Hydrofluorosilicic 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 Y
3D model (JSmol)	Interactive image Interactive image
ChemSpider	17215660 Y
ECHA InfoCard	100.037.289
EC Number	241-034-8
PubChem CID	21863527
RTECS number	VV8225000
UN number	1778
InChI InChI=1S/F6Si/c1-7(2,3,4,5)6/q-2/p+2 Y Key: OHORFAFFMDIQRR-UHFFFAOYSA-P Y 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	144.09 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)
Solubility in water	miscible
Refractive index (nD)	1.3465
Structure
Molecular shape	Octahedral SiF62−
Hazards
Safety data sheet	External MSDS
EU classification (DSD) (outdated)	T – Toxic C – Corrosive
R-phrases (outdated)	R34, R25
S-phrases (outdated)	(S1/2), S26, S27, S45
NFPA 704	0 3 0
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).
Y  (what is YN ?)
Infobox references

Sodium fluorosilicate

Hexafluorosilicic acid is an inorganic compound with the chemical formula (H
3O)
2SiF
6 (also written as (H
3O)
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
2SiF
6. Extending that metaphor, the isolated compound is then written as H
2SiF
6·2H
2O.