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| Names | |
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| IUPAC name Potassium fluoride | |
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| ChEMBL | |
| ChemSpider | |
| ECHA InfoCard | 100.029.228  |
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PubChem CID | |
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| Properties | |
Chemical formula | KF |
| Molar mass | 58.0967 g/mol (anhydrous) 94.1273 g/mol (dihydrate) |
| Appearance | colourless |
| Density | 2.48 g/cm3 |
| Melting point | 858 °C (1,576 °F; 1,131 K) (anhydrous) 41 °C (dihydrate) 19.3 °C (trihydrate) |
| Boiling point | 1,502 °C (2,736 °F; 1,775 K) |
| anhydrous: 92 g/100 mL (18 °C) 102 g/100 mL (25 °C) dihydrate: 349.3 g/100 mL (18 °C) | |
| Solubility | soluble in HF insoluble in alcohol |
| −23.6·10−6 cm3/mol | |
| Structure | |
Crystal structure | cubic |
| Hazards | |
| GHS pictograms | ) |
| GHS Signal word | Danger |
GHS hazard statements | H301, H311, H331[1] |
GHS precautionary statements | P261, P264, P270, P271, P280, P301+310, P302+352, P304+340, P311, P312, P321, P322, P330, P361, P363, P403+233, P405, P501 |
| NFPA 704 (fire diamond) | |
| Flash point | Non-flammable |
| Lethal dose or concentration (LD, LC): | |
LD50 (median dose) | 245 mg/kg (oral, rat)[2] |
| Related compounds | |
Other anions | Potassium chloride Potassium bromide Potassium iodide |
Other cations | Lithium fluoride Sodium fluoride Rubidium fluoride Caesium fluoride Francium fluoride |
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). | |
Potassium fluoride is the chemical compound with the formula KF. After hydrogen fluoride, KF is the primary source of the fluoride ion for applications in manufacturing and in chemistry. It is an alkali halide and occurs naturally as the rare mineral carobbiite. Solutions of KF will etch glass due to the formation of soluble fluorosilicates, although HF is more effective.
Preparation
Potassium fluoride is prepared by dissolving potassium carbonate in hydrofluoric acid. Evaporation of the solution forms crystals of potassium bifluoride. The bifluoride on heating yields potassium fluoride:
- K2CO3 + 4HF → 2KHF2 + CO2↑ + H2O
- KHF2 → KF + HF↑
Platinum or heat resistant plastic containers are often used for these operations.
Potassium chloride converts to KF upon treatment with hydrogen fluoride. In this way, potassium fluoride is recyclable.[3]
Crystalline properties
KF crystallizes in the cubic NaCl crystal structure. The lattice parameter at room temperature is 0.266 nm.[4]
Applications in organic chemistry
In organic chemistry, KF can be used for the conversion of chlorocarbons into fluorocarbons, via the Finkelstein (alkyl halides)[5] and Halex reactions (aryl chlorides).[3] Such reactions usually employ polar solvents such as dimethyl formamide, ethylene glycol, and dimethyl sulfoxide.[6]
Safety considerations
Like other sources of the fluoride ion, F−, KF is poisonous, although lethal doses approach gram levels for humans. It is harmful by inhalation and ingestion. It is highly corrosive, and skin contact may cause severe burns.
References
- ^ "Potassium Fluoride". sigmaaldrich.com. Retrieved 2018-12-20.
- ^ Chambers, Michael. "ChemIDplus - 7789-23-3 - NROKBHXJSPEDAR-UHFFFAOYSA-M - Potassium fluoride - Similar structures search, synonyms, formulas, resource links, and other chemical information". chem.sis.nlm.nih.gov.
- ^ a b Siegemund, Günter; Schwertfeger, Werner; Feiring, Andrew; Smart, Bruce; Behr, Fred; Vogel, Herward; McKusick, Blaine (2002). "Fluorine Compounds, Organic". Ullmann's Encyclopedia of Industrial Chemistry. Weinheim: Wiley-VCH. doi:10.1002/14356007.a11_349..
- ^ "Potassium fluoride". University College London.
- ^ Vogel, A. I.; Leicester, J.; Macey, W. A. T. (1956). "n-Hexyl Fluoride". Organic Syntheses. 36: 40. doi:10.15227/orgsyn.036.0040.
- ^ Han, Q.; Li, H-Y. "Potassium Fluoride" in Encyclopedia of Reagents for Organic Synthesis, 2001 John Wiley & Sons,New York. doi:10.1002/047084289X.rp214