| Dihydrogen hexafluorosilicate | |
|---|---|
| IUPAC name | Dihydrogen hexafluorosilicate |
| Other names | Hexafluorosilicic acid fluorosilicic acid fluosilicic acid, silicofluoride |
| Identifiers | |
| CAS number | 16961-83-4 |
| RTECS number | VV8225000 |
| Properties | |
| Molecular formula | H2F6Si |
| Molar mass | 144.0922 g/mol |
| Appearance | colourless solution |
| Density | 1.22 g/cm3 25% aqueous soln |
| Structure | |
| Molecular shape | Octahedral SiF62− |
| Hazards | |
| MSDS | External MSDS |
| Main hazards | Toxic, corrosive. |
| R-phrases | R20, Plantilla:R21, Plantilla:R22, Plantilla:R34, Plantilla:R41 |
| S-phrases | Plantilla:S26, Plantilla:S27 |
| Flash point | Non-flammable. |
| Related compounds | |
| Related compounds | HF HPF6 HBF4 |
| Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa) Infobox references | |
Hexafluorosilicic acid is the chemical compound with the formula H2SiF6. The free acid is encountered as an equilibrium mixture with hexaflurorosilicate anion (SiF62−) only in solution in solvents that are proton donors[1] at low pH. In aqueous solution, evaporation of H2SiF6 results in loss of HF and SiF4.
H2SiF6 is a by-product from the reaction of fluoroapatite with sulfuric acid, which produces HF, which in turn reacts with silicate minerals:
- SiO2 + 6 HF → H2SiF6 + 2 H2O
Aqueous solutions of H2SiF6 contain the hexafluorosilicate anion, SiF62−. In this octahedral anion, the Si-F bond distances are 1.71 Å.[2]
Uses[]
H2SiF6 is commonly used for water fluoridation in several countries including the United States, Great Britain, and Ireland.
H2SiF6 is a reagent in organic synthesis for cleaving Si-O bonds of silyl ethers. It is more reactive for this purpose than HF. It reacts faster with t-butyldimethysilyl (TBDMS) ethers than triisopropylsilyl (TIPS) ethers.[3]
Hexafluorosilicic acid and the salts are used as wood preservation agents. The aluminium and magnesium hexafluorosilicate are two used compounds. [4]
Safety[]
Hexafluorosilicic acid releases hydrogen fluoride when evaporated, so it has similar risks. It is corrosive and may cause fluoride poisoning; inhalation of the vapors may cause lung edema. Like hydrogen fluoride, it attacks glass and stoneware.[5]
References[]
- ↑ J. P. Nicholson (2005). "Electrodeposition of Silicon from Nonaqueous Solvents". J. Electrochem. Soc. 152 (12): C795-C802. DOI:10.1149/1.2083227.
- ↑ Holleman, A. F.; Wiberg, E. "Inorganic Chemistry" Academic Press: San Diego, 2001. ISBN 0-12-352651-5.
- ↑ Pilcher, A. S.; DeShong, P. “Fluorosilicic Acid” in Encyclopedia of Reagents for Organic Synthesis, Copyright © 2001 John Wiley & Sons. DOI: 10.1002/047084289X.rf013
- ↑ Carsten Mai, Holger Militz (2004). "Modification of wood with silicon compounds. inorganic silicon compounds and sol-gel systems: a review". Wood Science and Technology 37 (5). DOI:10.1007/s00226-003-0205-5.
- ↑ Hexafluorosilicic acid Chemical Safety Card http://www.cdc.gov/niosh/ipcsneng/neng1233.html
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