Water Education - Contaminants Facts

Drinking Water Contaminants - Fluoride

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1. General description


Fluoride is a fairly common element that does not occur in the elemental state in nature because of its high reactivity. It accounts for about 0.3 g/kg of the earth's crust and exists in the form of fluorides in a number of minerals, of which fluorspar, cryolite, and fluorapatite are the most common. The oxidation state of the fluoride ion is -1.

PropertySodium fluoride (NaF)Hydrogen fluoride (HF)
Physical stateWhite, crystalline powderColourless liquid or gas with biting smell
Melting point (°C)993-83
Boiling point (°C)1695 at 100 kPa19.5
Density (g/cm3)2.56?
Water solubility42 g/litre at 10 °CReadily soluble below 20 °C
Acidity?Strong acid in liquid form; weak acid dissolved in water

Major uses

Inorganic fluorine compounds are used in aluminum production, as a flux in the steel and glass fiber industries, and in the production of phosphate fertilizers (which contain an average of 3.8% fluorine), bricks, tiles, and ceramics. Fluosilicic acid is used in municipal water fluoridation schemes (1).

Environmental fate

Although sodium fluoride is soluble in water (1), aluminum, calcium, and magnesium fluorides are only sparingly so (3).

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