Silicon tetrafluoride or tetrafluorosilane is a chemical compound with the formula SiF4. This colorless gas is notable for having a narrow liquid range: its boiling point is only 4 °C above its melting point. It was first prepared in 1771 by Carl Wilhelm Scheele by dissolving silica in hydrofluoric acid,[5] and later synthesized by John Davy in 1812.[6] It is a tetrahedral molecule and is corrosive.[7]
Occurrence
Volcanic plumes contain significant amounts of silicon tetrafluoride. Production can reach several tonnes per day.[8] Some amounts are also emitted from spontaneous coal fires.[9] The silicon tetrafluoride is partly hydrolysed and forms hexafluorosilicic acid.
In the laboratory, the compound is prepared by heating barium hexafluorosilicate (Ba[SiF6]) above 300 °C (572 °F) whereupon the solid releases volatile SiF 4, leaving a residue of BaF 2.
Alternatively, sodium hexafluorosilicate (Na2[SiF6]) may also be thermally decomposed at 400 °C (752 °F)—600 °C (1,112 °F) (optionally in inert nitrogen gas atmosphere) [11]: 8
In 2001 it was listed by New Jersey authorities as a hazardous substance that is corrosive and may severely irritate or even burn skin and eyes.[7] It is fatal if inhaled.[3]
^Kruszewski, Ł., Fabiańska, M.J., Ciesielczuk, J., Segit, T., Orłowski, R., Motyliński, R., Moszumańska, I., Kusy, D. 2018 – First multi-tool exploration of a gas-condensate-pyrolysate system from the environment of burning coal mine heaps: An in situ FTIR and laboratory GC and PXRD study based on Upper Silesian materials. Science of the Total Environment, 640-641, 1044-1071; DOI: 10.1016/j.scitotenv.2018.05.319