Sodium monofluorophosphate
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IUPAC name
Disodium phosphorofluoridate
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Other names
Sodium fluorophosphate, disodium monofluorophosphate
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Identifiers | |
3D model (
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ChEBI | |
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ChemSpider | |
ECHA InfoCard
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100.030.381 |
EC Number |
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PubChem CID
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UNII | |
CompTox Dashboard (EPA)
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Properties | |
Na2PFO3 | |
Molar mass | 143.95 g/mol |
Appearance | white powder |
Melting point | 625 °C (1,157 °F; 898 K) |
25 g/100 mL | |
Solubility | insoluble in ethanol, ether |
Pharmacology | |
A01AA02 (WHO) A12CD02 (WHO) | |
Hazards | |
NFPA 704 (fire diamond) | |
Flash point | Non-flammable |
Lethal dose or concentration (LD, LC): | |
LD50 (median dose)
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0,9g/kg (rat, oral) [1] |
Safety data sheet (SDS) | Sigma-Aldrich |
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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Sodium monofluorophosphate, commonly abbreviated SMFP, is an inorganic compound with the chemical formula Na2PO3F. Typical for a salt, MFP is odourless, colourless, and water-soluble. This salt is an ingredient in some toothpastes.[2]
Uses
MFP is best known as an ingredient in some toothpastes.[3] It functions as a source of fluoride via the following hydrolysis reaction:[2]
- PO3F2− + OH− → HPO42− + F−
Fluoride protects tooth enamel from attack by bacteria that cause
MFP is also used in some medications for the treatment of osteoporosis.[2]
In 1991, sodium monofluorophosphate was found by Calgon to inhibit the dissolution of lead in drinking water when used in concentrations between 0.1 mg/L and 500 mg/L.[4]
Tooth decay
Tooth decay is caused by bacteria naturally present in one's mouth. These bacteria form a sticky, colorless soft film on the teeth called plaque. When foods containing carbohydrates (starches and sugars) are eaten, the bacteria that form plaque use the sugar as a form of energy. They also turn it into a glue-like substance that helps them stick to the surface of the tooth. The plaque produces acid, which attacks the enamel.[5]
Chemistry of decay
Tooth enamel consists mostly of calcium hydroxyphosphate, Ca5(PO4)3OH, also known as the mineral hydroxyapatite. Apatite is a hard, insoluble compound. Acid (H+), produced especially after a high-sugar meal, attacks the apatite:
- Ca5(PO4)3OH(s) + H+(aq) → Ca5(PO4)3+(aq) + H2O(ℓ)
Chemistry of enamel fluoridation
The degradation of apatite by loss of OH− causes the enamel to dissolve. The process is reversible as saliva supplies back OH− to reform apatite. If fluoride, F−, ions are present in saliva, fluorapatite, Ca5(PO4)3F, also forms.
- Ca5(PO4)3+(aq) + F−(aq) → Ca5(PO4)3F(s)
Fluorapatite resists attacks by acids better than apatite itself, so the tooth enamel resists decay better than enamel containing no fluoride.[6]
Preparation and structure
Sodium monofluorophosphate is produced industrially by the reaction of sodium fluoride with sodium metaphosphate:[2]
- NaPO3 + NaF → Na2PO3F
The process involves scission of a pyrophosphate bond, analogous to hydrolysis. NaMFP can also be prepared by treating tetrasodium pyrophosphate or disodium phosphate with hydrogen fluoride.[2]
In the laboratory, MFP can be prepared by hydrolysis of difluorophosphate ions with dilute sodium hydroxide:
- PO2F2− + 2 NaOH → Na2PO3F + H2O + F−
Structure
The structure of the fluorophosphate anion consists of
.Discovery and development
Sodium monofluorophosphate was first described in 1929 by the German chemist
Safety
The usual content of MFP in toothpaste is 0.76%. The compound is used in place of sodium fluoride, particularly in children's toothpastes, because it is less acutely toxic, although both have modest toxicities. The LD50 in rats is 0.9 g/kg.[7]
References
- ^ "Safety (MSDS) data for sodium fluorophosphate". Archived from the original on 2009-01-11. Retrieved 2009-07-06.
- ^
- ^ a b Peter Meiers Monofluorophosphate History
- ^ "HealthyTeeth - Healthy Sleep Tips, News and Product Reviews". HealthyTeeth. Retrieved 19 April 2018.
- ^ Davis, R. E., Ph.D., Metcalfe, H. C., Williams, J. E., Castka, J. F. (1999). Modern Chemistry. Austin, TX: Harcourt Brace & Company.
- ^ "Safety (MSDS) data for sodium fluorophosphate". Archived from the original on 2009-01-11. Retrieved 2009-07-06.