Sodium fluoride

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Sodium fluoride
Sodium fluoride
Identifiers
CAS number 7681-49-4 YesY
PubChem 5235
ChemSpider 5045 YesY
UNII 8ZYQ1474W7 YesY
EC number 231-667-8
UN number 1690
KEGG C08142 N
ChEBI CHEBI:28741 YesY
ChEMBL CHEMBL1528 YesY
RTECS number WB0350000
ATC code A01AA01,A12CD01,
V09IX06 (18F)
Properties
Molecular formula NaF
Molar mass 41.988173 g/mol
Appearance White to greenish solid
Odor odorless
Density 2.558 g/cm3
Melting point 993 °C (1,819 °F; 1,266 K)
Boiling point 1,704 °C (3,099 °F; 1,977 K)
Solubility in water 36.4 (0 °C); 40.4 (20 °C); 50.5 (100 °C) g/L[1]
Solubility slightly soluble in HF, ammonia
negligible in alcohol, acetone, SO2, dimethylformamide
Vapor pressure 1 mmHg @ 1077 C°[2]
Refractive index (nD) 1.3252
Thermochemistry
Specific
heat capacity
C
46.82 J/mol K
Std molar
entropy
So298
51.3 J/mol K
Std enthalpy of
formation
ΔfHo298
-573.6 kJ/mol
Gibbs free energy ΔG -543.3 kJ/mol
Hazards
MSDS Sodium fluoride MSDS
EU Index 009-004-00-7
EU classification Toxic T – Toxic
Irritant Xi – Irritant
R-phrases R25, R32, R36/38
S-phrases (S1/2), S22, S36, S45
NFPA 704
Flammability code 0: Will not burn. E.g., water Health code 3: Short exposure could cause serious temporary or residual injury. E.g., chlorine gas Reactivity code 0: Normally stable, even under fire exposure conditions, and is not reactive with water. E.g., liquid nitrogen Special hazards (white): no codeNFPA 704 four-colored diamond
Flash point Non-flammable
LD50 52–200 mg/kg (oral in rats, mice, rabbits)[3]
Related compounds
Other anions Sodium chloride
Sodium bromide
Sodium iodide
Other cations Lithium fluoride
Potassium fluoride
Rubidium fluoride
Caesium fluoride
Related compounds TASF reagent
Except where noted otherwise, data are given for materials in their standard state (at 25 °C (77 °F), 100 kPa)
 N (verify) (what is: YesY/N?)
Infobox references

Sodium fluoride is an inorganic chemical compound with the formula NaF. A colorless solid, it is a source of the fluoride ion in diverse applications. Sodium fluoride is less expensive and less hygroscopic than the related salt potassium fluoride.

Structure, general properties, occurrence[edit]

Sodium fluoride is an ionic compound, dissolving to give separated Na+ and F ions. Like sodium chloride, it crystallizes in a cubic motif where both Na+ and F occupy octahedral coordination sites;[4][5] its lattice spacing, approximately 462 pm, is somewhat smaller than that of sodium chloride.

The mineral form of NaF, villiaumite, is moderately rare. It is known from plutonic nepheline syenite rocks.[6]

Production[edit]

NaF is prepared by neutralizing hydrofluoric acid or hexafluorosilicic acid (H2SiF6), byproducts of the reaction of fluorapatite (Ca5(PO4)3F) (from phosphate rock) from the production of superphosphate fertilizer. Neutralizing agents include sodium hydroxide and sodium carbonate. Alcohols are sometimes used 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.[7]

Applications[edit]

Sodium fluoride is sold in tablets for cavity prevention.

Fluoride salts is often added to drinking water and some food products for dental health. Other fluoride sources are used as well, e.g., salts of hexafluorosilicate. The fluoride enhance the strength of teeth by the formation of fluorapatite, a naturally occurring component of tooth enamel.[8][9] Although sodium fluoride is also used to fluoridate water and, indeed, is the standard by which other water-fluoridation compounds are gauged, hexafluorosilicic acid (H2SiF6) and its salt sodium hexafluorosilicate (Na2SiF6) are more commonly used additives in the U.S.[10] Toothpaste often contains sodium fluoride to prevent cavities.[11]

Sodium fluoride is used as a cleaning agent (e.g., as a "laundry sour").[7]

A variety of specialty chemical applications exist in synthesis and extractive metallurgy. It reacts with electrophilic chlorides including acyl chlorides, sulfur chlorides, and phosphorus chloride.[12] Like other fluorides, sodium fluoride finds use in desilylation in organic synthesis. The fluoride is the reagent for the synthesis of fluorocarbons.[citation needed]

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.[citation needed]

Safety[edit]

The lethal dose for a 70 kg (154 lb) human is estimated at 5–10 g.[7] Sodium fluoride is classed as toxic by both inhalation (of dusts or aerosols) and ingestion.[13] In high enough doses, it has been shown to affect the heart and circulatory system. For occupational exposures, the Occupational Safety and Health Administration and the National Institute for Occupational Safety and Health have established occupational exposure limits at 2.5 mg/m3 over an eight-hour time-weighted average.[14]

In the higher doses used to treat osteoporosis, plain sodium fluoride can cause pain in the legs and incomplete stress fractures when the doses are too high; it also irritates the stomach, sometimes so severely as to cause ulcers. Slow-release and enteric-coated versions of sodium fluoride do not have gastric side effects in any significant way, and have milder and less frequent complications in the bones.[15] In the lower doses used for water fluoridation, the only clear adverse effect is dental fluorosis, which can alter the appearance of children's teeth during tooth development; this is mostly mild and is unlikely to represent any real effect on aesthetic appearance or on public health.[16]

See also[edit]

References[edit]

  1. ^ Haynes, William M., ed. (2011). CRC Handbook of Chemistry and Physics (92nd ed.). CRC Press. p. 5.194. ISBN 1439855110. 
  2. ^ Lewis, R.J. Sax's Dangerous Properties of Industrial Materials. 10th ed. Volumes 1–3 New York, NY: John Wiley & Sons Inc., 1999., p. 3248
  3. ^ Martel, B.; Cassidy, K. (2004), Chemical Risk Analysis: A Practical Handbook, Butterworth–Heinemann, p. 363, ISBN 1-903996-65-1 
  4. ^ Wells, A.F. (1984), Structural Inorganic Chemistry, Oxford: Clarendon Press, ISBN 0-19-855370-6 
  5. ^ "Chemical and physical information" (PDF), Toxicological profile for fluorides, hydrogen fluoride, and fluorine, Agency for Toxic Substances and Disease Registry (ATDSR), September 2003, p. 187, retrieved 2008-11-01 
  6. ^ Mineral Handbook (PDF) (version 1), Mineral Data Publishing, 2005. 
  7. ^ a b c Aigueperse, Jean; Paul Mollard, Didier Devilliers, Marius Chemla, Robert Faron, Renée Romano, Jean Pierre Cuer (2005), "Fluorine Compounds, Inorganic", in Ullmann, Encyclopedia of Industrial Chemistry, Weinheim: Wiley-VCH, doi:10.1002/14356007.a11_307 
  8. ^ Bourne, Geoffrey Howard (1986), Dietary research and guidance in health and disease, Karger, p. 153, ISBN 3-8055-4341-7 , Snippet view from page 153
  9. ^ Klein, Cornelis; Hurlbut, Cornelius Searle; Dana, James Dwight (1999), Manual of Mineralogy (21 ed.), Wiley, ISBN 0-471-31266-5 
  10. ^ Division of Oral Health, National Center for Prevention Services, CDC (1993), Fluoridation census 1992 (PDF), retrieved 2008-12-29. 
  11. ^ "Sodium fluoride, Molecule of the week". American Chemical Society. 2008-02-19. Retrieved 2008-11-01. 
  12. ^ Halpern, D.F. (2001), "Sodium Fluoride", Encyclopedia of Reagents for Organic Synthesis, John Wiley & Sons, doi:10.1002/047084289X.rs071 
  13. ^ NaF MSDS. hazard.com
  14. ^ CDC - NIOSH Pocket Guide to Chemical Hazards
  15. ^ Murray TM, Ste-Marie LG. Prevention and management of osteoporosis: consensus statements from the Scientific Advisory Board of the Osteoporosis Society of Canada. 7. Fluoride therapy for osteoporosis. CMAJ. 1996;155(7):949–54. PMID 8837545.
  16. ^ National Health and Medical Research Council (Australia). A systematic review of the efficacy and safety of fluoridation [PDF]. 2007. ISBN 1-86496-415-4. Summary: Yeung CA. A systematic review of the efficacy and safety of fluoridation. Evid Based Dent. 2008;9(2):39–43. doi:10.1038/sj.ebd.6400578. PMID 18584000. Lay summary: NHMRC, 2007.