Wikipedia:WikiProject Chemicals/Chembox validation/VerifiedDataSandbox and Hexafluorosilicic acid: Difference between pages
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Saving copy of the {{chembox}} taken from revid 473304766 of page Hexafluorosilicic_acid for the Chem/Drugbox validation project (updated: ''). |
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{{short description|Octahedric silicon compound}} |
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{{ambox | text = This page contains a copy of the infobox ({{tl|chembox}}) taken from revid [{{fullurl:Hexafluorosilicic_acid|oldid=473304766}} 473304766] of page [[Hexafluorosilicic_acid]] with values updated to verified values.}} |
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{{redirect|Fluorosilicate|Fluorosilicate glass and glass-ceramics|Fluorosilicate glass}} |
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{{Chembox |
{{Chembox |
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| Watchedfields = changed |
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| verifiedrevid = 439462824 |
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| verifiedrevid = 477003251 |
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| ImageFile=Hexafluorosilicic acid molecular structure.png |
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| ImageFile2= |
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| PIN = Hexafluorosilicic acid |
| PIN = Hexafluorosilicic acid |
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| SystematicName = Dihydrogen hexafluorosilicate |
| SystematicName = Dihydrogen hexafluorosilicate |
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| OtherNames = Fluorosilicic acid, |
| OtherNames = Fluorosilicic acid, fluosilic acid, hydrofluorosilicic acid, silicofluoride, silicofluoric acid, oxonium hexafluorosilanediuide, oxonium hexafluoridosilicate(2−) |
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|Section1={{Chembox Identifiers |
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| CASNo = 16961-83-4 |
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| CASNo_Ref = {{cascite|correct|CAS}} |
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| UNII_Ref = {{fdacite|correct|FDA}} |
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| PubChem = 21863527 |
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| UNII = 53V4OQG6U1 |
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| PubChem_Ref = {{Pubchemcite|correct|PubChem}} |
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| PubChem = 21863527 |
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| ChemSpiderID = 17215660 |
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| ChemSpiderID = 17215660 |
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| ChemSpiderID_Ref = {{chemspidercite|correct|chemspider}} |
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| ChemSpiderID_Ref = {{chemspidercite|correct|chemspider}} |
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| EINECS = 241-034-8 |
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| EINECS = 241-034-8 |
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| UNNumber = 1778 |
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| SMILES = [H+].[H+].F[Si-2](F)(F)(F)(F)F |
| RTECS = VV8225000 |
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| SMILES = [H+].[H+].F[Si-2](F)(F)(F)(F)F |
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| SMILES1 = [H+].[H+].F[Si--](F)(F)(F)(F)F |
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| StdInChI_Ref = {{stdinchicite|correct|chemspider}} |
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| StdInChI = 1S/F6Si/c1-7(2,3,4,5)6/q-2/p+2 |
| StdInChI = 1S/F6Si/c1-7(2,3,4,5)6/q-2/p+2 |
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| InChI = 1/F6Si/c1-7(2,3,4,5)6/q-2/p+2 |
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| StdInChIKey_Ref = {{stdinchicite|correct|chemspider}} |
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| StdInChIKey = OHORFAFFMDIQRR-UHFFFAOYSA-P |
| StdInChIKey = OHORFAFFMDIQRR-UHFFFAOYSA-P |
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| InChIKey = OHORFAFFMDIQRR-SKRXCDHZAM}} |
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|Section2={{Chembox Properties |
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| H=2 | Si=1 | F=6 |
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| Appearance = transparent, colorless, fuming liquid |
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| F = 6 |
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| Odor = sour, pungent |
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| Density = 1.22 g/cm<sup>3</sup> (25% soln.)<br/>1.38 g/cm<sup>3</sup> (35% soln.)<br/>1.46 g/cm<sup>3</sup> (61% soln.) |
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| ExactMass = 143.982995827 g mol<sup>-1</sup> |
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| MeltingPt = {{circa}} {{convert|19|C|F K}} {{nowrap|(60–70% solution)}}<br/>< {{convert|-30|C|F K}} {{nowrap|(35% solution)}} |
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| Density = 1.22 g/cm<sup>3</sup> (25% soln.)<br/>1.38 g/cm<sup>3</sup> (35% soln.)<br/>1.46 g/cm<sup>3</sup> (61% soln.) |
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| BoilingPtC = 108.5 |
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| MeltingPt = ca. 19 °C (60–70% soln.)<br/><−30 °C (35& soln.)}} |
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| BoilingPt_notes = (decomposes) |
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| Section3 = {{Chembox Structure |
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| Solubility = miscible |
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| MolShape = Octahedral SiF<sub>6</sub><sup>2<nowiki>−</nowiki></sup> |
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| RefractIndex = 1.3465 |
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| pKa = 1.92<ref name=P82db>{{cite book|title=Ionisation Constants of Inorganic Acids and Bases in Aqueous Solution|editor-first=D. D.|editor-last=Perrin|edition=2<sup>nd</sup>|series=[[IUPAC]] Chemical Data|issue=29|publisher=Pergamon|location=Oxford|year=1982|publication-date=1984|orig-date=1969|lccn=82-16524|isbn=0-08-029214-3|at=Entry 91}}</ref> |
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}} |
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|Section3={{Chembox Structure |
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| MolShape = Octahedral SiF<sub>6</sub><sup>2<nowiki>−</nowiki></sup> |
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}} |
}} |
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|Section7={{Chembox Hazards |
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| NFPA-H = 3 |
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| ExternalMSDS = [http://ptcl.chem.ox.ac.uk/MSDS/DI/dihydrogen_hexafluorosilicate.html External MSDS] |
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| NFPA-F = 0 |
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| EUIndex = 009-011-00-5 |
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| NFPA-R = 0 |
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| EUClass = Corrosive ('''C''') |
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| NFPA-S = |
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| ExternalSDS = [https://www.sigmaaldrich.com/US/en/sds/sial/01302 External MSDS] |
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| SPhrases = {{S1/2}}, {{S26}}, {{S27}}, {{S45}} |
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| GHSPictograms = {{GHS05}} |
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| FlashPt = Non-flammable |
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| GHSSignalWord = Danger |
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| HPhrases = {{H-phrases|314}} |
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| PPhrases = {{P-phrases|260|264|280|301+330+331|303+361+353|304+340|305+351+338|310|321|363|405|501}} |
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| FlashPt = Non-flammable |
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| LD50 = 430 mg/kg (oral, rat) |
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}} |
}} |
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|Section8={{Chembox Related |
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| OtherCations = [[Ammonium hexafluorosilicate]]<br /> |
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[[Sodium fluorosilicate]] |
[[Sodium fluorosilicate]] |
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| OtherAnions = [[Hexafluorotitanic acid]]<br />[[Hexafluorozirconic acid]] |
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| OtherCompounds = [[Hexafluorophosphoric acid]]<br/>[[Fluoroboric acid]]}} |
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}} |
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'''Hexafluorosilicic acid''' is an [[inorganic compound]] with the [[chemical formula]] {{Chem|H|2|SiF|6}}. Aqueous solutions of hexafluorosilicic acid consist of salts of the cation and hexafluorosilicate anion. These salts and their aqueous solutions are colorless. |
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Hexafluorosilicic acid is produced naturally on a large scale in volcanoes.<ref name="Palache">Palache, C., Berman, H., and Frondel, C. (1951) Dana’s System of Mineralogy, Volume II: Halides, Nitrates, Borates, Carbonates, Sulfates, Phosphates, Arsenates, Tungstates, Molybdates, etc. John Wiley and Sons, Inc., New York, 7th edition.</ref><ref name="Anthony">Anthony, J.W., Bideaux, R.A., Bladh, K.W., and Nichols, M.C. (1997) Handbook of Mineralogy, Volume III: Halides, Hydroxides, Oxides. Mineral Data Publishing, Tucson. |
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*[https://www.handbookofmineralogy.org/pdfs/bararite.pdf Bararite] |
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*[https://www.handbookofmineralogy.org/pdfs/cryptohalite.pdf Cryptohalite]</ref> It is manufactured as a coproduct in the production of [[phosphate fertilizer]]s. The resulting hexafluorosilicic acid is almost exclusively consumed as a precursor to [[aluminum trifluoride]] and [[sodium hexafluoroaluminate|synthetic cryolite]], which are used in aluminium processing. Salts derived from hexafluorosilicic acid are called '''hexafluorosilicates'''. |
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== Structure == |
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[[File:(H5O2)2SiF6, ICSDcode 40388full.png|thumb|left|Structure of (H<sub>5</sub>O<sub>2</sub>)<sub>2</sub>SiF<sub>6</sub>. The hydrogen bonding between the fluoride and protons are indicated by dashed lines. Color code: green = F, orange = Si, red = O, gray = H.<ref name=ZAAC>{{cite journal |doi=10.1002/zaac.19885590103|title=The Crystalline Hydrates of Hexafluorosilicic Acid: A Combined Phase-Analytical and Structural Study |year=1988 |last1=Mootz |first1=D. |last2=Oellers |first2=E.-J. |journal=Zeitschrift für anorganische und allgemeine Chemie |volume=559 |pages=27–39 }}</ref>]] |
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Hexafluorosilicic acid has been crystallized as various hydrates. These include ([[Hydronium#Zundel cation|H<sub>5</sub>O<sub>2</sub>]])<sub>2</sub>SiF<sub>6</sub>, the more complicated (H<sub>5</sub>O<sub>2</sub>)<sub>2</sub>SiF<sub>6</sub>·2H<sub>2</sub>O, and (H<sub>5</sub>O<sub>2</sub>)(H<sub>7</sub>O<sub>3</sub>)SiF<sub>6</sub>·4.5H<sub>2</sub>O. In all of these salts, the octahedral hexafluorosilicate anion is [[hydrogen bond]]ed to the cations.<ref name=ZAAC/> |
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Aqueous solutions of hexafluorosilicic acid are often described as {{Chem|H|2|SiF|6}}. |
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==Production and principal reactions== |
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Hexafluorosilicic acid is produced commercially from fluoride-containing minerals that also contain silicates. Specifically, [[apatite]] and [[fluorapatite]] are treated with [[sulfuric acid]] to give [[phosphoric acid]], a precursor to several water-soluble fertilizers. This is called the [[Phosphoric acid#Wet process|wet phosphoric acid process]].<ref name=USGS>USGS. [http://minerals.usgs.gov/minerals/pubs/commodity/fluorspar/fluormcs07.pdf Fluorspar].</ref> As a by-product, approximately 50 kg of hexafluorosilicic acid is produced per tonne of HF owing to reactions involving silica-containing mineral impurities.<ref name= NTP >{{Cite web| url=https://ntp.niehs.nih.gov/ntp/htdocs/chem_background/exsumpdf/fluorosilicates_508.pdf| title=Sodium Hexafluorosilicate [CASRN 16893-85-9] and Fluorosilicic Acid [CASRN 16961-83-4] Review of Toxicological Literature| website=National Toxicology Program (U.S.)| access-date=13 July 2017| url-status=live| archive-url=https://web.archive.org/web/20121022152457/http://ntp.niehs.nih.gov/ntp/htdocs/Chem_Background/ExSumPDF/Fluorosilicates.pdf| archive-date=22 October 2012}}</ref>{{rp|p=3}} |
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Some of the [[hydrogen fluoride]] (HF) produced during this process in turn reacts with [[silicon dioxide]] (SiO<sub>2</sub>) impurities, which are unavoidable constituents of the mineral feedstock, to give [[silicon tetrafluoride]]. Thus formed, the silicon tetrafluoride reacts further with HF.{{Citation needed|date=May 2022}} The net process can be described as:<ref name="Ullmann">{{Ullmann|first1=J. |last1=Aigueperse |first2=P. |last2=Mollard |first3=D. |last3=Devilliers |first4=M. |last4=Chemla |first5=R. |last5=Faron |first6=R. |last6=Romano |first7=J. P. |last7=Cuer |title=Fluorine Compounds, Inorganic |date=2005 |doi=10.1002/14356007.a11_307}}</ref>{{Page needed|date=May 2022}} |
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:{{chem2|6 HF + SiO2 → SiF6(2-) + 2 H3O+}} |
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Hexafluorosilicic acid can also be produced by treating silicon tetrafluoride with hydrofluoric acid.<ref name=Ullmann/> |
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== Reactions == |
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Hexafluorosilic acid is only stable in [[hydrogen fluoride]] or acidic aqueous solutions. In any other circumstance, it acts as a source of [[hydrofluoric acid]]. Thus, for example, hexafluorosilicic acid pure or in [[oleum]] solution evolves [[silicon tetrafluoride]] until the residual hydrogen fluoride re-establishes equilibrium:<ref name=Ullmann/> |
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:H<sub>2</sub>SiF<sub>6</sub> {{eqm}} 2 HF(''l'') + SiF<sub>4</sub>(''g'') |
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In alkaline-to-neutral aqueous solutions, hexafluorosilicic acid readily hydrolyzes to fluoride anions and amorphous, [[hydrated silica]] ("SiO<sub>2</sub>"). Strong bases give fluorosilicate salts at first, but any [[limiting reactant|stoichiometric excess]] begins hydrolysis.<ref name=Ullmann/> At the concentrations usually used for water fluoridation, 99% hydrolysis occurs:{{r|NTP}}<ref>{{cite journal|last2=Wilson|first2=Erin|last3=Callender|first3=Andrew|last4=Morris|first4=Michael D.|last5=Beck|first5=Larry W.|year=2006|title=Reexamination of Hexafluorosilicate Hydrolysis by <sup>19</sup>F NMR and pH Measurement|journal=Environ. Sci. Technol.|volume=40|issue=8|pages=2572–2577|doi=10.1021/es052295s|last1=Finney|first1=William F.|pmid=16683594|bibcode=2006EnST...40.2572F}}</ref> |
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:{{Chem|SiF|6|2-}} + 2 H<sub>2</sub>O → 6 F<sup>−</sup> + SiO<sub>2</sub> + 4 H<sup>+</sup> |
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=== Alkali and alkaline earth salts === |
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Neutralization of solutions of hexafluorosilicic acid with [[alkali metal]] bases produces the corresponding alkali metal fluorosilicate salts: |
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:H<sub>2</sub>SiF<sub>6</sub> + 2 NaOH → Na<sub>2</sub>SiF<sub>6</sub> + 2 H<sub>2</sub>O |
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The resulting salt Na<sub>2</sub>SiF<sub>6</sub> is mainly used in water fluoridation. Related ammonium and barium salts are produced similarly for other applications. At room temperature 15-30% concentrated hexafluorosilicic acid undergoes similar reactions with [[chloride]]s, [[hydroxide]]s, and [[carbonate]]s of alkali and [[alkaline earth metal]]s.<ref name=":2">{{cite book |title=Silicon Tetrafluoride |year=1953 |series=Inorganic Syntheses |volume=4 |pages=147–8 |doi=10.1002/9780470132357.ch47 |vauthors=Hoffman CJ, Gutowsky HS, Schumb WC, Breck DW}}</ref> |
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[[Sodium hexafluorosilicate]] for instance may be produced by treating [[sodium chloride]] ({{chem2|NaCl}}) by hexafluorosilicic acid:{{r|NTP|p=3}}<ref name=":1">{{Cite patent|country=Us|number=A345458|title=Patent Silicon tetrafluoride generation|status=Granted|pubdate=January 3, 1982|gdate=1982|invent1=Keith|invent2=L. Yaws|inventor1-first=C. Hansen|inventor2-first=Carl}}</ref>{{rp|7}} |
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: {{chem2|2NaCl + H2SiF6}} {{overset|27 °C|→}} {{chem2|Na2SiF6↓ + 2 HCl}} |
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: {{chem2|BaCl2 + H2SiF6}} {{overset|27 °C|→}} {{chem2|BaSiF6↓ + 2 HCl}} |
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Heating [[sodium hexafluorosilicate]] gives [[silicon tetrafluoride]]:{{R|name=:1|page=8}} |
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:{{chem2|Na2SiF6}} {{overset|>400 °C|→}} {{chem2|SiF4 + 2 NaF}} |
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== Uses == |
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The majority of the hexafluorosilicic acid is converted to [[aluminium fluoride]] and [[Sodium hexafluoroaluminate|synthetic cryolite]]. These materials are central to the conversion of aluminium ore into [[aluminium]] metal. The conversion to aluminium trifluoride is described as:<ref name=Ullmann/> |
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:H<sub>2</sub>SiF<sub>6</sub> + Al<sub>2</sub>O<sub>3</sub> → 2 AlF<sub>3</sub> + SiO<sub>2</sub> + H<sub>2</sub>O |
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Hexafluorosilicic acid is also converted to a variety of useful hexafluorosilicate salts. The potassium salt, [[Potassium fluorosilicate]], is used in the production of porcelains, the magnesium salt for hardened concretes and as an insecticide, and the barium salts for phosphors. |
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Hexafluorosilicic acid and the salts are used as [[wood preservation]] agents.<ref>{{cite journal |author=Carsten Mai, [[Holger Militz]] |year=2004 |title=Modification of wood with silicon compounds. inorganic silicon compounds and sol-gel systems: a review |journal=Wood Science and Technology |volume=37 |issue=5 |page=339 |doi=10.1007/s00226-003-0205-5 |s2cid=9672269}}</ref> |
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=== Lead refining === |
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Hexafluorosilicic acid is also used as an electrolyte in the [[Betts electrolytic process]] for refining lead. |
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=== Rust removers === |
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Hexafluorosilicic acid (identified as hydrofluorosilicic acid on the label) along with [[oxalic acid]] are the active ingredients used in ''Iron Out'' rust-removing cleaning products, which are essentially varieties of [[laundry sour]]. |
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===Niche applications=== |
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H<sub>2</sub>SiF<sub>6</sub> is a specialized [[reagent]] in [[organic synthesis]] for cleaving Si–O bonds of [[silyl ether]]s. It is more reactive for this purpose than HF. It reacts faster with ''t''-[[Silyl ether|butyldimethysilyl]] ([[TBDMS]]) ethers than [[Silyl ether|triisopropylsilyl]] ([[Silyl ether|TIPS]]) ethers.<ref>{{cite book|last1=Pilcher|first1= A. S. |last2=DeShong |first2=P. |chapter=Fluorosilicic Acid |title=Encyclopedia of Reagents for Organic Synthesis|date=2001 |publisher=John Wiley & Sons |doi=10.1002/047084289X.rf013|isbn= 0471936235 }}</ref> |
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=== Treating concrete === |
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The application of hexafluorosilica acid to a calcium rich surface such as concrete will give that surface some resistance to acid attack.<ref>Properties of Concrete by A M Neville</ref> |
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:CaCO<sub>3</sub> + H<sub>2</sub>O → Ca<sup>2+</sup> + 2 OH<sup>−</sup> + CO<sub>2</sub> |
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:H<sub>2</sub>SiF<sub>6</sub> → 2 H<sup>+</sup> + {{Chem|SiF|6|2-}} |
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:{{Chem|SiF|6|2-}} + 2 H<sub>2</sub>O → 6 F<sup>−</sup> + SiO<sub>2</sub> + 4 H<sup>+</sup> |
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: Ca<sup>2+</sup> + 2 F<sup>−</sup> → CaF<sub>2</sub> |
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[[Calcium fluoride]] (CaF<sub>2</sub>) is an insoluble solid that is acid resistant. |
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==Natural salts== |
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Some rare minerals, encountered either within volcanic or coal-fire fumaroles, are salts of the hexafluorosilicic acid. Examples include [[Ammonium fluorosilicate|ammonium hexafluorosilicate]] that naturally occurs as two polymorphs: cryptohalite and [[bararite]].<ref name="Cryptohalite, Mindat">{{Cite web|url=https://www.mindat.org/min-1163.html|title=Cryptohalite}}</ref><ref name="Bararite, Mindat">{{Cite web|url=https://www.mindat.org/min-511.html|title = Bararite}}</ref><ref name="Kuszewski et al. 2020">{{cite journal | doi=10.1016/j.scitotenv.2019.134274 | title=Carbon‑nitrogen compounds, alcohols, mercaptans, monoterpenes, acetates, aldehydes, ketones, SF6, PH3, and other fire gases in coal-mining waste heaps of Upper Silesian Coal Basin (Poland) – a re-investigation by means of in situ FTIR external database approach | year=2020 | last1=Kruszewski | first1=Łukasz | last2=Fabiańska | first2=Monika J. | last3=Segit | first3=Tomasz | last4=Kusy | first4=Danuta | last5=Motyliński | first5=Rafał | last6=Ciesielczuk | first6=Justyna | last7=Deput | first7=Ewa | journal=Science of the Total Environment | volume=698 | page=134274 | pmid=31509784 | bibcode=2020ScTEn.698m4274K | s2cid=202563638 }}</ref> |
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==Safety== |
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Hexafluorosilicic acid can release [[hydrogen fluoride]] (HF) when evaporated, so it has similar risks. Inhalation of the vapors may cause [[lung edema]]. Like hydrogen fluoride, it attacks glass and [[stoneware]].<ref>{{cite web |url=http://niosh.dnacih.com/nioshdbs/ipcsneng/neng1233.htm |title=Fluorosilicic Acid – International Chemical Safety Cards |website=NIOSH |access-date=2015-03-10}}</ref> The [[Median lethal dose|LD<sub>50</sub>]] value of hexafluorosilicic acid is 430 mg/kg.{{r|NTP}} |
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==See also== |
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* [[Ammonium fluorosilicate]] |
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* [[Sodium fluorosilicate]] |
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* [[Potassium fluorosilicate]] |
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==References== |
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{{Reflist|30em}} |
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{{Hydrogen compounds}} |
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[[Category:Mineral acids]] |
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[[Category:Hydrogen compounds]] |
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[[Category:Nonmetal halides]] |
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[[Category:Hexafluorosilicates]] |
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[[Category:Fluoro complexes]] |