Hexafluorosilicic acid

"Fluorosilicate" redirects here. For Fluorosilicate glass and glass-ceramics, see Fluorosilicate glass.
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
3D model (JSmol)
ChemSpider
ECHA InfoCard 100.037.289 Edit this at Wikidata
EC Number
  • 241-034-8
RTECS number
  • VV8225000
UNII
UN number 1778
  • InChI=1S/F6Si/c1-7(2,3,4,5)6/q-2/p+2 checkY
    Key: OHORFAFFMDIQRR-UHFFFAOYSA-P checkY
  • InChI=1/F6Si/c1-7(2,3,4,5)6/q-2/p+2
    Key: OHORFAFFMDIQRR-SKRXCDHZAM
  • [H+].[H+].F[Si-2](F)(F)(F)(F)F
  • [H+].[H+].F[Si--](F)(F)(F)(F)F
Properties
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)
miscible
Acidity (pKa) 1.92[1]
1.3465
Structure
Octahedral SiF62−
Hazards
GHS labelling:
GHS05: Corrosive
Danger
H314
P260, P264, P280, P301+P330+P331, P303+P361+P353, P304+P340, P305+P351+P338, P310, P321, P363, P405, P501
NFPA 704 (fire diamond)
NFPA 704 four-colored diamondHealth 3: Short exposure could cause serious temporary or residual injury. E.g. chlorine gasFlammability 0: Will not burn. E.g. waterInstability 0: Normally stable, even under fire exposure conditions, and is not reactive with water. E.g. liquid nitrogenSpecial hazards (white): no code
3
0
0
Flash point Non-flammable
Lethal dose or concentration (LD, LC):
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).
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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.

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