Hydrofluoric acid: Difference between revisions

Hydrofluoric acid
Names
	IUPAC name Fluorane
	Other names Fluorhydric acid; Hydronium fluoride
Properties
Chemical formula	HF (aq)
Appearance	Colorless
Density	1.15 g/mL (for 48% soln.)
Acidity (pKa)	3.17
Hazards
	GHS labelling:
Pictograms
Signal word	Danger
Hazard statements	H280, H300, H310, H314, H330
Precautionary statements	P260, P262, P264, P270, P271, P280, P284, P301+P310, P301+P330+P331, P302+P350, P303+P361+P353, P304+P340, P305+P351+P338, P310, P320, P321, P322, P330, P361, P363, P403+P233, P405, P410+P403, P501
NFPA 704 (fire diamond)	4 0 0
	Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). verify (what is ?) Infobox references

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Hydrofluoric acid is a solution of hydrogen fluoride (HF) in water. It is used to make most fluorine-containing compounds; examples include the pharmaceutical fluoxetine (Prozac) and the material PTFE (Teflon). Elemental fluorine is produced from it. Solutions of HF are colourless, acidic and highly corrosive. It is in common use to etch glass and silicon wafers.

When hydrofluoric acid comes into contact with human skin it causes deep burns.

Production

Hydrofluoric acid was first prepared in 1771, by Carl Wilhelm Scheele .^[4] It is now mainly produced by treatment of the mineral fluorite, CaF₂, with concentrated sulfuric acid at ca. 265 °C.

CaF₂ + H₂SO₄ → 2 HF + CaSO₄

The acid is also a by-product of the production of phosphoric acid from apatite/fluoroapatite. Digestion of the mineral with sulfuric acid at elevated temperatures releases a mixture of gases, including hydrogen fluoride, which may be recovered. ^[5]

Because of its high reactivity toward glass, hydrofluoric acid is stored in plastic containers.^[5]^[6]

Hydrofluoric acid can be found in nature, having been released in a volcanic eruption.

Properties

In dilute aquous solution hydrogen fluoride behaves as a weak acid,^[7] Infrared spectroscopy has been used to show that, in solution, dissociation is accompanied by formation of the ion pair H₃O⁺·F⁻.^[8]^[9]

H₂O + 2HF ⇌ H⁺ + F^- + H₃O⁺⋅F^-, pK_a = 3.17

This ion pair has been characterized in the crystalline state at very low temperature.^[10] Further association has been characterized both in solution and in the solid state.^[11]

HF + F^- ⇌ HF₂^- log K = 0.6

It is assumed that polymerization occurs as the concentration increases. This assumption is supported by the isolation of a salt of a tetrameric anion anion H₃F₄^-^[12] and by low-temperature X-ray crystallography.^[10] The species that are present in concentrated aqueous solutions of hydrogen fluoride have not been characterized; the formation of polymeric species, H_n-1F_n^-, is highly likely.

The Hammett acidity function, H₀, for 100% HF is estimated to be between −10.2 and −11.^[13] which is comparable to the value −12 for sulfuric acid.^[14]^[15]

Solutions of hydrofluoric acid attack glass, so they are stored and used in vessels made of teflon. They attack human skin, so must be handled with great care: see #Health and Safety, below.

Uses

Hydrofluoric acid has a variety of uses in industry and research. The principal use is in organofluorine chemistry for the production of Teflon, fluoropolymers, fluorocarbons, and refrigerants such as freon.^[5] Most high-volume inorganic fluoride compounds are prepared from hydrofluoric acid. Foremost are Na₃AlF₆, cryolite, and AlF₃, aluminium trifluoride. Metallic aluminium is produced by electrolysis of a molten mixture of these compounds. The acid is used in the production of uranium hexafluoride.

It is used as an etchant and cleaning agent. In metalworking, hydrofluoric acid is used as a pickling agent to remove oxides and other impurities from stainless and carbon steels because of its limited ability to dissolve steel.^{[citation needed]} It is used in the semiconductor industry as a major component of Wright Etch and buffered oxide etch, which are used to clean silicon wafers.

A 5% to 9% hydrofluoric acid gel is also commonly used to etch all ceramic dental restorations to improve bonding.^[16] For similar reasons, dilute hydrofluoric acid is a component of household rust stain remover, in car washes in "wheel cleaner" compounds, in ceramic and fabric rust inhibitors, and in water spot removers.^[6]^[17] Because of its ability to dissolve iron oxides as well as silica-based contaminants, hydrofluoric acid is used in pre-commissioning boilers that produce high-pressure steam.

Because of its ability to dissolve (most) oxides and silicates, hydrofluoric acid is useful for dissolving rock samples (usually powdered) prior to analysis. In similar manner, this acid is used in acid macerations to extract organic fossils from silicate rocks. Fossiliferous rock may be immersed directly into the acid, or a cellulose nitrate film may be applied (dissolved in amyl acetate), which adheres to the organic component and allows the rock to be dissolved around it.^[18]

Diluted hydrofluoric acid (1 to 3 %wt.) is used in the petroleum industry in a mixture with other acids (HCl or organic acids) in order to stimulate the production of water, oil, and gas wells specifically where sandstone is involved.^{[citation needed]}

Hydrofluoric acid is also used by some collectors of antique glass bottles to remove so-called 'sickness' from the glass, caused by acids (usually from the soil in which the bottle was buried) attacking the soda content of the glass.^{[citation needed]}

Offset printing companies use hydrofluoric acid to remove unwanted images from printing plates. Felt-tip markers called "deletion pens" are available to make the process safer for the worker.^{[citation needed]}

Health and safety

In addition to being a highly corrosive liquid, hydrofluoric acid is also a powerful contact poison. Because of the ability of hydrofluoric acid to penetrate tissue, poisoning can occur readily through exposure of skin or eyes, or when inhaled or swallowed. Symptoms of exposure to hydrofluoric acid may not be immediately evident, and this can provide false reassurance to victims, causing them to delay medical treatment.^[19] Despite having an irritating odor, HF may reach dangerous levels without an obvious odor.^[6] HF interferes with nerve function, meaning that burns may not initially be painful. Accidental exposures can go unnoticed, delaying treatment and increasing the extent and seriousness of the injury.^[19] Symptoms of HF exposure include irritation of the eyes, skin, nose, and throat, eye and skin burns, rhinitis, bronchitis, pulmonary edema (fluid buildup in the lungs), and bone damage.^[20]

Once absorbed into blood through the skin, it reacts with blood calcium and may cause cardiac arrest. Burns with areas larger than 160 cm² (25 square inches) have the potential to cause serious systemic toxicity from interference with blood and tissue calcium levels.^[21] In the body, hydrofluoric acid reacts with the ubiquitous biologically important ions Ca²⁺ and Mg²⁺. Formation of insoluble calcium fluoride is proposed as the etiology for both precipitous fall in serum calcium and the severe pain associated with tissue toxicity.^[22] In some cases, exposures can lead to hypocalcemia. Thus, hydrofluoric acid exposure is often treated with calcium gluconate, a source of Ca²⁺ that sequesters the fluoride ions. HF chemical burns can be treated with a water wash and 2.5% calcium gluconate gel^[23]^[24]^[25] or special rinsing solutions.^[26]^[27] However, because it is absorbed, medical treatment is necessary;^[21] rinsing off is not enough. Intra-arterial infusions of calcium chloride have also shown great effectiveness in treating burns.^[28]

Hydrogen fluoride is generated upon combustion of many fluorine-containing compounds such as products containing Viton and polytetrafluoroethylene (Teflon) parts.^[29] Hydrofluorocarbons in automatic fire suppression systems can release hydrogen fluoride at high temperatures, and this has led to deaths from acute respiratory failure in military personnel when a rocket-propelled grenade hit the fire suppression system in their vehicle.^[30]

Acidity

Unlike other hydrohalic acids, such as hydrochloric acid, hydrogen fluoride is only a weak acid in dilute aqueous solution.^[31] This is in part a result of the strength of the hydrogen–fluorine bond, but also of other factors such as the tendency of HF, H
₂O, and F⁻
anions to form clusters.^[32] At high concentrations, HF molecules undergo homoassociation to form polyatomic ions (such as bifluoride, HF⁻
₂) and protons, thus greatly increasing the acidity.^[33] This leads to protonation of very strong acids like hydrochloric, sulfuric, or nitric when using concentrated hydrofluoric acid solutions.^[34] Although hydrofluoric acid is regarded as a weak acid, it is very corrosive, even attacking glass when hydrated.^[33]

The acidity of hydrofluoric acid solutions varies with concentration owing to hydrogen-bond interactions of the fluoride ion. Dilute solutions are weakly acidic with an acid ionization constant $K a = 6.6 \times 10 -4$ (or $p K a = 3.18$ ),^[35] in contrast to corresponding solutions of the other hydrogen halides, which are strong acids ( $p K a < 0$ ). Concentrated solutions of hydrogen fluoride are much more strongly acidic than implied by this value, as shown by measurements of the Hammett acidity function H₀^[13](or "effective pH"). The H₀ for 100% HF is estimated to be between −10.2 and −11, comparable to the value −12 for sulfuric acid.^[14]^[15]

In thermodynamic terms, HF solutions are highly non-ideal, with the activity of HF increasing much more rapidly than its concentration. The weak acidity in dilute solution is sometimes attributed to the high H—F bond strength, which combines with the high dissolution enthalpy of HF to outweigh the more negative enthalpy of hydration of the fluoride ion.^[36] Paul Giguère and Sylvia Turrell^[37]^[38] have shown by infrared spectroscopy that the predominant solute species in dilute solution is the hydrogen-bonded ion pair H₃O⁺·F⁻.^[39]

H₂O + HF ⇌ H₃O⁺⋅F⁻

With increasing concentration of HF the concentration of the hydrogen difluoride ion also increases.^[37] The reaction

3 HF

\rightleftharpoons

HF₂⁻ + H₂F⁺

is an example of homoconjugation.

Production

Hydrofluoric acid is produced by treatment of the mineral fluorite (CaF₂) with concentrated sulfuric acid. When combined at 265 °C, these two substances react to produce hydrogen fluoride and calcium sulfate according to the following chemical equation:

CaF₂ + H₂SO₄ → 2 HF + CaSO₄

Although bulk fluorite is a suitable precursor and a major source of world HF production, HF is also produced as a by-product of the production of phosphoric acid, which is derived from the mineral apatite. Apatite sources typically contain a few percent of fluoroapatite, acid digestion of which releases a gaseous stream consisting of sulfur dioxide (from the H₂SO₄), water, and HF, as well as particulates. After separation from the solids, the gases are treated with sulfuric acid and oleum to afford anhydrous HF. Owing to the corrosive nature of HF, its production is accompanied by the dissolution of silicate minerals, and, in this way, significant amounts of fluorosilicic acid are generated.^[5]

Uses

Hydrofluoric acid has a variety of uses in industry and research. It is used as a starting material or intermediate in industrial chemistry, mining, refining, glass finishing, silicon chip manufacturing, and in cleaning.^[6]

Oil refining

In a standard oil refinery process known as alkylation, isobutane is alkylated with low-molecular-weight alkenes (primarily a mixture of propylene and butylene) in the presence of an acid catalyst derived from hydrofluoric acid. The catalyst protonates the alkenes (propylene, butylene) to produce reactive carbocations, which alkylate isobutane. The reaction is carried out at mild temperatures (0 and 30 °C) in a two-phase reaction.

Production of organofluorine compounds

The principal use of hydrofluoric acid is in organofluorine chemistry. Many organofluorine compounds are prepared using HF as the fluorine source, including Teflon, fluoropolymers, fluorocarbons, and refrigerants such as freon.^[5]

Production of fluorides

Most high-volume inorganic fluoride compounds are prepared from hydrofluoric acid. Foremost are Na₃AlF₆, cryolite, and AlF₃, aluminium trifluoride. A molten mixture of these solids serves as a high-temperature solvent for the production of metallic aluminium. Given concerns about fluorides in the environment, alternative technologies are being sought. Other inorganic fluorides prepared from hydrofluoric acid include sodium fluoride and uranium hexafluoride.^[5]

Etchant and cleaning agent

In metalworking, hydrofluoric acid is used as a pickling agent to remove oxides and other impurities from stainless and carbon steels because of its limited ability to dissolve steel.^{[citation needed]} It is used in the semiconductor industry as a major component of Wright Etch and buffered oxide etch, which are used to clean silicon wafers. In a similar manner it is also used to etch glass by reacting with silicon dioxide to form gaseous or water-soluble silicon fluorides. It can also be used to polish and frost glass.^[6]

SiO₂ + 4 HF → SiF₄(g) + 2 H₂O

SiO₂ + 6 HF → H₂SiF₆ + 2 H₂O

A 5% to 9% hydrofluoric acid gel is also commonly used to etch all ceramic dental restorations to improve bonding.^[40] For similar reasons, dilute hydrofluoric acid is a component of household rust stain remover, in car washes in "wheel cleaner" compounds, in ceramic and fabric rust inhibitors, and in water spot removers.^[6]^[41] Because of its ability to dissolve iron oxides as well as silica-based contaminants, hydrofluoric acid is used in pre-commissioning boilers that produce high-pressure steam.

Niche applications

Because of its ability to dissolve (most) oxides and silicates, hydrofluoric acid is useful for dissolving rock samples (usually powdered) prior to analysis. In similar manner, this acid is used in acid macerations to extract organic fossils from silicate rocks. Fossiliferous rock may be immersed directly into the acid, or a cellulose nitrate film may be applied (dissolved in amyl acetate), which adheres to the organic component and allows the rock to be dissolved around it.^[18]

Diluted hydrofluoric acid (1 to 3 %wt.) is used in the petroleum industry in a mixture with other acids (HCl or organic acids) in order to stimulate the production of water, oil, and gas wells specifically where sandstone is involved.^{[citation needed]}

Hydrofluoric acid is also used by some collectors of antique glass bottles to remove so-called 'sickness' from the glass, caused by acids (usually from the soil in which the bottle was buried) attacking the soda content of the glass.^{[citation needed]}

Offset printing companies use hydrofluoric acid to remove unwanted images from printing plates. Felt-tip markers called "deletion pens" are available to make the process safer for the worker.^{[citation needed]}

Health and safety

In addition to being a highly corrosive liquid, hydrofluoric acid is also a powerful contact poison. Because of the ability of hydrofluoric acid to penetrate tissue, poisoning can occur readily through exposure of skin or eyes, or when inhaled or swallowed. Symptoms of exposure to hydrofluoric acid may not be immediately evident, and this can provide false reassurance to victims, causing them to delay medical treatment.^[19] Despite having an irritating odor, HF may reach dangerous levels without an obvious odor.^[6] HF interferes with nerve function, meaning that burns may not initially be painful. Accidental exposures can go unnoticed, delaying treatment and increasing the extent and seriousness of the injury.^[19] Symptoms of HF exposure include irritation of the eyes, skin, nose, and throat, eye and skin burns, rhinitis, bronchitis, pulmonary edema (fluid buildup in the lungs), and bone damage.^[42]

Once absorbed into blood through the skin, it reacts with blood calcium and may cause cardiac arrest. Burns with areas larger than 160 cm² (25 square inches) have the potential to cause serious systemic toxicity from interference with blood and tissue calcium levels.^[21] In the body, hydrofluoric acid reacts with the ubiquitous biologically important ions Ca²⁺ and Mg²⁺. Formation of insoluble calcium fluoride is proposed as the etiology for both precipitous fall in serum calcium and the severe pain associated with tissue toxicity.^[22] In some cases, exposures can lead to hypocalcemia. Thus, hydrofluoric acid exposure is often treated with calcium gluconate, a source of Ca²⁺ that sequesters the fluoride ions. HF chemical burns can be treated with a water wash and 2.5% calcium gluconate gel^[23]^[24]^[43] or special rinsing solutions.^[26]^[44] However, because it is absorbed, medical treatment is necessary;^[21] rinsing off is not enough. Intra-arterial infusions of calcium chloride have also shown great effectiveness in treating burns.^[45]

Hydrogen fluoride is generated upon combustion of many fluorine-containing compounds such as products containing Viton and polytetrafluoroethylene (Teflon) parts.^[46] Hydrofluorocarbons in automatic fire suppression systems can release hydrogen fluoride at high temperatures, and this has led to deaths from acute respiratory failure in military personnel when a rocket-propelled grenade hit the fire suppression system in their vehicle.^[30] Hydrofluoric acid can be released from volcanoes, sea salt aerosol, and from welding or manufacturing processes.^[6]

References

^ Favre, Henri A.; Powell, Warren H., eds. (2014). Nomenclature of Organic Chemistry: IUPAC Recommendations and Preferred Names 2013. Cambridge: The Royal Society of Chemistry. p. 131. ISBN 9781849733069.
^ Harris, Daniel C. (2010). Quantitative Chemical Analysis (8th international ed.). New York: W. H. Freeman. pp. AP14. ISBN 978-1429263092.
^ "Hydrofluoric Acid". PubChem. National Institute of Health. Retrieved October 12, 2017.
^ Greenwood, Norman N.; Earnshaw, Alan (1984). Chemistry of the Elements. Oxford: Pergamon Press. p. 921. ISBN 978-0-08-022057-4.
^ ^a ^b ^c ^d ^e ^f Aigueperse, Jean; Mollard, Paul; Devilliers, Didier; Chemla, Marius; Faron, Robert; Romano, René; Cuer, Jean Pierre (June 15, 2000), Fluorine Compounds, Inorganic, Weinheim, Germany: Wiley-VCH Verlag GmbH & Co. KGaA, doi:10.1002/14356007.a11_307, ISBN 3-527-30673-0
^ ^a ^b ^c ^d ^e ^f ^g ^h "CDC – The Emergency Response Safety and Health Database: Systemic Agent: HYDROGEN FLUORIDE/ HYDROFLUORIC ACID – NIOSH". www.cdc.gov. Retrieved 2015-12-04.
^ Ralph H. Petrucci; William S. Harwood; Jeffry D. Madura (2007). General chemistry: principles and modern applications. Pearson/Prentice Hall. p. 691. ISBN 978-0-13-149330-8. Retrieved 22 August 2011.
^ Giguère, Paul A.; Turrell, Sylvia (1980). "The nature of hydrofluoric acid. A spectroscopic study of the proton-transfer complex H₃O⁺...F⁻". J. Am. Chem. Soc. 102 (17): 5473. doi:10.1021/ja00537a008. {{cite journal}}: templatestyles stripmarker in |title= at position 87 (help)
^ Radu Iftimie; Vibin Thomas; Sylvain Plessis; Patrick Marchand; Patrick Ayotte (2008). "Spectral Signatures and Molecular Origin of Acid Dissociation Intermediates". J. Am. Chem. Soc. 130 (18): 5901–7. doi:10.1021/ja077846o. PMID 18386892.
^ ^a ^b Mootz, D. (1981). "Crystallochemical Correlate to the Anomaly of Hydrofluoric Acid". Angew. Chem. Int. Ed. Engl. 20 (123): 791. doi:10.1002/anie.198107911.
^ Prkić, Ante; Giljanović, Josipa; Bralić, Marija; Boban, Katarina (2012). "Direct Potentiometric Determination of Fluoride Species by Using Ion-Selective Fluoride Electrode" (PDF). Int. J. Electrochem. Sci. 7: 1170–1179.
^ Bunič, Tina; Tramšek, Melita; Goreshnik, Evgeny; Žemva, Boris (2006). "Barium trihydrogen tetrafluoride of the composition Ba(H₃F₄)₂: The first example of homoleptic HF metal environment". Solid State Sciences. 8 (8): 927–931. Bibcode:2006SSSci...8..927B. doi:10.1016/j.solidstatesciences.2006.02.045.
^ ^a ^b Hyman, Herbert H.; Kilpatrick, Martin; Katz, Joseph J. (1957). "The Hammett Acidity Function H₀ for Hydrofluoric Acid Solutions". Journal of the American Chemical Society. 79 (14). American Chemical Society (ACS): 3668–3671. doi:10.1021/ja01571a016. ISSN 0002-7863.
^ ^a ^b Jolly, William L. (1991). Modern Inorganic Chemistry. McGraw-Hill. p. 203. ISBN 0-07-032768-8. OCLC 22861992.
^ ^a ^b Cotton, F. A.; Wilkinson, G. (1988). Advanced Inorganic Chemistry. New York: Wiley. p. 109. ISBN 0-471-84997-9. OCLC 16580057. {{cite book}}: Invalid |ref=harv (help)
^ Craig, Robert (2006). Craig's restorative dental materials. St. Louis, Mo: Mosby Elsevier. ISBN 0-323-03606-6. OCLC 68207297.
^ Strachan, John (January 1999). "A deadly rinse: The dangers of hydrofluoric acid". Professional Carwashing & Detailing. 23 (1). Archived from the original on April 25, 2012.
^ ^a ^b Edwards, D. (1982). "Fragmentary non-vascular plant microfossils from the late Silurian of Wales". Botanical Journal of the Linnean Society. 84 (3): 223–256. doi:10.1111/j.1095-8339.1982.tb00536.x.
^ ^a ^b ^c ^d Yamashita M, Yamashita M, Suzuki M, Hirai H, Kajigaya H (2001). "Ionophoretic delivery of calcium for experimental hydrofluoric acid burns". Crit. Care Med. 29 (8): 1575–8. doi:10.1097/00003246-200108000-00013. PMID 11505130.
^ "CDC – NIOSH Pocket Guide to Chemical Hazards – Hydrogen fluoride". www.cdc.gov. Retrieved 2015-11-28.
^ ^a ^b ^c ^d "Recommended Medical Treatment for Hydrofluoric Acid Exposure" (PDF). Honeywell Specialty Materials. Archived from the original (PDF) on March 25, 2009. Retrieved 2009-05-06.
^ ^a ^b Hoffman, Robert S. et al. (2007) Goldfrank's Manual of Toxicologic Emergencies. New York: McGraw-Hill Professional, p. 1333, ISBN 0071509577.
^ ^a ^b el Saadi MS, Hall AH, Hall PK, Riggs BS, Augenstein WL, Rumack BH (1989). "Hydrofluoric acid dermal exposure". Vet Hum Toxicol. 31 (3): 243–7. PMID 2741315.
^ ^a ^b Roblin I, Urban M, Flicoteau D, Martin C, Pradeau D (2006). "Topical treatment of experimental hydrofluoric acid skin burns by 2.5% calcium gluconate". J Burn Care Res. 27 (6): 889–94. doi:10.1097/01.BCR.0000245767.54278.09. PMID 17091088.
^ "Calcium Gluconate Gel as an Antidote to HF Acid Burns". Northwestern University. Archived from the original on April 8, 2009. Retrieved 2012-10-01.
^ ^a ^b Hultén P, Höjer J, Ludwigs U, Janson A (2004). "Hexafluorine vs. standard decontamination to reduce systemic toxicity after dermal exposure to hydrofluoric acid". J. Toxicol. Clin. Toxicol. 42 (4): 355–61. doi:10.1081/CLT-120039541. PMID 15461243.
^ "News & Views". Chemical Health and Safety. 12 (5): 35–37. September–October 2005. doi:10.1016/j.chs.2005.07.007.
^ Siegel DC, Heard JM (March 1992). "Intra-arterial calcium infusion for hydrofluoric acid burns". Aviat Space Environ Med. 63 (3): 206–11. PMID 1567323.
^ Koch, Ernst-Christian (2002). "Metal-Fluorocarbon-Pyrolants IV: Thermochemical and Combustion Behaviour of Magnesium/Teflon/Viton (MTV)". Propellants, Explosives, Pyrotechnics. 27 (6): 340–351. doi:10.1002/prep.200290004.
^ ^a ^b Chauviere, Matt; Zierold, Dustin (2011-09-17). "Hydrogen Fluoride Inhalation Injury from a Fire Suppression System". NATO. Retrieved 2013-08-22.
^ Wiberg, Egon; Wiberg, Nils; Holleman, Arnold Frederick (2001). Inorganic Chemistry. San Diego: Academic Press. p. 425. ISBN 978-0-12-352651-9.
^ Clark, Jim (2002). "The acidity of the hydrogen halides". Retrieved 4 September 2011.
^ ^a ^b Chambers, C.; Holliday, A. K. (1975). Modern inorganic chemistry (An intermediate text) (PDF). The Butterworth Group. pp. 328–329. Archived from the original (PDF) on 2013-03-23.
^ Hannan, Henry J. (2010). Course in chemistry for IIT-JEE 2011. Tata McGraw Hill Education Private Limited. pp. 15–22. ISBN 9780070703360.
^ Ralph H. Petrucci; William S. Harwood; Jeffry D. Madura (2007). General chemistry: principles and modern applications. Pearson/Prentice Hall. p. 691. ISBN 978-0-13-149330-8. Retrieved 22 August 2011.
^ C. E. Housecroft and A. G. Sharpe "Inorganic Chemistry" (Pearson Prentice Hall, 2nd ed. 2005), p. 170.
^ ^a ^b Giguère, Paul A.; Turrell, Sylvia (1980). "The nature of hydrofluoric acid. A spectroscopic study of the proton-transfer complex H₃O⁺...F⁻". J. Am. Chem. Soc. 102 (17): 5473. doi:10.1021/ja00537a008. {{cite journal}}: templatestyles stripmarker in |title= at position 87 (help)
^ Radu Iftimie; Vibin Thomas; Sylvain Plessis; Patrick Marchand; Patrick Ayotte (2008). "Spectral Signatures and Molecular Origin of Acid Dissociation Intermediates". J. Am. Chem. Soc. 130 (18): 5901–7. doi:10.1021/ja077846o. PMID 18386892.
^ Cotton & Wilkinson (1988), p. 104 harvp error: multiple targets (2×): CITEREFCottonWilkinson1988 (help)
^ Craig, Robert (2006). Craig's restorative dental materials. St. Louis, Mo: Mosby Elsevier. ISBN 0-323-03606-6. OCLC 68207297.
^ Strachan, John (January 1999). "A deadly rinse: The dangers of hydrofluoric acid". Professional Carwashing & Detailing. 23 (1). Archived from the original on April 25, 2012.
^ "CDC – NIOSH Pocket Guide to Chemical Hazards – Hydrogen fluoride". www.cdc.gov. Retrieved 2015-11-28.
^ "Calcium Gluconate Gel as an Antidote to HF Acid Burns". Northwestern University. Archived from the original on April 8, 2009. Retrieved 2012-10-01.
^ "News & Views". Chemical Health and Safety. 12 (5): 35–37. September–October 2005. doi:10.1016/j.chs.2005.07.007.
^ Siegel DC, Heard JM (March 1992). "Intra-arterial calcium infusion for hydrofluoric acid burns". Aviat Space Environ Med. 63 (3): 206–11. PMID 1567323.
^ Koch, Ernst-Christian (2002). "Metal-Fluorocarbon-Pyrolants IV: Thermochemical and Combustion Behaviour of Magnesium/Teflon/Viton (MTV)". Propellants, Explosives, Pyrotechnics. 27 (6): 340–351. doi:10.1002/prep.200290004.

External links

International Chemical Safety Card 0283
NIOSH Pocket Guide to Chemical Hazards
CID 14917 from PubChem (HF)
CID 144681 from PubChem (5HF)
CID 141165 from PubChem (6HF)
CID 144682 from PubChem (7HF)
"Hydrofluoric Acid Burn", The New England Journal of Medicine—Acid burn case study

[1] Favre, Henri A.; Powell, Warren H., eds. (2014). Nomenclature of Organic Chemistry: IUPAC Recommendations and Preferred Names 2013. Cambridge: The Royal Society of Chemistry. p. 131. ISBN 9781849733069.

[2] Harris, Daniel C. (2010). Quantitative Chemical Analysis (8th international ed.). New York: W. H. Freeman. pp. AP14. ISBN 978-1429263092.

[3] "Hydrofluoric Acid". PubChem. National Institute of Health. Retrieved October 12, 2017.

[4] Greenwood, Norman N.; Earnshaw, Alan (1984). Chemistry of the Elements. Oxford: Pergamon Press. p. 921. ISBN 978-0-08-022057-4.

[Ullmann-5] ^ ^a ^b ^c ^d ^e ^f Aigueperse, Jean; Mollard, Paul; Devilliers, Didier; Chemla, Marius; Faron, Robert; Romano, René; Cuer, Jean Pierre (June 15, 2000), Fluorine Compounds, Inorganic, Weinheim, Germany: Wiley-VCH Verlag GmbH & Co. KGaA, doi:10.1002/14356007.a11_307, ISBN 3-527-30673-0

[:0-6] ^ ^a ^b ^c ^d ^e ^f ^g ^h "CDC – The Emergency Response Safety and Health Database: Systemic Agent: HYDROGEN FLUORIDE/ HYDROFLUORIC ACID – NIOSH". www.cdc.gov. Retrieved 2015-12-04.

[7] Ralph H. Petrucci; William S. Harwood; Jeffry D. Madura (2007). General chemistry: principles and modern applications. Pearson/Prentice Hall. p. 691. ISBN 978-0-13-149330-8. Retrieved 22 August 2011.

[8] Giguère, Paul A.; Turrell, Sylvia (1980). "The nature of hydrofluoric acid. A spectroscopic study of the proton-transfer complex H₃O⁺...F⁻". J. Am. Chem. Soc. 102 (17): 5473. doi:10.1021/ja00537a008. {{cite journal}}: templatestyles stripmarker in |title= at position 87 (help)

[9] Radu Iftimie; Vibin Thomas; Sylvain Plessis; Patrick Marchand; Patrick Ayotte (2008). "Spectral Signatures and Molecular Origin of Acid Dissociation Intermediates". J. Am. Chem. Soc. 130 (18): 5901–7. doi:10.1021/ja077846o. PMID 18386892.

[mootz-10] Mootz, D. (1981). "Crystallochemical Correlate to the Anomaly of Hydrofluoric Acid". Angew. Chem. Int. Ed. Engl. 20 (123): 791. doi:10.1002/anie.198107911.

[11] Prkić, Ante; Giljanović, Josipa; Bralić, Marija; Boban, Katarina (2012). "Direct Potentiometric Determination of Fluoride Species by Using Ion-Selective Fluoride Electrode" (PDF). Int. J. Electrochem. Sci. 7: 1170–1179.

[12] Bunič, Tina; Tramšek, Melita; Goreshnik, Evgeny; Žemva, Boris (2006). "Barium trihydrogen tetrafluoride of the composition Ba(H₃F₄)₂: The first example of homoleptic HF metal environment". Solid State Sciences. 8 (8): 927–931. Bibcode:2006SSSci...8..927B. doi:10.1016/j.solidstatesciences.2006.02.045.

[HymanKilpatrick1957-13] Hyman, Herbert H.; Kilpatrick, Martin; Katz, Joseph J. (1957). "The Hammett Acidity Function H₀ for Hydrofluoric Acid Solutions". Journal of the American Chemical Society. 79 (14). American Chemical Society (ACS): 3668–3671. doi:10.1021/ja01571a016. ISSN 0002-7863.

[Jolly-14] Jolly, William L. (1991). Modern Inorganic Chemistry. McGraw-Hill. p. 203. ISBN 0-07-032768-8. OCLC 22861992.

[Cotton_109-15] Cotton, F. A.; Wilkinson, G. (1988). Advanced Inorganic Chemistry. New York: Wiley. p. 109. ISBN 0-471-84997-9. OCLC 16580057. {{cite book}}: Invalid |ref=harv (help)

[16] Craig, Robert (2006). Craig's restorative dental materials. St. Louis, Mo: Mosby Elsevier. ISBN 0-323-03606-6. OCLC 68207297.

[17] Strachan, John (January 1999). "A deadly rinse: The dangers of hydrofluoric acid". Professional Carwashing & Detailing. 23 (1). Archived from the original on April 25, 2012.

[Edwards1982-18] Edwards, D. (1982). "Fragmentary non-vascular plant microfossils from the late Silurian of Wales". Botanical Journal of the Linnean Society. 84 (3): 223–256. doi:10.1111/j.1095-8339.1982.tb00536.x.

[pmid11505130-19] Yamashita M, Yamashita M, Suzuki M, Hirai H, Kajigaya H (2001). "Ionophoretic delivery of calcium for experimental hydrofluoric acid burns". Crit. Care Med. 29 (8): 1575–8. doi:10.1097/00003246-200108000-00013. PMID 11505130.

[20] "CDC – NIOSH Pocket Guide to Chemical Hazards – Hydrogen fluoride". www.cdc.gov. Retrieved 2015-11-28.

[RMTHFE-21] "Recommended Medical Treatment for Hydrofluoric Acid Exposure" (PDF). Honeywell Specialty Materials. Archived from the original (PDF) on March 25, 2009. Retrieved 2009-05-06.

[Goldfrank-22] Hoffman, Robert S. et al. (2007) Goldfrank's Manual of Toxicologic Emergencies. New York: McGraw-Hill Professional, p. 1333, ISBN 0071509577.

[pmid2741315-23] Saadi MS, Hall AH, Hall PK, Riggs BS, Augenstein WL, Rumack BH (1989). "Hydrofluoric acid dermal exposure". Vet Hum Toxicol. 31 (3): 243–7. PMID 2741315.

[pmid17091088-24] Roblin I, Urban M, Flicoteau D, Martin C, Pradeau D (2006). "Topical treatment of experimental hydrofluoric acid skin burns by 2.5% calcium gluconate". J Burn Care Res. 27 (6): 889–94. doi:10.1097/01.BCR.0000245767.54278.09. PMID 17091088.

[25] "Calcium Gluconate Gel as an Antidote to HF Acid Burns". Northwestern University. Archived from the original on April 8, 2009. Retrieved 2012-10-01.

[pmid15461243-26] Hultén P, Höjer J, Ludwigs U, Janson A (2004). "Hexafluorine vs. standard decontamination to reduce systemic toxicity after dermal exposure to hydrofluoric acid". J. Toxicol. Clin. Toxicol. 42 (4): 355–61. doi:10.1081/CLT-120039541. PMID 15461243.

[27] "News & Views". Chemical Health and Safety. 12 (5): 35–37. September–October 2005. doi:10.1016/j.chs.2005.07.007.

[28] Siegel DC, Heard JM (March 1992). "Intra-arterial calcium infusion for hydrofluoric acid burns". Aviat Space Environ Med. 63 (3): 206–11. PMID 1567323.

[29] Koch, Ernst-Christian (2002). "Metal-Fluorocarbon-Pyrolants IV: Thermochemical and Combustion Behaviour of Magnesium/Teflon/Viton (MTV)". Propellants, Explosives, Pyrotechnics. 27 (6): 340–351. doi:10.1002/prep.200290004.

[HFC-30] Chauviere, Matt; Zierold, Dustin (2011-09-17). "Hydrogen Fluoride Inhalation Injury from a Fire Suppression System". NATO. Retrieved 2013-08-22.

[31] Wiberg, Egon; Wiberg, Nils; Holleman, Arnold Frederick (2001). Inorganic Chemistry. San Diego: Academic Press. p. 425. ISBN 978-0-12-352651-9.

[32] Clark, Jim (2002). "The acidity of the hydrogen halides". Retrieved 4 September 2011.

[H+-33] Chambers, C.; Holliday, A. K. (1975). Modern inorganic chemistry (An intermediate text) (PDF). The Butterworth Group. pp. 328–329. Archived from the original (PDF) on 2013-03-23.

[34] Hannan, Henry J. (2010). Course in chemistry for IIT-JEE 2011. Tata McGraw Hill Education Private Limited. pp. 15–22. ISBN 9780070703360.

[35] Ralph H. Petrucci; William S. Harwood; Jeffry D. Madura (2007). General chemistry: principles and modern applications. Pearson/Prentice Hall. p. 691. ISBN 978-0-13-149330-8. Retrieved 22 August 2011.

[36] C. E. Housecroft and A. G. Sharpe "Inorganic Chemistry" (Pearson Prentice Hall, 2nd ed. 2005), p. 170.

[Giguère-37] Giguère, Paul A.; Turrell, Sylvia (1980). "The nature of hydrofluoric acid. A spectroscopic study of the proton-transfer complex H₃O⁺...F⁻". J. Am. Chem. Soc. 102 (17): 5473. doi:10.1021/ja00537a008. {{cite journal}}: templatestyles stripmarker in |title= at position 87 (help)

[38] Radu Iftimie; Vibin Thomas; Sylvain Plessis; Patrick Marchand; Patrick Ayotte (2008). "Spectral Signatures and Molecular Origin of Acid Dissociation Intermediates". J. Am. Chem. Soc. 130 (18): 5901–7. doi:10.1021/ja077846o. PMID 18386892.

[Cotton_104-39] Cotton & Wilkinson (1988), p. 104 harvp error: multiple targets (2×): CITEREFCottonWilkinson1988 (help)

[40] Craig, Robert (2006). Craig's restorative dental materials. St. Louis, Mo: Mosby Elsevier. ISBN 0-323-03606-6. OCLC 68207297.

[41] Strachan, John (January 1999). "A deadly rinse: The dangers of hydrofluoric acid". Professional Carwashing & Detailing. 23 (1). Archived from the original on April 25, 2012.

[42] "CDC – NIOSH Pocket Guide to Chemical Hazards – Hydrogen fluoride". www.cdc.gov. Retrieved 2015-11-28.

[43] "Calcium Gluconate Gel as an Antidote to HF Acid Burns". Northwestern University. Archived from the original on April 8, 2009. Retrieved 2012-10-01.

[44] "News & Views". Chemical Health and Safety. 12 (5): 35–37. September–October 2005. doi:10.1016/j.chs.2005.07.007.

[45] Siegel DC, Heard JM (March 1992). "Intra-arterial calcium infusion for hydrofluoric acid burns". Aviat Space Environ Med. 63 (3): 206–11. PMID 1567323.

[46] Koch, Ernst-Christian (2002). "Metal-Fluorocarbon-Pyrolants IV: Thermochemical and Combustion Behaviour of Magnesium/Teflon/Viton (MTV)". Propellants, Explosives, Pyrotechnics. 27 (6): 340–351. doi:10.1002/prep.200290004.

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@@ Line 30: / Line 30: @@
 ==Production==
-Hydrofluoric acid was first prepared in 1771, by [[Carl Wilhelm Scheele]] .<ref>{{Greenwood&Earnshaw1st|page=921}}</ref> It is now mainly produced by treatment of the mineral [[fluorite]] CaF<sub>2</sub> with concentrated [[sulfuric acid]] at ca. 265&nbsp;°C. This produces hydrogen fluoride and [[calcium sulfate]] according to the following [[chemical equation]]:
+Hydrofluoric acid was first prepared in 1771, by [[Carl Wilhelm Scheele]] .<ref>{{Greenwood&Earnshaw1st|page=921}}</ref> It is now mainly produced by treatment of the mineral [[fluorite]], CaF<sub>2</sub>, with concentrated [[sulfuric acid]] at ca. 265&nbsp;°C.
 :CaF<sub>2</sub>  +  H<sub>2</sub>SO<sub>4</sub>  →  2 HF  +  CaSO<sub>4</sub>
-The acid is also produced as a by-product of the production of [[phosphoric acid]] from [[apatite]]. Apatite sources typically contain a few percent of [[fluoroapatite]], acid digestion of which releases a gaseous stream consisting of [[sulfur dioxide]] (from the H<sub>2</sub>SO<sub>4</sub>), water, and HF, as well as particulates.  After separation from the solids, the gases are treated with sulfuric acid and [[oleum]] to afford [[anhydrous]] HF. Owing to the corrosive nature of HF, its production is accompanied by the dissolution of silicate minerals, and, in this way, significant amounts of [[fluorosilicic acid]] are generated.<ref name="Ullmann"> {{citation|last=Aigueperse|first=Jean|title=Fluorine Compounds, Inorganic|date=June 15, 2000|location=Weinheim, Germany|publisher=Wiley-VCH Verlag GmbH & Co. KGaA|doi=10.1002/14356007.a11_307|isbn=3-527-30673-0|last2=Mollard|first2=Paul|last3=Devilliers|first3=Didier|last4=Chemla|first4=Marius|last5=Faron|first5=Robert|last6=Romano|first6=René|last7=Cuer|first7=Jean Pierre}}</ref>
+The acid is also a by-product of the production of [[phosphoric acid]] from [[apatite]]/[[fluoroapatite]]. Digestion of the mineral with sulfuric acid at elevated temperatures releases a mixture of gases, including hydrogen fluoride, which may be recovered. <ref name=Ullmann> {{citation | last=Aigueperse | first=Jean | last2=Mollard | first2=Paul | last3=Devilliers | first3=Didier | last4=Chemla | first4=Marius | last5=Faron | first5=Robert | last6=Romano | first6=René | last7=Cuer | first7=Jean Pierre | title=Fluorine Compounds, Inorganic | publisher=Wiley-VCH Verlag GmbH & Co. KGaA | location=Weinheim, Germany | date=June 15, 2000 | isbn=3-527-30673-0 | doi=10.1002/14356007.a11_307}}</ref>
 Because of its high reactivity toward glass, hydrofluoric acid is stored in [[plastic]] containers.<ref name=Ullmann/><ref name=":0">{{Cite web|title = CDC – The Emergency Response Safety and Health Database: Systemic Agent: HYDROGEN FLUORIDE/ HYDROFLUORIC ACID – NIOSH|url = https://www.cdc.gov/niosh/ershdb/EmergencyResponseCard_29750030.html|website = www.cdc.gov|accessdate = 2015-12-04}}</ref>
@@ Line 61: / Line 61: @@
 Solutions of hydrofluoric acid attack glass, so they are stored and used in vessels made of [[teflon]]. They attack [[human skin]], so must be handled with great care: see [[#Health and Safety]], below.
+==Uses==
+Hydrofluoric acid has a variety of uses in industry and research. The principal use is in [[organofluorine chemistry]] for the production of [[Polytetrafluoroethylene|Teflon]], [[fluoropolymer]]s, [[fluorocarbon]]s, and [[refrigeration|refrigerants]] such as [[freon]].<ref name=Ullmann/> Most high-volume inorganic fluoride compounds are prepared from hydrofluoric acid.  Foremost are Na<sub>3</sub>AlF<sub>6</sub>, [[cryolite]], and AlF<sub>3</sub>, [[aluminium trifluoride]]. Metallic [[aluminium]] is produced by electrolysis of a molten mixture of these compounds. The acid is used in the production of [[uranium hexafluoride]].
+[[File:Wet etching tanks at LAAS (6 inches) 0468.jpg|thumbnail|right|Wet etching tanks]]It is used as an etchant and cleaning agent. In metalworking, hydrofluoric acid is used as a [[Pickling (metal)|pickling agent]] to remove oxides and other impurities from [[stainless steel|stainless]] and [[carbon steel]]s because of its limited ability to dissolve steel.{{citation needed|date=March 2014}} It is used in the [[semiconductor]] industry as a major component of [[Wright Etch]] and [[buffered oxide etch]], which are used to clean [[silicon wafer]]s.
+A 5% to 9% hydrofluoric acid gel is also commonly used to etch all ceramic dental restorations to improve bonding.<ref>{{cite book | last=Craig | first=Robert | title=Craig's restorative dental materials | publisher=Mosby Elsevier | location=St. Louis, Mo | year=2006 | isbn=0-323-03606-6 | oclc=68207297}}<!-- Powers, John M. and Sakaguchi, Ronald L. (2006) ''Craig's Restorative Dental Materials'', 12th ed., Mosby, {{ISBN|0323036066}} p. 10.5.3--></ref> For similar reasons, dilute hydrofluoric acid is a component of household rust stain remover, in [[car wash]]es in "wheel cleaner" compounds, in ceramic and fabric rust inhibitors, and in water spot removers.<ref name=":0" /><ref>{{cite journal|last=Strachan |first=John |title=A deadly rinse: The dangers of hydrofluoric acid |journal=Professional Carwashing & Detailing |date=January 1999 |url=http://secure.gvmg.com/carwash/articleprint.asp?print=1&IndexID=4230101 |volume=23 |issue=1 |url-status=dead |archiveurl=https://web.archive.org/web/20120425234944/http://secure.gvmg.com/carwash/articleprint.asp?print=1&IndexID=4230101 |archivedate=April 25, 2012 }}</ref> Because of its ability to dissolve iron oxides as well as silica-based contaminants, hydrofluoric acid is used in pre-commissioning boilers that produce high-pressure steam.
+Because of its ability to dissolve (most) oxides and silicates, hydrofluoric acid is useful for dissolving rock samples (usually powdered) prior to analysis. In similar manner, this acid is used in [[acid maceration]]s to extract organic fossils from silicate rocks.  Fossiliferous rock may be immersed directly into the acid, or a [[cellulose nitrate]] film may be applied (dissolved in [[amyl acetate]]), which adheres to the organic component and allows the rock to be dissolved around it.<ref name="Edwards1982" />
+Diluted hydrofluoric acid (1 to 3 %wt.) is used in the [[petroleum industry]] in a mixture with other acids (HCl or organic acids) in order to stimulate the production of water, oil, and gas wells specifically where sandstone is involved.{{Citation needed|date=October 2009}}
+Hydrofluoric acid is also used by some collectors of antique glass bottles to remove so-called 'sickness' from the glass, caused by acids (usually from the soil in which the bottle was buried) attacking the soda content of the glass.{{Citation needed|date= February 2011}}
+Offset printing companies use hydrofluoric acid to remove unwanted images from printing plates. Felt-tip markers called "deletion pens" are available to make the process safer for the worker.{{Citation needed|date=July 2015}}
+==Health and safety==
+[[File:HF burned hands.jpg|thumb|alt=left and right hands, two views, burned fingers|HF burns, one day after exposure]]
+In addition to being a highly [[corrosive]] liquid, hydrofluoric acid is also a powerful contact [[poison]].  Because of the ability of hydrofluoric acid to penetrate tissue, poisoning can occur readily through exposure of skin or eyes, or when inhaled or swallowed. Symptoms of exposure to hydrofluoric acid may not be immediately evident, and this can provide false reassurance to victims, causing them to delay medical treatment.<ref name="pmid11505130" /> Despite having an irritating odor, HF may reach dangerous levels without an obvious odor.<ref name=":0" /> HF interferes with nerve function, meaning that burns may not initially be painful. Accidental exposures can go unnoticed, delaying treatment and increasing the extent and seriousness of the injury.<ref name="pmid11505130"/> Symptoms of HF exposure include irritation of the eyes, skin, nose, and throat, eye and skin burns, [[rhinitis]], [[bronchitis]], [[pulmonary edema]] (fluid buildup in the lungs), and bone damage.<ref>{{Cite web|title = CDC – NIOSH Pocket Guide to Chemical Hazards – Hydrogen fluoride|url = https://www.cdc.gov/niosh/npg/npgd0334.html|website = www.cdc.gov|accessdate = 2015-11-28}}</ref>
+Once absorbed into blood through the skin, it reacts with blood calcium and may cause cardiac arrest. Burns with areas larger than 160&nbsp;cm<sup>2</sup> (25 square inches) have the potential to cause serious systemic toxicity from interference with blood and tissue calcium levels.<ref name="RMTHFE"/>  In the body, hydrofluoric acid reacts with the ubiquitous biologically important [[ion]]s [[calcium|Ca<sup>2+</sup>]] and [[magnesium|Mg<sup>2+</sup>]]. Formation of insoluble [[calcium fluoride]] is proposed as the etiology for both precipitous fall in serum calcium and the severe pain associated with tissue toxicity.<ref name="Goldfrank" /> In some cases, exposures can lead to [[hypocalcemia]]. Thus, hydrofluoric acid exposure is often treated with [[calcium gluconate]], a source of Ca<sup>2+</sup> that sequesters the fluoride ions. HF [[chemical burn]]s can be treated with a water wash and 2.5% calcium gluconate gel<ref name="pmid2741315" /><ref name="pmid17091088">{{cite journal |vauthors=Roblin I, Urban M, Flicoteau D, Martin C, Pradeau D|title=Topical treatment of experimental hydrofluoric acid skin burns by 2.5% calcium gluconate |journal=J Burn Care Res |volume=27 |issue=6 |pages=889–94 |year=2006 |pmid=17091088 |doi=10.1097/01.BCR.0000245767.54278.09}}</ref><ref>{{cite web|url=http://www.research.northwestern.edu/ors/emerg/firstaid/calglugel.htm |title=Calcium Gluconate Gel as an Antidote to HF Acid Burns |accessdate=2012-10-01 |publisher=Northwestern University |url-status=dead |archiveurl=https://web.archive.org/web/20090408083821/http://www.research.northwestern.edu/ors/emerg/firstaid/calglugel.htm |archivedate=April 8, 2009 }}</ref> or special rinsing solutions.<ref name="pmid15461243" /><ref>{{cite journal|title=News & Views|journal=Chemical Health and Safety |date=September–October 2005|volume= 12|issue=5|pages=35–37| doi = 10.1016/j.chs.2005.07.007 }}</ref> However, because it is absorbed, medical treatment is necessary;<ref name="RMTHFE" /> rinsing off is not enough. Intra-arterial infusions of calcium chloride have also shown great effectiveness in treating burns.<ref>{{Cite journal|pmid=1567323 |title=Intra-arterial calcium infusion for hydrofluoric acid burns | volume=63|issue=3|date=March 1992|vauthors=Siegel DC, Heard JM|journal=Aviat Space Environ Med|pages=206–11}}</ref>
+Hydrogen fluoride is generated upon combustion of many fluorine-containing compounds such as products containing [[Viton]] and [[Polytetrafluoroethylene| polytetrafluoroethylene (Teflon)]] parts.<ref>{{cite journal|last=Koch|first=Ernst-Christian|title=Metal-Fluorocarbon-Pyrolants IV: Thermochemical and Combustion Behaviour of Magnesium/Teflon/Viton (MTV)| doi = 10.1002/prep.200290004 | journal = [[Propellants, Explosives, Pyrotechnics]] | volume = 27 | year = 2002 | pages = 340–351|issue=6}}</ref> [[Hydrofluorocarbon]]s in [[automatic fire suppression]] systems can release hydrogen fluoride at high temperatures, and this has led to deaths from acute [[respiratory failure]] in military personnel when a [[rocket-propelled grenade]] hit the fire suppression system in their vehicle.<ref name="HFC">{{cite web|url=https://www.sto.nato.int/publications/_layouts/WordViewer.aspx?id=/publications/STO%20Meeting%20Proceedings/RTO-MP-HFM-207/MP-HFM-207-03.doc&Source=https%3A%2F%2Fwww%2Esto%2Enato%2Eint%2Fpublications%2FSTO%2520Meeting%2520Proceedings%2FForms%2FAll%2520MPs%2Easpx%3FRootFolder%3D%252Fpublications%252FSTO%2520Meeting%2520Proceedings%252FRTO%252DMP%252DHFM%252D207%26FolderCTID%3D0x0120D5200078F9E87043356C409A0D30823AFA16F602008CF184CAB7588E468F5E9FA364E05BA5%26View%3D%257B72ED425F%2DC31F%2D451C%2DA545%2D41122BBA61A7%257D&DefaultItemOpen=1&DefaultItemOpen=1|title=Hydrogen Fluoride Inhalation Injury from a Fire Suppression System|author1=Chauviere, Matt  |author2=Zierold, Dustin |date=2011-09-17|publisher=NATO|accessdate=2013-08-22}}</ref>
 ==Acidity==
 Unlike other hydrohalic acids, such as [[hydrochloric acid]], hydrogen fluoride is only a [[weak acid]] in dilute aqueous solution.<ref>{{cite book |last1=Wiberg |first1=Egon |last2=Wiberg |first2=Nils |last3=Holleman |first3=Arnold Frederick |title=Inorganic Chemistry |date=2001 |publisher=Academic Press |isbn=978-0-12-352651-9 |location=San Diego |page=425}}</ref> This is in part a result of the strength of the hydrogen–fluorine bond, but also of other factors such as the tendency of HF, {{chem|H|2|O}}, and {{chem|F|-}} anions to form clusters.<ref>{{cite web |last=Clark |first=Jim |title=The acidity of the hydrogen halides |url=http://www.chemguide.co.uk/inorganic/group7/acidityhx.html |accessdate=4 September 2011 |year=2002}}</ref> At high concentrations, HF molecules undergo [[homoassociation]] to form polyatomic ions (such as [[bifluoride]], {{chem|HF|2|-}}) and [[proton]]s, thus greatly increasing the acidity.<ref name="H+">{{cite book |author1=Chambers, C. |author2=Holliday, A. K. |title=Modern inorganic chemistry (An intermediate text) |year=1975 |publisher=The Butterworth Group |pages=328–329 |url=http://files.rushim.ru/books/neorganika/Chambers.pdf |url-status=dead |archiveurl=https://web.archive.org/web/20130323002902/http://files.rushim.ru/books/neorganika/Chambers.pdf |archivedate=2013-03-23 }}</ref> This leads to [[protonation]] of very strong acids like hydrochloric, sulfuric, or nitric when using concentrated hydrofluoric acid solutions.<ref>{{cite book |author=Hannan, Henry J. |title=Course in chemistry for IIT-JEE 2011 |year=2010 |publisher=Tata McGraw Hill Education Private Limited |isbn=9780070703360 |pages=15–22 |url=https://books.google.com/books?id=wNYMUeCcaSEC&pg=SA15-PA22}}</ref> Although hydrofluoric acid is regarded as a weak acid, it is very corrosive, even attacking glass when hydrated.<ref name="H+"/>
@@ Line 83: / Line 108: @@
 :3 HF <math>\rightleftharpoons</math> HF<sub>2</sub><sup>−</sup> + H<sub>2</sub>F<sup>+</sup>
 is an example of  [[homoassociation|homoconjugation]].
+==Production==
+Hydrofluoric acid is produced by treatment of the mineral [[fluorite]] (CaF<sub>2</sub>) with concentrated [[sulfuric acid]]. When combined at 265&nbsp;°C, these two substances react to produce hydrogen fluoride and [[calcium sulfate]] according to the following [[chemical equation]]:
+:CaF<sub>2</sub>  +  H<sub>2</sub>SO<sub>4</sub>  →  2 HF  +  CaSO<sub>4</sub>
+Although bulk fluorite is a suitable precursor and a major source of world HF production, HF is also produced as a by-product of the production of [[phosphoric acid]], which is derived from the mineral [[apatite]]. Apatite sources typically contain a few percent of [[fluoroapatite]], acid digestion of which releases a gaseous stream consisting of [[sulfur dioxide]] (from the H<sub>2</sub>SO<sub>4</sub>), water, and HF, as well as particulates.  After separation from the solids, the gases are treated with sulfuric acid and [[oleum]] to afford [[Anhydrous|anhydrous]] HF.  Owing to the corrosive nature of HF, its production is accompanied by the dissolution of silicate minerals, and, in this way, significant amounts of [[fluorosilicic acid]] are generated.<ref name="Ullmann" />
 ==Uses==
@@ Line 129: / Line 161: @@
 In addition to being a highly [[corrosive]] liquid, hydrofluoric acid is also a powerful contact [[poison]].  Because of the ability of hydrofluoric acid to penetrate tissue, poisoning can occur readily through exposure of skin or eyes, or when inhaled or swallowed. Symptoms of exposure to hydrofluoric acid may not be immediately evident, and this can provide false reassurance to victims, causing them to delay medical treatment.<ref name="pmid11505130">{{cite journal |vauthors=Yamashita M, Yamashita M, Suzuki M, Hirai H, Kajigaya H|title=Ionophoretic delivery of calcium for experimental hydrofluoric acid burns |journal=Crit. Care Med. |volume=29 |issue=8 |pages=1575–8 |year=2001 |pmid=11505130|doi=10.1097/00003246-200108000-00013}}</ref> Despite having an irritating odor, HF may reach dangerous levels without an obvious odor.<ref name=":0" /> HF interferes with nerve function, meaning that burns may not initially be painful. Accidental exposures can go unnoticed, delaying treatment and increasing the extent and seriousness of the injury.<ref name="pmid11505130"/> Symptoms of HF exposure include irritation of the eyes, skin, nose, and throat, eye and skin burns, [[rhinitis]], [[bronchitis]], [[pulmonary edema]] (fluid buildup in the lungs), and bone damage.<ref>{{Cite web|title = CDC – NIOSH Pocket Guide to Chemical Hazards – Hydrogen fluoride|url = https://www.cdc.gov/niosh/npg/npgd0334.html|website = www.cdc.gov|accessdate = 2015-11-28}}</ref>
-Once absorbed into blood through the skin, it reacts with blood calcium and may cause cardiac arrest. Burns with areas larger than 160&nbsp;cm<sup>2</sup> (25 square inches) have the potential to cause serious systemic toxicity from interference with blood and tissue calcium levels.<ref name="RMTHFE"/>  In the body, hydrofluoric acid reacts with the ubiquitous biologically important [[ion]]s [[calcium|Ca<sup>2+</sup>]] and [[magnesium|Mg<sup>2+</sup>]]. Formation of insoluble [[calcium fluoride]] is proposed as the etiology for both precipitous fall in serum calcium and the severe pain associated with tissue toxicity.<ref name=Goldfrank>Hoffman, Robert S. ''et al.'' (2007) ''Goldfrank's Manual of Toxicologic Emergencies''. New York: McGraw-Hill Professional, p. 1333, {{ISBN|0071509577}}.</ref> In some cases, exposures can lead to [[hypocalcemia]]. Thus, hydrofluoric acid exposure is often treated with [[calcium gluconate]], a source of Ca<sup>2+</sup> that sequesters the fluoride ions. HF [[chemical burn]]s can be treated with a water wash and 2.5% calcium gluconate gel<ref name="pmid2741315">{{cite journal |vauthors=el Saadi MS, Hall AH, Hall PK, Riggs BS, Augenstein WL, Rumack BH|title=Hydrofluoric acid dermal exposure |journal=Vet Hum Toxicol |volume=31 |issue=3 |pages=243–7 |year=1989 |pmid=2741315 |doi=}}</ref><ref name="pmid17091088">{{cite journal|vauthors=Roblin I, Urban M, Flicoteau D, Martin C, Pradeau D|year=2006|title=Topical treatment of experimental hydrofluoric acid skin burns by 2.5% calcium gluconate|journal=J Burn Care Res|volume=27|issue=6|pages=889–94|doi=10.1097/01.BCR.0000245767.54278.09|pmid=17091088}}</ref><ref>{{cite web|url=http://www.research.northwestern.edu/ors/emerg/firstaid/calglugel.htm |title=Calcium Gluconate Gel as an Antidote to HF Acid Burns |accessdate=2012-10-01 |publisher=Northwestern University |url-status=dead |archiveurl=https://web.archive.org/web/20090408083821/http://www.research.northwestern.edu/ors/emerg/firstaid/calglugel.htm |archivedate=April 8, 2009 }}</ref> or special rinsing solutions.<ref name="pmid15461243">{{cite journal |vauthors=Hultén P, Höjer J, Ludwigs U, Janson A|title=Hexafluorine vs. standard decontamination to reduce systemic toxicity after dermal exposure to hydrofluoric acid |journal=J. Toxicol. Clin. Toxicol. |volume=42 |issue=4 |pages=355–61 |year=2004 |pmid=15461243 |doi=10.1081/CLT-120039541}}</ref><ref>{{cite journal|title=News & Views|journal=Chemical Health and Safety |date=September–October 2005|volume= 12|issue=5|pages=35–37| doi = 10.1016/j.chs.2005.07.007 }}</ref> However, because it is absorbed, medical treatment is necessary;<ref name="RMTHFE">{{cite web|url=http://www51.honeywell.com/sm/hfacid/common/documents/HF_medical_book.pdf |title=Recommended Medical Treatment for Hydrofluoric Acid Exposure |accessdate=2009-05-06 |publisher=Honeywell Specialty Materials |url-status=dead |archiveurl=https://web.archive.org/web/20090325112238/http://www51.honeywell.com/sm/hfacid/common/documents/HF_medical_book.pdf |archivedate=March 25, 2009 }}</ref> rinsing off is not enough. Intra-arterial infusions of calcium chloride have also shown great effectiveness in treating burns.<ref>{{Cite journal|pmid=1567323 |title=Intra-arterial calcium infusion for hydrofluoric acid burns | volume=63|issue=3|date=March 1992|vauthors=Siegel DC, Heard JM|journal=Aviat Space Environ Med|pages=206–11}}</ref>
+Once absorbed into blood through the skin, it reacts with blood calcium and may cause cardiac arrest. Burns with areas larger than 160&nbsp;cm<sup>2</sup> (25 square inches) have the potential to cause serious systemic toxicity from interference with blood and tissue calcium levels.<ref name="RMTHFE"/>  In the body, hydrofluoric acid reacts with the ubiquitous biologically important [[ion]]s [[calcium|Ca<sup>2+</sup>]] and [[magnesium|Mg<sup>2+</sup>]]. Formation of insoluble [[calcium fluoride]] is proposed as the etiology for both precipitous fall in serum calcium and the severe pain associated with tissue toxicity.<ref name=Goldfrank>Hoffman, Robert S. ''et al.'' (2007) ''Goldfrank's Manual of Toxicologic Emergencies''. New York: McGraw-Hill Professional, p. 1333, {{ISBN|0071509577}}.</ref> In some cases, exposures can lead to [[hypocalcemia]]. Thus, hydrofluoric acid exposure is often treated with [[calcium gluconate]], a source of Ca<sup>2+</sup> that sequesters the fluoride ions. HF [[chemical burn]]s can be treated with a water wash and 2.5% calcium gluconate gel<ref name="pmid2741315">{{cite journal |vauthors=el Saadi MS, Hall AH, Hall PK, Riggs BS, Augenstein WL, Rumack BH|title=Hydrofluoric acid dermal exposure |journal=Vet Hum Toxicol |volume=31 |issue=3 |pages=243–7 |year=1989 |pmid=2741315 |doi=}}</ref><ref name="pmid17091088" /><ref>{{cite web|url=http://www.research.northwestern.edu/ors/emerg/firstaid/calglugel.htm |title=Calcium Gluconate Gel as an Antidote to HF Acid Burns |accessdate=2012-10-01 |publisher=Northwestern University |url-status=dead |archiveurl=https://web.archive.org/web/20090408083821/http://www.research.northwestern.edu/ors/emerg/firstaid/calglugel.htm |archivedate=April 8, 2009 }}</ref> or special rinsing solutions.<ref name="pmid15461243">{{cite journal |vauthors=Hultén P, Höjer J, Ludwigs U, Janson A|title=Hexafluorine vs. standard decontamination to reduce systemic toxicity after dermal exposure to hydrofluoric acid |journal=J. Toxicol. Clin. Toxicol. |volume=42 |issue=4 |pages=355–61 |year=2004 |pmid=15461243 |doi=10.1081/CLT-120039541}}</ref><ref>{{cite journal|title=News & Views|journal=Chemical Health and Safety |date=September–October 2005|volume= 12|issue=5|pages=35–37| doi = 10.1016/j.chs.2005.07.007 }}</ref> However, because it is absorbed, medical treatment is necessary;<ref name="RMTHFE">{{cite web|url=http://www51.honeywell.com/sm/hfacid/common/documents/HF_medical_book.pdf |title=Recommended Medical Treatment for Hydrofluoric Acid Exposure |accessdate=2009-05-06 |publisher=Honeywell Specialty Materials |url-status=dead |archiveurl=https://web.archive.org/web/20090325112238/http://www51.honeywell.com/sm/hfacid/common/documents/HF_medical_book.pdf |archivedate=March 25, 2009 }}</ref> rinsing off is not enough. Intra-arterial infusions of calcium chloride have also shown great effectiveness in treating burns.<ref>{{Cite journal|pmid=1567323 |title=Intra-arterial calcium infusion for hydrofluoric acid burns | volume=63|issue=3|date=March 1992|vauthors=Siegel DC, Heard JM|journal=Aviat Space Environ Med|pages=206–11}}</ref>
-Hydrogen fluoride is generated upon combustion of many fluorine-containing compounds such as products containing [[Viton]] and [[Polytetrafluoroethylene| polytetrafluoroethylene (Teflon)]] parts.<ref>{{cite journal|last=Koch|first=Ernst-Christian|title=Metal-Fluorocarbon-Pyrolants IV: Thermochemical and Combustion Behaviour of Magnesium/Teflon/Viton (MTV)| doi = 10.1002/prep.200290004 | journal = [[Propellants, Explosives, Pyrotechnics]] | volume = 27 | year = 2002 | pages = 340–351|issue=6}}</ref> [[Hydrofluorocarbon]]s in [[automatic fire suppression]] systems can release hydrogen fluoride at high temperatures, and this has led to deaths from acute [[respiratory failure]] in military personnel when a [[rocket-propelled grenade]] hit the fire suppression system in their vehicle.<ref name="HFC">{{cite web|url=https://www.sto.nato.int/publications/_layouts/WordViewer.aspx?id=/publications/STO%20Meeting%20Proceedings/RTO-MP-HFM-207/MP-HFM-207-03.doc&Source=https%3A%2F%2Fwww%2Esto%2Enato%2Eint%2Fpublications%2FSTO%2520Meeting%2520Proceedings%2FForms%2FAll%2520MPs%2Easpx%3FRootFolder%3D%252Fpublications%252FSTO%2520Meeting%2520Proceedings%252FRTO%252DMP%252DHFM%252D207%26FolderCTID%3D0x0120D5200078F9E87043356C409A0D30823AFA16F602008CF184CAB7588E468F5E9FA364E05BA5%26View%3D%257B72ED425F%2DC31F%2D451C%2DA545%2D41122BBA61A7%257D&DefaultItemOpen=1&DefaultItemOpen=1|title=Hydrogen Fluoride Inhalation Injury from a Fire Suppression System|author1=Chauviere, Matt|author2=Zierold, Dustin|date=2011-09-17|publisher=NATO|accessdate=2013-08-22}}</ref> Hydrofluoric acid can be released from volcanoes, sea salt aerosol, and from welding or manufacturing processes.<ref name=":0" />
+Hydrogen fluoride is generated upon combustion of many fluorine-containing compounds such as products containing [[Viton]] and [[Polytetrafluoroethylene| polytetrafluoroethylene (Teflon)]] parts.<ref>{{cite journal|last=Koch|first=Ernst-Christian|title=Metal-Fluorocarbon-Pyrolants IV: Thermochemical and Combustion Behaviour of Magnesium/Teflon/Viton (MTV)| doi = 10.1002/prep.200290004 | journal = [[Propellants, Explosives, Pyrotechnics]] | volume = 27 | year = 2002 | pages = 340–351|issue=6}}</ref> [[Hydrofluorocarbon]]s in [[automatic fire suppression]] systems can release hydrogen fluoride at high temperatures, and this has led to deaths from acute [[respiratory failure]] in military personnel when a [[rocket-propelled grenade]] hit the fire suppression system in their vehicle.<ref name="HFC" /> Hydrofluoric acid can be released from volcanoes, sea salt aerosol, and from welding or manufacturing processes.<ref name=":0" />
 {{clear}}
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 ==See also==
 *[[Vapour phase decomposition]]
 ==References==