Fluoroboric acid

Fluoroboric acid
	Hydronium tetrafluoroborate
Hydronium cation	Tetrafluoroborate anion
Names
	Preferred IUPAC name Tetrafluoroboric acid
	Other names Hydrogen tetrafluoroborate; Oxonium tetrafluoroboranuide; Oxonium tetrafluoridoborate(1-); Oxonium tetrafluoroborate;
Identifiers
CAS Number	14219-41-1 ([H3O]+[BF4]−) ; 16872-11-0 (solvent free) ; 80628-99-5 ([H5O2]+[BF4]−) ;
3D model (JSmol)	Interactive image; Interactive image;
ChEBI	CHEBI:38902 ;
ChemSpider	26156 ;
ECHA InfoCard	100.037.165
EC Number	240-898-3;
Gmelin Reference	21702
MeSH	Fluoroboric+acid
PubChem CID	28118;
RTECS number	ED2685000;
UNII	H429WZ9FBQ ;
UN number	1775
CompTox Dashboard (EPA)	DTXSID8029739 ;
	InChI InChI=1S/BF4H/c2-1(3,4)5/h2H Key: YKRRMQXMWYXWJW-UHFFFAOYSA-N ;
	SMILES F[B-](F)(F)[FH+]; [H+].F[B-](F)(F)F;
Properties
Chemical formula	H[BF4]
Molar mass	87.81 g·mol−1
Appearance	Colourless liquid
Density	1.4 g/mL (48% solution in water)
Melting point	−90 °C (−130 °F; 183 K)
Boiling point	130 °C (266 °F; 403 K)
Vapor pressure	5 mmHg (0.67 kPa) (20 °C (68 °F; 293 K))
Acidity (pKa)	~1.8 (MeCN solution)
Hazards
	GHS labelling:
Pictograms
Signal word	Danger
Hazard statements	H314
Precautionary statements	P264, P280, P301+P330+P331, P303+P361+P353, P304+P340+P310, P305+P351+P338+P310, P405, P501
NFPA 704 (fire diamond)	3 1 0
Threshold limit value (TLV)	2.5 mg/m3 (TWA), 6 mg/m3 (STEL)
	NIOSH (US health exposure limits):
PEL (Permissible)	2.5 mg/m3 (TWA)
IDLH (Immediate danger)	250 mg/m3
Related compounds
Related compounds	Hydrogen fluoride; Triflic acid; Hexafluorophosphoric acid;
	Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). verify (what is ?) Infobox references

Fluoroboric acid or tetrafluoroboric acid (archaically, fluoboric acid) is an inorganic compound with the simplified chemical formula H⁺[B F₄]⁻. Solvent-free tetrafluoroboric acid (H[BF₄]) has not been reported. The term "fluoroboric acid" usually refers to a range of compounds including hydronium tetrafluoroborate ([H₃O]⁺[BF₄]⁻), which are available as solutions. The ethyl ether solvate is also commercially available, where the fluoroboric acid can be represented by the formula [H((CH₃CH₂)₂O)_n]⁺[BF₄]⁻, where $n$ is 2.

It is mainly produced as a precursor to other fluoroborate salts. It is a strong acid. Fluoroboric acid is corrosive and attacks the skin. It is available commercially as a solution in water and other solvents such as diethyl ether. It is a strong acid with a weakly coordinating, non-oxidizing conjugate base. It is structurally similar to perchloric acid, but lacks the hazards associated with oxidants.