Hydrofluoric acid (hexafluorosilicic acid, hydrogen hexafluorosilicate H 2 [SiF 6 ]) is a strong inorganic acid.
Hydrofluoric Acid | |
|---|---|
Are common | |
| Chem. formula | H₂Si₄F₆ |
Physical properties | |
| condition | - |
| Molar mass | 144.0918 g / mol |
Classification | |
| CAS Number | |
| Pubchem | |
| Chemspider | |
| EINECS Number | 241-034-8 |
| RTECS | VV8225000 |
| UN number | 1778 |
SMILES | |
[H +]. [H +]. F [Si-2] (F) (F) (F) (F) F | |
Inchi | |
1S / F6Si / c1-7 (2,3,4,5) 6 / q-2 / p + 2 | |
Security | |
| Toxicity |  0 3 0 ACID |
| Data is provided for standard conditions (25 ℃, 100 kPa) , unless otherwise indicated. | |
Content
Properties
Hydrofluoric acid exists only in aqueous solution; decomposes in the free form into silicon tetrafluoride SiF 4 and hydrogen fluoride HF. There are solid white crystalline hydrates of hydrofluoric acid with the compositions H 2 [SiF 6 ] * 4H 2 O [ mp = −53 ° C (decomp.)] And H 2 [SiF 6 ] * 2H 2 O ( mp = +19 ° C ), which have the ionic structure (H 5 O 2 + ) 2 * [SiF 6 ] and (H 3 O + ) 2 * [SiF 6 ].
It is stable in a colorless aqueous solution (maximum mass fraction 0.61), distilled without decomposition in the form of a 13.3% solution. It is neutralized by alkalis, ammonia hydrate, reacts with carbonates of alkali, alkaline earth metals and ammonium [1] .
It is a strong acid; when interacting with metal oxides and hydroxides, it forms fluorosilicates .
Acid is toxic and corrosive.
Getting
Hydrofluoric acid is obtained by direct synthesis from the reagents:
It is also obtained by the action of strong acids on sodium hexafluorosilicate, from the gases produced by simple superphosphate.
Application
It is used as a strong disinfectant, but mainly - for the production of salts ( kremneftoridov ). It is also used as a component of solutions for glass etching, for electrolytes in order to obtain electroplating.
Notes
- ↑ R. A. Lidin Chemical properties of inorganic substances
Literature
- Chemical Encyclopedia / Redkol .: Knunyants I.L. et al. - M .: Soviet Encyclopedia, 1990. - T. 2 (Daf-Med). - 671 p. - ISBN 5-82270-035-5 .