Potassium fluoride

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.

Potassium fluoride
Names
IUPAC name
Potassium fluoride
Identifiers
CAS Number
3D model (JSmol)
ChEMBL
ChemSpider
ECHA InfoCard 100.029.228
EC Number
  • 232-151-5
PubChem CID
RTECS number
  • TT0700000
UNII
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)
Solubility in water
 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
Magnetic susceptibility (χ)
 −23.6·10−6 cm3/mol
Structure
Crystal structure
 cubic
Hazards
GHS pictograms
GHS Signal word Danger
GHS hazard statements
 H301, H311, H331[1]
NFPA 704 (fire diamond)
Flammability code 0: Will not burn. E.g. waterHealth code 3: Short exposure could cause serious temporary or residual injury. E.g. chlorine gasReactivity code 0: Normally stable, even under fire exposure conditions, and is not reactive with water. E.g. liquid nitrogenSpecial hazards (white): no code
0
3
0
Flash point Non-flammable
Lethal dose or concentration (LD, LC):
245 mg/kg (oral, rat)[2]
Related compounds
Other anions
 Potassium chloride
Potassium bromide
Potassium iodide
Potassium astatide
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).
N verify (what is YN ?)
Infobox references

Preparation

Potassium fluoride is prepared by dissolving potassium carbonate in excess 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↑

The salt must not be prepared in glass or porcelain vessels as HF and the aqueous solution of KF corrode glass and porcelain. Heat resistant plastic or platinum containers may be used.

Applications in organic chemistry

In organic chemistry, KF can be used for the conversion of chlorocarbons into fluorocarbons, via the Finkelstein reaction.[3] Such reactions usually employ polar solvents such as dimethyl formamide, ethylene glycol, and dimethyl sulfoxide.[4]

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
  1. "Potassium Fluoride". sigmaaldrich.com. Retrieved 2018-12-20.
  2. 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.
  3. Vogel, A. I.; Leicester, J.; Macey, W. A. T. "n-Hexyl Fluoride". Organic Syntheses.CS1 maint: multiple names: authors list (link); Collective Volume, 4, p. 525
  4. 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
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