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.
3D model (JSmol)
CompTox Dashboard (EPA)
|Molar mass||58.0967 g/mol (anhydrous) |
94.1273 g/mol (dihydrate)
|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)|
92 g/100 mL (18 °C)
102 g/100 mL (25 °C)
349.3 g/100 mL (18 °C)
|Solubility||soluble in HF |
insoluble in alcohol
|H301, H311, H331|
|P261, P264, P270, P271, P280, P301+P310, P302+P352, P304+P340, P311, P312, P321, P322, P330, P361, P363, P403+P233, P405, P501|
|NFPA 704 (fire diamond)|
|Lethal dose or concentration (LD, LC):|
LD50 (median dose)
|245 mg/kg (oral, rat)|
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
(what is ?)
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:
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.
In organic chemistry, KF can be used for the conversion of chlorocarbons into fluorocarbons, via the Finkelstein (alkyl halides) and Halex reactions (aryl chlorides). Such reactions usually employ polar solvents such as dimethyl formamide, ethylene glycol, and dimethyl sulfoxide. More efficient fluorination of aliphatic halides can be achieved with a combination of crown ether and bulky diols in acetonitrile solvent.
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.