Hexafluorosilicic acid

Hexafluorosilicic acid
Names
	Preferred IUPAC name Hexafluorosilicic acid
	Systematic IUPAC name Dihydrogen hexafluorosilicate
	Other names Fluorosilicic acid, fluosilic acid, hydrofluorosilicic acid, silicofluoride, silicofluoric acid, oxonium hexafluorosilanediuide, oxonium hexafluoridosilicate(2−)
Identifiers
CAS Number	16961-83-4 ;
3D model (JSmol)	Interactive image; Interactive image;
ChemSpider	17215660 ;
ECHA InfoCard	100.037.289
EC Number	241-034-8;
PubChem CID	21863527;
RTECS number	VV8225000;
UNII	53V4OQG6U1 ;
UN number	1778
CompTox Dashboard (EPA)	DTXSID2029741 ;
	InChI InChI=1S/F6Si/c1-7(2,3,4,5)6/q-2/p+2 Key: OHORFAFFMDIQRR-UHFFFAOYSA-P ; InChI=1/F6Si/c1-7(2,3,4,5)6/q-2/p+2 Key: OHORFAFFMDIQRR-SKRXCDHZAM;
	SMILES [H+].[H+].F[Si-2](F)(F)(F)(F)F; [H+].[H+].F[Si--](F)(F)(F)(F)F;
Properties
Chemical formula	F6H2Si
Molar mass	144.091 g·mol−1
Appearance	transparent, colorless, fuming liquid
Odor	sour, pungent
Density	1.22 g/cm3 (25% soln.); 1.38 g/cm3 (35% soln.); 1.46 g/cm3 (61% soln.)
Melting point	c. 19 °C (66 °F; 292 K) (60–70% solution); < −30 °C (−22 °F; 243 K) (35% solution)
Boiling point	108.5 °C (227.3 °F; 381.6 K) (decomposes)
Solubility in water	miscible
Acidity (pKa)	1.92
Refractive index (nD)	1.3465
Structure
Molecular shape	Octahedral SiF62−
Hazards
	GHS labelling:
Pictograms
Signal word	Danger
Hazard statements	H314
Precautionary statements	P260, P264, P280, P301+P330+P331, P303+P361+P353, P304+P340, P305+P351+P338, P310, P321, P363, P405, P501
NFPA 704 (fire diamond)	3 0 0
Flash point	Non-flammable
	Lethal dose or concentration (LD, LC):
LD50 (median dose)	430 mg/kg (oral, rat)
Safety data sheet (SDS)	External MSDS
Related compounds
Other anions	Hexafluorotitanic acid; Hexafluorozirconic acid
Other cations	Ammonium hexafluorosilicate; Sodium fluorosilicate
Related compounds	Hexafluorophosphoric acid; Fluoroboric 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

Hexafluorosilicic acid is an inorganic compound with the chemical formula H
₂SiF
₆. Aqueous solutions of hexafluorosilicic acid consist of salts of the cation and hexafluorosilicate anion. These salts and their aqueous solutions are colorless.

Hexafluorosilicic acid is produced naturally on a large scale in volcanoes.^[2]^[3] It is manufactured as a coproduct in the production of phosphate fertilizers. The resulting hexafluorosilicic acid is almost exclusively consumed as a precursor to aluminum trifluoride and synthetic cryolite, which are used in aluminium processing. Salts derived from hexafluorosilicic acid are called hexafluorosilicates.

^ Perrin, D. D., ed. (1982) [1969]. Ionisation Constants of Inorganic Acids and Bases in Aqueous Solution. IUPAC Chemical Data (2^nd ed.). Oxford: Pergamon (published 1984). Entry 91. ISBN 0-08-029214-3. LCCN 82-16524.
^ Palache, C., Berman, H., and Frondel, C. (1951) Dana’s System of Mineralogy, Volume II: Halides, Nitrates, Borates, Carbonates, Sulfates, Phosphates, Arsenates, Tungstates, Molybdates, etc. John Wiley and Sons, Inc., New York, 7th edition.
^
Anthony, J.W., Bideaux, R.A., Bladh, K.W., and Nichols, M.C. (1997) Handbook of Mineralogy, Volume III: Halides, Hydroxides, Oxides. Mineral Data Publishing, Tucson.
- Bararite
- Cryptohalite

[P82db-1] Perrin, D. D., ed. (1982) [1969]. Ionisation Constants of Inorganic Acids and Bases in Aqueous Solution. IUPAC Chemical Data (2^nd ed.). Oxford: Pergamon (published 1984). Entry 91. ISBN 0-08-029214-3. LCCN 82-16524.

[Palache-2] Palache, C., Berman, H., and Frondel, C. (1951) Dana’s System of Mineralogy, Volume II: Halides, Nitrates, Borates, Carbonates, Sulfates, Phosphates, Arsenates, Tungstates, Molybdates, etc. John Wiley and Sons, Inc., New York, 7th edition.

[Anthony-3] Anthony, J.W., Bideaux, R.A., Bladh, K.W., and Nichols, M.C. (1997) Handbook of Mineralogy, Volume III: Halides, Hydroxides, Oxides. Mineral Data Publishing, Tucson.
Bararite

Cryptohalite

[4] Bararite

[5] Cryptohalite

[1]

[2]

[3]