The molecular structure of Hexafluorosilicic acid (CAS NO.16961-83-4):

IUPAC Name: Hexafluorosilicon(2-); hydron 
Molecular Weight: 144.091799 g/mol
Molecular Formula: F₆H₂Si 
Density: 1.22 g/mL at 25 °C
Boiling Point: 108-109 °C
Flash Point: 108-109 °C
Storage Temp.: −20 °C
Water Solubility: 1 mg/mL, clear, colorless
Stability: stable in aqueous solution. 
Refractive Index: 1.3500
H-Bond Acceptor: 7
Exact Mass: 143.982996
MonoIsotopic Mass: 143.982996
Canonical SMILES: [H+].[H+].F[Si-2](F)(F)(F)(F)F
InChI: InChI=1S/F6Si/c1-7(2,3,4,5)6/q-2/p+2
InChIKey: OHORFAFFMDIQRR-UHFFFAOYSA-P
EINECS: 241-034-8
Product Categories: Inorganics; Acids; Electronic Chemicals; Micro/Nanoelectronics

 Hexafluorosilicic acid (CAS NO.16961-83-4) is converted to a variety of useful hexafluorosilicate salts. The barium salts is used in the production for phosphors, and potassium salt for porceleins, the magnesium salt for hardened concretes. Hexafluorosilicic acid is also commonly used for water fluoridation in several countries including the United States, Great Britain, and Ireland. Hexafluorosilicic acid is also the feedstock for "virtually all organic and inorganic fluorine-bearing chemicals". The majority of the hexafluorosilicic acid is converted to aluminium fluoride and cryolite which are central to the conversion of aluminium ore into aluminium metal. The conversion to aluminium trifluoride is described as:
H₂SiF₆ + Al₂O₃ → 2 AlF₃ + SiO₂ + H₂O 

 Hexafluorosilicic acid is mainly produced as a by-product from the production of phosphoric acid from apatite and fluorapatite. The net process can be described as
SiO₂ + 6 HF → H₂SiF₆ + 2 H₂O
 Hexafluorosilicic acid can also be produced by treating silicon tetrafluoride and hydrofluoric acid.
Neutralization of solutions of hexafluorosilicic acid with alkali metal bases produces the corresponding alkali metal fluorosilicate salts:
H₂SiF₆ + 2 NaOH → Na₂SiF₆ + 2 H₂O

Reported in EPA TSCA Inventory.

Hazard Codes: C
Risk Statements: 34 
R34:Causes burns.
Safety Statements: 26-36/37/39-45-27 
S26: In case of contact with eyes, rinse immediately with plenty of water and seek medical advice. 
S36/37/39:Wear suitable protective clothing, gloves and eye/face protection. 
S45:In case of accident or if you feel unwell, seek medical advice immediately (show the label whenever possible.) 
S27:Take off immediately all contaminated clothing.
RIDADR: UN 1778 8/PG 2
WGK Germany: 3
RTECS: VV8225000
F: 8-10
Hazard Note: Corrosive
TSCA: Yes
HazardClass: 8
PackingGroup: II
Poison by subcutaneous route. A corrosive irritant to skin, eyes, and mucous membranes. Will react with water or steam to produce toxic and corrosive fumes. When heated to decomposition it emits toxic fumes of F⁻. See also FLUORIDES.

OSHA PEL: TWA 2.5 mg(F)/m³
ACGIH TLV: TWA 2.5 mg(F)/m³; BEI: 3 mg/g creatinine of fluorides in urine prior to shift; 10 mg/g creatinine of fluorides in urine at end of shift.
DOT Classification:  8; Label: Corrosive
NIOSH REL: TWA 2.5 mg(F)/m³

 Hexafluorosilicic acid (CAS NO.16961-83-4) is also named as Acide fluorosilicique ; Acide fluorosilicique [French] ; Acide fluosilicique ; Acide fluosilicique [French] ; Acido fluosilicico ; Acido fluosilicico [Italian] ; CCRIS 2296 ; Caswell No. 463 ; Dihydrogen hexafluorosilicate ; Dihydrogen hexafluorosilicate (2-) ; EPA Pesticide Chemical Code 075305 ; FKS ; Fluorosilicic acid ; Fluosilicic acid ; HSDB 2018 ; Hydrogen hexafluorosilicate ; Hydrosilicofluoric acid ; Kiezelfluorwaterstofzuur ; Kiezelfluorwaterstofzuur [Dutch] ; NSC 16894 ; Sand acid ; Silicate (2-), hexafluoro-, dihydrogen ; Silicofluoric acid ; Silicofluoride ; Silicon hexafluoride dihydride . Hexafluorosilicic acid (CAS NO.16961-83-4) is colourless liquid with a penetrating pungent odor. It is often supplied as a colourless solution in water. It is corrosive to metals and tissue. Both the fumes and very short contact with the liquid can cause severe and painful burns. Hexafluorosilicic acid can soluble in water with release of heat and corrosive fumes. Hexafluorosilicic acid can react with strong acids (such as sulfuric acid) to release fumes of toxic hydrogen fluoride. Attacks glass and materials containing silica. Reacts exothermically with chemical bases (examples: amines, amides, inorganic hydroxides). Reacts with active metals, including iron and aluminum to dissolve the metal and liberate hydrogen and/or toxic gases. It can initiate polymerization in certain alkenes. Flammable and/or toxic gases are also often generated by reactions with dithiocarbamates, isocyanates, mercaptans, nitrides, nitriles, sulfides, and weak or strong reducing agents. Additional gas-generating reactions may occur with sulfites, nitrites, thiosulfates (to give H₂S and SO₃), dithionites (SO₂), and carbonates. It can catalyze (increase the rate of) chemical reactions. Hexafluorosilicic acid decomposes when heated to the boiling point to produce very toxic and corrosive hydrogen fluoride gas. Inhalation of vapor produces severe corrosive effect on mucous membrane. Ingestion causes severe burns of mouth and stomach. Contact with liquid or vapor causes severe burns of eyes and skin.