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Sodium fluoride
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Sodium fluoride is the chemical compound with the formula NaF. This colourless solid is the main source of the fluoride ion in diverse applications. Sodium fluoride is less expensive and less hygroscopic than potassium fluoride.
The mineral form of NaF, villiaumite, is moderately rare. It is known from plutonic nepheline syenite rocks.
um fluoride is an ionic compound, dissolving to give separated Na+ and F− ions.

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Encyclopedia
Sodium fluoride is the chemical compound with the formula NaF. This colourless solid is the main source of the fluoride ion in diverse applications. Sodium fluoride is less expensive and less hygroscopic than potassium fluoride.
The mineral form of NaF, villiaumite, is moderately rare. It is known from plutonic nepheline syenite rocks.
Structure and General properties
Sodium fluoride is an ionic compound, dissolving to give separated Na+ and F− ions. It crystallizes in the cubic (sodium chloride) motif where both Na+ and F− occupy octahedral coordination sites.
Production
NaF is prepared by neutralizing waste hydrofluoric acid resulting from the production of superphosphate fertilizer. It is also generated by treating sodium hydroxide and sodium carbonate with hydrofluoric acid, followed by concentrating the resulting solutions, sometimes with the addition of alcohols to precipitate the NaF:
- HF + NaOH ? NaF + H2O
From solutions containing HF, sodium fluoride precipitates as the bifluoride salt NaHF2. Heating the latter releases HF and gives NaF.
- HF + NaF NaHF2
In a 1986 report, the annual, worldwide consumption of NaF was estimated to be several million tonnes.
Applications
Fluoride salts are used to enhance the strength of teeth by the formation of fluorapatite, a naturally occurring component of tooth enamel. In the US, sodium fluoride was once used to fluoridate drinking water but this has been displaced by hexafluorosilicic acid (H2SiF6) or the related sodium salt (Na2SiF6). Toothpaste often contains sodium fluoride to prevent cavities.
Alternatively, sodium fluoride is used as a cleaning agent, often to remove iron stains. A variety of specialty chemical applications exist in synthesis and extractive metallurgy. The fluoride is the reagent for the synthesis of fluorocarbons. Representative substrates include electrophilic chlorides including acyl chlorides, sulfur chlorides, and phosphorus chloride. Like other fluorides, sodium fluoride finds use in desilylation in organic synthesis.
In medical imaging, fluorine-18-labelled sodium fluoride is used in positron emission tomography (PET). Relative to conventional bone scintigraphy carried out with gamma cameras or SPECT systems, PET offers more sensitivity and spatial resolution. A disadvantage of PET is that fluorine-18 labelled sodium fluoride is less widely available than conventional technetium-99m-labelled radiopharmaceuticals.
Sodium fluoride is used to conserve tissue samples in biochemistry and medicinal testing as fluoride ions stop glycolysis by inhibiting the enzyme enolase. Sodium fluoride is often used together with iodoacetic acid, which inhibits the enzyme aldolase.
Safety
Sodium fluoride is classed as toxic by both inhalation (of dusts or aerosols) and ingestion. In high enough doses, it has been shown to affect the heart and circulatory system, and the lethal dose for a 70 kg human is estimated at 5–10 g.
See also
External links
- at Scorecard, the pollution information site
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