Sulfur hexafluoride
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Names | |||
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IUPAC name
Sulfur hexafluoride
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Systematic IUPAC name
Hexafluoro-λ6-sulfane[1] | |||
Other names
Elagas
Esaflon | |||
Identifiers | |||
3D model (
JSmol ) |
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ChEBI | |||
ChemSpider | |||
ECHA InfoCard
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100.018.050 | ||
EC Number |
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2752 | |||
KEGG | |||
MeSH | Sulfur+hexafluoride | ||
PubChem CID
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RTECS number
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UNII | |||
UN number | 1080 | ||
CompTox Dashboard (EPA)
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Properties | |||
SF6 | |||
Molar mass | 146.05 g·mol−1 | ||
Appearance | Colorless gas | ||
Odor | odorless[2] | ||
Density | 6.17 g/L | ||
Melting point | −64 °C; −83 °F; 209 K | ||
Boiling point | −50.8 °C (−59.4 °F; 222.3 K) | ||
Critical point (T, P) | 45.51±0.1 °C, 3.749±0.01 MPa[3] | ||
0.003% (25 °C)[2] | |||
Solubility | slightly soluble in water, very soluble in ethanol, hexane, benzene | ||
Vapor pressure | 2.9 MPa (at 21.1 °C) | ||
−44.0×10−6 cm3/mol | |||
Thermal conductivity
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Viscosity | 15.23 μPa·s[5] | ||
Structure | |||
Orthorhombic, oP28
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Oh | |||
Orthogonal hexagonal | |||
Octahedral | |||
0 D | |||
Thermochemistry | |||
Heat capacity (C)
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0.097 kJ/(mol·K) (constant pressure) | ||
Std molar
entropy (S⦵298) |
292 J·mol−1·K−1[6] | ||
Std enthalpy of (ΔfH⦵298)formation |
−1209 kJ·mol−1[6] | ||
Pharmacology | |||
V08DA05 (WHO) | |||
License data | |||
Hazards | |||
GHS labelling:[7] | |||
Warning | |||
H280 | |||
P403 | |||
NFPA 704 (fire diamond) | |||
NIOSH (US health exposure limits): | |||
PEL (Permissible)
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TWA 1000 ppm (6000 mg/m3)[2] | ||
REL (Recommended)
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TWA 1000 ppm (6000 mg/m3)[2] | ||
IDLH (Immediate danger) |
N.D.[2] | ||
Safety data sheet (SDS) | External MSDS | ||
Related compounds | |||
Related sulfur fluorides
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Disulfur decafluoride | ||
Related compounds
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Selenium hexafluoride Sulfuryl fluoride | ||
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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Sulfur hexafluoride or sulphur hexafluoride (
Typical for a
SF
6 has 23,500 times greater
6 gas contained in its medium- and high-voltage switchgear. Uses in magnesium, aluminium, and electronics manufacturing also hastened atmospheric growth.[9]
Synthesis and reactions
Sulfur hexafluoride on Earth exists primarily as a synthetic industrial gas, but has also been found to occur naturally.[10]
SF
6 can be prepared from the elements through exposure of S
8 to F
2. This was also the method used by the discoverers Henri Moissan and Paul Lebeau in 1901. Some other sulfur fluorides are cogenerated, but these are removed by heating the mixture to disproportionate any S
2F
10 (which is highly toxic) and then scrubbing the product with NaOH to destroy remaining SF
4.
Alternatively, using bromine, sulfur hexafluoride can be synthesized from SF4 and CoF3 at lower temperatures (e.g. 100 °C), as follows:[11]
There is virtually no reaction chemistry for SF
6. A main contribution to the inertness of SF6 is the
6 has an atmospheric lifetime of around 3200 years, and no significant environmental sinks other than the ocean.[14]
Applications
By 2000, the
Dielectric medium
SF
6 is used in the
Gas-insulated electrical gear is also more resistant to the effects of pollution and climate, as well as being more reliable in long-term operation because of its controlled operating environment. Exposure to an arc chemically breaks down SF
6 though most of the decomposition products tend to quickly re-form SF
6, a process termed "self-healing".
SF
6 is also commonly encountered as a high voltage dielectric in the high voltage supplies of particle accelerators, such as Van de Graaff generators and Pelletrons and high voltage transmission electron microscopes.
Alternatives to SF
6 as a dielectric gas include several fluoroketones.
Medical use
SF
6 is used to provide a tamponade or plug of a retinal hole in retinal detachment repair operations[21] in the form of a gas bubble. It is inert in the vitreous chamber.[22] The bubble initially doubles its volume in 36 hours due to oxygen and nitrogen entering it, before being absorbed in the blood in 10–14 days.[23]
SF
6 is used as a contrast agent for
Tracer compound
Sulfur hexafluoride was the
6.
Sulfur hexafluoride was used as a non-toxic test gas in an experiment at St John's Wood tube station in London, United Kingdom on 25 March 2007.[27] The gas was released throughout the station, and monitored as it drifted around. The purpose of the experiment, which had been announced earlier in March by the Secretary of State for Transport Douglas Alexander, was to investigate how toxic gas might spread throughout London Underground stations and buildings during a terrorist attack.
Sulfur hexafluoride is also routinely used as a tracer gas in laboratory fume hood containment testing. The gas is used in the final stage of ASHRAE 110 fume hood qualification. A plume of gas is generated inside of the fume hood and a battery of tests are performed while a gas analyzer arranged outside of the hood samples for SF6 to verify the containment properties of the fume hood.
It has been used successfully as a tracer in oceanography to study diapycnal mixing and air-sea gas exchange.[28]
Other uses
- The
- Insulated glazing windows have used it as a filler to improve their thermal and acoustic insulation performance.[30][31]
- SF
6 plasma is used in the semiconductor industry as an etchant in processes such as deep reactive-ion etching. A small fraction of the SF
6 breaks down in the plasma into sulfur and fluorine, with the fluorine ions performing a chemical reaction with silicon.[32] - Tires filled with it take longer to deflate from diffusion through rubber due to the larger molecule size.[30]
- The United States Navy's Mark 50 torpedo closed Rankine-cycle propulsion system is powered by sulfur hexafluoride in an exothermic reaction with solid lithium.[34]
- Waveguides in high-power microwave systems are pressurized with it. The gas electrically insulates the waveguide, preventing internal arcing.
- Electrostatic loudspeakers have used it because of its high dielectric strength and high molecular weight.[35]
- The feedstock.
- For entertainment purposes, when breathed, SF
6 causes the voice to become significantly deeper, due to its density being so much higher than air. This phenomenon is related to the more well-known effect of breathing low-density helium, which causes someone's voice to become much higher. Both of these effects should only be attempted with caution as these gases displace oxygen that the lungs are attempting to extract from the air. Sulfur hexafluoride is also mildly anesthetic.[36][37] - For science demonstrations / magic as "invisible water" since a light foil boat can be floated in a tank, as will an air-filled balloon.
- It is used for benchmark and calibration measurements in Associative and Dissociative Electron Attachment (DEA) experiments[38][39]
Greenhouse gas
-
Sulfur hexafluoride (SF6) measured by the Advanced Global Atmospheric Gases Experiment (AGAGE) in the lower atmosphere (troposphere) at stations around the world. Abundances are given as pollution free monthly mean mole fractions in parts-per-trillion.
-
Abundance and growth rate of SF
6 in Earth's troposphere (1978-2018).[9] -
Atmospheric concentration of SF6 vs. similar man-made gases (right graph). Note the log scale.
According to the
Measurements of SF6 show that its global average mixing ratio has increased from a steady base of about 54 parts per quadrillion[10] prior to industrialization, to over 11.5 parts per trillion (ppt) as of October 2023, and is increasing by about 0.4 ppt (3.5 percent) per year.[8][42] Average global SF6 concentrations increased by about seven percent per year during the 1980s and 1990s, mostly as the result of its use in magnesium production, and by electrical utilities and electronics manufacturers. Given the small amounts of SF6 released compared to carbon dioxide, its overall individual contribution to global warming is estimated to be less than 0.2 percent,[43] however the collective contribution of it and similar man-made halogenated gases has reached about 10 percent as of 2020.[44] Alternatives are being tested.[45][46]
In Europe, SF
6 falls under the
6 is banned as a tracer gas and in all applications except high-voltage switchgear.[48] It was reported in 2013 that a three-year effort by the United States Department of Energy to identify and fix leaks at its laboratories in the United States such as the Princeton Plasma Physics Laboratory, where the gas is used as a high voltage insulator, had been productive, cutting annual leaks by 1,030 kilograms (2,280 pounds). This was done by comparing purchases with inventory, assuming the difference was leaked, then locating and fixing the leaks.[49]
Physiological effects and precautions
Sulfur hexafluoride is a nontoxic gas, but by displacing oxygen in the lungs, it also carries the risk of asphyxia if too much is inhaled.[50] Since it is more dense than air, a substantial quantity of gas, when released, will settle in low-lying areas and present a significant risk of asphyxiation if the area is entered. That is particularly relevant to its use as an insulator in electrical equipment since workers may be in trenches or pits below equipment containing SF
6.[51]
As with all gases, the density of SF
6 affects the resonance frequencies of the vocal tract, thus changing drastically the vocal sound qualities, or timbre, of those who inhale it. It does not affect the vibrations of the vocal folds. The density of sulfur hexafluoride is relatively high at room temperature and pressure due to the gas's large molar mass. Unlike helium, which has a molar mass of about 4 g/mol and pitches the voice up, SF
6 has a molar mass of about 146 g/mol, and the speed of sound through the gas is about 134 m/s at room temperature, pitching the voice down. For comparison, the molar mass of air, which is about 80% nitrogen and 20% oxygen, is approximately 30 g/mol which leads to a speed of sound of 343 m/s.[52]
Sulfur hexafluoride has an anesthetic potency slightly lower than nitrous oxide;[53] it is classified as a mild anesthetic.[54]
See also
- Selenium hexafluoride
- Tellurium hexafluoride
- Uranium hexafluoride
- Hypervalent molecule
- Halocarbon—another group of major greenhouse gases
- Trifluoromethylsulfur pentafluoride, a similar gas
References
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- ^ a b c d e NIOSH Pocket Guide to Chemical Hazards. "#0576". National Institute for Occupational Safety and Health (NIOSH).
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- ^ ISBN 978-0-618-94690-7.
- ^ GHS: Record of Schwefelhexafluorid in the GESTIS Substance Database of the Institute for Occupational Safety and Health, accessed on 2021-12-13.
- ^ US National Oceanic and Atmospheric Administration. Retrieved 28 December 2023.
- ^ doi:10.5194/acp-20-7271-2020. Material was copied from this source, which is available under a Creative Commons Attribution 4.0 International License.
- ^ doi:10.1029/2000WR900151.)
{{cite journal}}
: CS1 maint: multiple names: authors list (link - ^ Winter RW, Pugh JR, Cook PW (January 9–14, 2011). SF5Cl, SF4 and SF6: Their Bromine−facilitated Production & a New Preparation Method for SF5Br. 20th Winter Fluorine Conference.
- ISBN 978-1429252553.
- ^ Raj G (2010). Advanced Inorganic Chemistry: Volume II (12th ed.). GOEL Publishing House. p. 160. Extract of page 160
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- ^ Jakob F, Perjanik N, Sulfur Hexafluoride, A Unique Dielectric (PDF), Analytical ChemTech International, Inc., archived (PDF) from the original on 2016-03-04
- ^ "Archived copy" (PDF). Archived (PDF) from the original on 2017-10-12. Retrieved 2017-10-12.
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- ^ "SonoVue, INN-sulphur hexafluoride - Annex I - Summary of Product Characteristics" (PDF). European Medicines Agency. Retrieved 2019-02-24.
- ^ C Michael Hogan (September 10, 2011). "Air pollution line source". Encyclopedia of Earth. Archived from the original on 29 May 2013. Retrieved 22 February 2013.
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- ^ Scott C. Bartos (February 2002). "Update on EPA's manesium industry partnership for climate protection" (PDF). US Environmental Protection Agency. Archived from the original (PDF) on October 10, 2012. Retrieved December 14, 2013.
- ^ a b c J. Harnisch and W. Schwarz (2003-02-04). "Final report on the costs and the impact on emissions of potential regulatory framework for reducing emissions of hydrofluorocarbons, perfluorocarbons and sulphur hexafluoride" (PDF). Ecofys GmbH.
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- ^ Y. Tzeng, T.H. Lin (September 1987). "Dry Etching of Silicon Materials in SF
6 Based Plasmas" (PDF). Journal of the Electrochemical Society. Archived from the original (PDF) on 6 April 2012. Retrieved 22 February 2013. - ^ Stanley Holmes (September 24, 2006). "Nike Goes For The Green". Bloomberg Business Week Magazine. Archived from the original on June 3, 2013. Retrieved December 14, 2013.
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- ^ Dick Olsher (October 26, 2009). "Advances in loudspeaker technology - A 50 year prospective". The Absolute Sound. Archived from the original on December 14, 2013. Retrieved December 14, 2013.
- ^ Edmond I Eger MD, et al. (September 10, 1968). "Anesthetic Potencies of Sulfur Hexafluoride, Carbon Tetrafluoride, Chloroform and Ethrane in Dogs: Correlation with the Hydrate and Lipid Theories of Anesthetic Action". Anesthesiology: The Journal of the American Society of Anesthesiologists. 30 (2). Anesthesiology - The Journal of the American Society of Anesthesiologists, Inc: 127–134.
- ^ WTOL (2015-01-27). Sound Like Darth Vader with Sulfur Hexafluoride. YouTube. Imagination Station.
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Further reading
- "Sulfur hexafluoride". Air Liquide Gas Encyclopedia. Archived from the original on 31 March 2012. Retrieved 22 February 2013.
- Christophorou, Loucas G., ISBN 978-0-306-43894-3.
- Holleman AF, Wiberg E (2001). Inorganic Chemistry. San Diego: Academic Press. ISBN 0-12-352651-5.
- Khalifa M (1990). High-Voltage Engineering: Theory and Practice. New York: Marcel Dekker. OCLC 20595838.
- Maller VN, Naidu MS (1981). Advantages in High Voltage Insulation and Arc Interruption in SF6 and Vacuum. Oxford; New York: Pergamon Press. OCLC 7866855.
- SF6 Reduction Partnership for Electric Power Systems
- Matt McGrath (September 13, 2019). "Climate change: Electrical industry's 'dirty secret' boosts warming". BBC News. Retrieved September 14, 2019.