Potassium fluoride is the

chemical compound A chemical compound is a chemical substance composed of many identical molecules (or molecular entities) containing atoms from more than one chemical element held together by chemical bonds. A molecule consisting of atoms of only one element ...

with the formula KF. After

hydrogen fluoride Hydrogen fluoride (fluorane) is an inorganic compound with the chemical formula . This colorless gas or liquid is the principal industrial source of fluorine, often as an aqueous solution called hydrofluoric acid. It is an important feedstock ...

, KF is the primary source of the

fluoride Fluoride (). According to this source, is a possible pronunciation in British English. is an inorganic, monatomic anion of fluorine, with the chemical formula (also written ), whose salts are typically white or colorless. Fluoride salts ty ...

ion for applications in manufacturing and in chemistry. It is an alkali halide and occurs naturally as the rare

mineral In geology and mineralogy, a mineral or mineral species is, broadly speaking, a solid chemical compound with a fairly well-defined chemical composition and a specific crystal structure that occurs naturally in pure form.John P. Rafferty, ed. (2 ...

carobbiite Carobbiite, chemical formula KF (potassium fluoride), is a rare, soft (Mohs 2 - 2.5), colourless cubic mineral. It is found at Monte Somma, Somma-Vesuvius Complex, Province of Naples, Campania, Italy. It was discovered in 1956 by Italian geologi ...

. 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 Potassium carbonate is the inorganic compound with the formula K2 CO3. It is a white salt, which is soluble in water. It is deliquescent, often appearing as a damp or wet solid. Potassium carbonate is mainly used in the production of soap and gl ...

hydrofluoric acid Hydrofluoric acid is a solution of hydrogen fluoride (HF) in water. Solutions of HF are colourless, acidic and highly corrosive. It is used to make most fluorine-containing compounds; examples include the commonly used pharmaceutical antidepres ...

. Evaporation of the solution forms crystals of

potassium bifluoride Potassium bifluoride is the inorganic compound with the formula . This colourless salt consists of the potassium cation () and the bifluoride anion (). The salt is used as an etchant for glass. Sodium bifluoride is related and is also of commercial ...

. 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.

Crystalline properties

KF crystallizes in the cubic

NaCl Sodium chloride , commonly known as salt (although sea salt also contains other chemical salts), is an ionic compound with the chemical formula NaCl, representing a 1:1 ratio of sodium and chloride ions. With molar masses of 22.99 and 35.45 g/ ...

crystal structure In crystallography, crystal structure is a description of the ordered arrangement of atoms, ions or molecules in a crystalline material. Ordered structures occur from the intrinsic nature of the constituent particles to form symmetric pattern ...

. The lattice parameter at room temperature is 0.266 nm.

Applications in organic chemistry

organic chemistry Organic chemistry is a subdiscipline within chemistry involving the scientific study of the structure, properties, and reactions of organic compounds and organic materials, i.e., matter in its various forms that contain carbon atoms.Clayden, J ...

, KF can be used for the conversion of chlorocarbons into

fluorocarbon Fluorocarbons are chemical compounds with carbon-fluorine bonds. Compounds that contain many C-F bonds often has distinctive properties, e.g., enhanced stability, volatility, and hydrophobicity. Fluorocarbons and their derivatives are commerci ...

s, via the Finkelstein (alkyl halides) and Halex reactions (aryl chlorides).. Such reactions usually employ polar solvents such as dimethyl formamide,

ethylene glycol Ethylene glycol ( IUPAC name: ethane-1,2-diol) is an organic compound (a vicinal diol) with the formula . It is mainly used for two purposes, as a raw material in the manufacture of polyester fibers and for antifreeze formulations. It is an o ...

, and

dimethyl sulfoxide Dimethyl sulfoxide (DMSO) is an organosulfur compound with the formula ( CH3)2. This colorless liquid is the sulfoxide most widely used commercially. It is an important polar aprotic solvent that dissolves both polar and nonpolar compounds a ...

. More efficient fluorination of aliphatic halides can be achieved with a combination of

crown ether In organic chemistry, crown ethers are cyclic chemical compounds that consist of a ring containing several ether groups (). The most common crown ethers are cyclic oligomers of ethylene oxide, the repeating unit being ethyleneoxy, i.e., . Impo ...

and bulky diols in acetonitrile solvent.

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

{{Authority control Potassium compounds Alkali metal fluorides Rock salt crystal structure