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Hydrofluorosilicic acid

Hexafluorosilicic acid
Hexafluorosilicic acid molecular structure.png
Hexafluorosilicic-acid-3D.png
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
EC Number 241-034-8
PubChem CID
RTECS number VV8225000
UN number 1778
Properties
F6H2Si
Molar mass 144.09 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 ca. 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
1.3465
Structure
Octahedral SiF62−
Hazards
Safety data sheet External MSDS
Toxic T – Toxic
Corrosive C – Corrosive
R-phrases (outdated) R34, R25
S-phrases (outdated) (S1/2), S26, S27, S45
NFPA 704
Flammability code 0: Will not burn. E.g., water Health code 3: Short exposure could cause serious temporary or residual injury. E.g., chlorine gas Reactivity code 0: Normally stable, even under fire exposure conditions, and is not reactive with water. E.g., liquid nitrogen Special hazards (white): no codeNFPA 704 four-colored diamond
Flash point Non-flammable
Lethal dose or concentration (LD, LC):
LD50 (median dose)
430 mg/kg (oral, rat)
Related compounds
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).
YesY  (what is YesYN ?)
Infobox references

Sodium fluorosilicate

Hexafluorosilicic acid is an inorganic compound with the chemical formula (H
3
O)
2
SiF
6
(also written as (H
3
O)
2
[SiF
6
]
). It is a colorless liquid rarely encountered undiluted. Hexafluorosilicic acid has a distinctive sour taste and pungent smell. It is produced naturally on a large scale in volcanoes. It is manufactured as a precursor to aluminum trifluoride and synthetic cryolite. It is commonly used as a source of fluoride for water fluoridation. Salts derived from hexafluorosilicic acid are called hexafluorosilicates.

In aqueous solution, the hydronium cation (H3O+) is traditionally equated with a solvated proton, and as such, the formula for this compound is often written as H
2
SiF
6
. Extending that metaphor, the isolated compound is then written as H
2
SiF
6
·2H
2
O
.


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