in etching semiconductor devices, cleaning and etching glass, cleaning brick and aluminium and tanning leather, as well as in removing rust.
• Calcium fluoride (CaF₂) is a colourless solid that is relatively insoluble in water and dilute acids and bases. It is used to produce steel, glass and enamel (because it lowers the melting temperature), hydrofluoric acid and anhydrous hydrogen fluoride (as raw material), and aluminium (as electrolyte).
• Sodium fluoride (NaF) is a colourless to white solid that is moderately soluble in water. It is used in the fluoridation of drinking water and in the manufacture of dental preparations such as toothpaste. It is also used in the production of steel and aluminium (to lower the melting temperature), glass and enamel, or as an insecticide and a preservative (for glues and wood).
• Sulfur hexafluoride (SF₆) is a colourless, odourless, inert gas that is slightly soluble in water and readily soluble in ethanol and bases. It is used extensively in various electronic components and in the production of magnesium and aluminium.
• Silicofluorides such as fluorosilicic acid (H₂SiF₆) and sodium hexafluorosilicate (Na₂SiF₆) are also used for the fluoridation of drinking water supplies

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