Sodium tetrafluoroborate, also called sodium borofluoride, is a compound with formula NaBF₄. It forms colorless water-soluble rhombic crystals and is soluble in water (108 g/100 ml) and less soluble in organic solvents.

It is a source of tetrafluoroborate

Tetrafluoroborate

Tetrafluoroborate is the anion BF4−. This tetrahedral species is isoelectronic with tetrafluoromethane, CF4 and tetrafluoroammonium NF4+, and is valence isoelectronic with many stable and important species including the closely related anion perchlorate, ClO4−...

 anion. It is used in organic chemistry

Organic chemistry

Organic chemistry is a subdiscipline within chemistry involving the scientific study of the structure, properties, composition, reactions, and preparation of carbon-based compounds, hydrocarbons, and their derivatives...

 for fluorination reactions and as a catalyst, and for lab-scale preparation of boron trifluoride

Boron trifluoride

Boron trifluoride is the chemical compound with the formula BF3. This pungent colourless toxic gas forms white fumes in moist air. It is a useful Lewis acid and a versatile building block for other boron compounds.-Structure and bonding:...

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Sodium tetrafluoroborate is used in some fluxes

Flux (metallurgy)

In metallurgy, a flux , is a chemical cleaning agent, flowing agent, or purifying agent. Fluxes may have more than one function at a time...

 used for brazing

Brazing

Brazing is a metal-joining process whereby a filler metal is heated above and distributed between two or more close-fitting parts by capillary action. The filler metal is brought slightly above its melting temperature while protected by a suitable atmosphere, usually a flux...

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Sodium tetrafluoroborate can be prepared by neutralizing tetrafluoroboric acid with sodium carbonate

Sodium carbonate

Sodium carbonate , Na2CO3 is a sodium salt of carbonic acid. It most commonly occurs as a crystalline heptahydrate, which readily effloresces to form a white powder, the monohydrate. Sodium carbonate is domestically well-known for its everyday use as a water softener. It can be extracted from the...

 or sodium hydroxide.

Na₂O + 2 HBF₄ → 2 NaBF₄ + H₂O

NaOH + HBF₄ → NaBF₄ + H₂O

Na₂CO₃ + 2 HBF₄ → 2 NaBF₄ + H₂O + CO₂

Sodium tetrafluoroborate can be used to prepare nitrosonium tetrafluoroborate

Nitrosonium tetrafluoroborate

Nitrosonium tetrafluoroborate, also called nitrosyl tetrafluoroborate, is a chemical compound with the chemical formula NOBF4. This colourless solid finds use in organic synthesis as a nitrosating agent....

, an explosive, by reacting with nitrogen(III) oxide.

On heating, sodium tetrafluoroborate decomposes to sodium fluoride

Sodium fluoride

Sodium fluoride is an inorganic chemical compound with the formula NaF. A colorless solid, it is a source of the fluoride ion in diverse applications. Sodium fluoride is less expensive and less hygroscopic than the related salt potassium fluoride....

 and boron trifluoride

Boron trifluoride

Boron trifluoride is the chemical compound with the formula BF3. This pungent colourless toxic gas forms white fumes in moist air. It is a useful Lewis acid and a versatile building block for other boron compounds.-Structure and bonding:...

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Sodium tetrafluoroborate can be used for synthesis of ionic liquid

Ionic liquid

An ionic liquid is a salt in the liquid state. In some contexts, the term has been restricted to salts whose melting point is below some arbitrary temperature, such as . While ordinary liquids such as water and gasoline are predominantly made of electrically neutral molecules, ILs are largely made...

s, where the tetrafluoroborate often plays the role of the product's anion.