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>Facts707: (orthophosphoric acid, monophosphoric acid or phosphoric(V) acid),

2022-01-12T22:55:38Z

(orthophosphoric acid, monophosphoric acid or phosphoric(V) acid),

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{{Short description|Chemical compound}}
{{About|orthophosphoric acid|other acids commonly called "phosphoric acid"|Phosphoric acids and phosphates}}
{{Distinguish | Phosphorous acid}}
{{Use dmy dates|date=January 2020}}
{{chembox|Verifiedfields=changed|Watchedfields=changed|verifiedrevid=470622096|Name=|ImageFile=Phosphoric-acid-2D-dimensions.png|ImageSize=150px|ImageName=Structural formula of phosphoric acid, showing dimensions|ImageFileL1=Phosphoric-acid-3D-balls.png|ImageSizeL1=120px|ImageNameL1=Ball-and-stick model|ImageFileR1=Phosphoric-acid-3D-vdW.png|ImageSizeR1=120px|ImageNameR1=Space-filling model|IUPACName=Phosphoric acid|OtherNames=Orthophosphoric acid|SystematicName=|Section1={{Chembox Identifiers
| PubChem = 1004
| UNII_Ref = {{fdacite|correct|FDA}}
| UNII = E4GA8884NN
| KEGG_Ref = {{keggcite|correct|kegg}}
| KEGG = D05467
| InChI = 1/H3O4P/c1-5(2,3)4/h(H3,1,2,3,4)
| InChIKey = NBIIXXVUZAFLBC-UHFFFAOYAI
| ChEBI_Ref = {{ebicite|correct|EBI}}
| ChEBI = 26078
| SMILES = OP(=O)(O)O
| ChEMBL_Ref = {{ebicite|correct|EBI}}
| ChEMBL = 1187
| StdInChI_Ref = {{stdinchicite|correct|chemspider}}
| StdInChI = 1S/H3O4P/c1-5(2,3)4/h(H3,1,2,3,4)
| StdInChIKey_Ref = {{stdinchicite|correct|chemspider}}
| StdInChIKey = NBIIXXVUZAFLBC-UHFFFAOYSA-N
| CASNo = 7664-38-2
| CASNo_Ref = {{cascite|correct|CAS}}
| ChemSpiderID_Ref = {{chemspidercite|correct|chemspider}}
| ChemSpiderID = 979
| EINECS = 231-633-2
| UNNumber = 1805
| RTECS = TB6300000
}}|Section2={{Chembox Properties
| Formula = {{Chem|H|3|PO|4}}
| H=3 | P=1 | O=4
| Appearance = white solid
| Odor = Odorless
| Density = 1.6845 {{nbsp}}g⋅cm−3 (25 °C, 85%),<ref name="Density 85%">
{{Cite journal
| author=Christensen, J. H.
| author2=Reed, R. B.
| name-list-style=amp
| year=1955
| title=Design and Analysis Data—Density of Aqueous Solutions of Phosphoric Acid Measurements at 25 °C.
| journal=Ind. Eng. Chem.
| volume=47 | issue=6 | pages=1277–1280
| doi=10.1021/ie50546a061
}}</ref> 1.834 {{nbsp}}g⋅cm−3 (solid)<ref name="Density solid">{{Cite web
| url=https://cameochemicals.noaa.gov/chemical/4231
| title=CAMEO Chemicals Datasheet – Phosphoric Acid
| access-date=15 August 2019
| archive-date=15 August 2019
| archive-url=https://web.archive.org/web/20190815155917/https://cameochemicals.noaa.gov/chemical/4231
| url-status=live
}}</ref>
| MeltingPtC = 40–42.4
| MeltingPt_ref = <ref name=crc>Haynes, p. 4.80</ref>
| BoilingPt = {{ubl
| 212 °C (414 °F)<ref name=chemspider>{{cite web |url=http://www.chemspider.com/Chemical-Structure.979.html |title=Phosphoric acid |website=www.chemspider.com |access-date=3 March 2020 |archive-date=12 March 2020 |archive-url=https://web.archive.org/web/20200312003851/http://www.chemspider.com/Chemical-Structure.979.html |url-status=live }}</ref> (only water evaporates)<ref>{{Cite journal|url=https://pubs.acs.org/doi/pdf/10.1021/ie50507a050|doi=10.1021/ie50507a050|title=Vapor Pressure of Phosphoric Acids|year=1952|last1=Brown|first1=Earl H.|last2=Whitt|first2=Carlton D.|journal=Industrial & Engineering Chemistry|volume=44|issue=3|pages=615–618}}</ref>
}}
| Solubility = {{ubl
| 392.2{{nbsp}}g/100{{nnbsp}}g (−16.3 °C)
| 369.4{{nbsp}}g/100{{nnbsp}}mL (0.5 °C)
| 446{{nbsp}}g/100{{nnbsp}}mL (15 °C)<ref name=sioc>{{cite book
| last1 = Seidell
| first1 = Atherton
| last2 = Linke
| first2 = William F.
| year = 1952
| title = Solubilities of Inorganic and Organic Compounds
| publisher = Van Nostrand
| url = https://books.google.com/books?id=k2e5AAAAIAAJ
| access-date = 2 June 2014
| archive-date = 11 March 2020
| archive-url = https://web.archive.org/web/20200311230632/https://books.google.com/books?id=k2e5AAAAIAAJ
| url-status = live
}}</ref>
| 548{{nbsp}}g/100{{nnbsp}}mL (20 °C)<ref name=crc/>
}}
| SolubleOther = Soluble in [[ethanol]]
| pKa = {{ubl
| p''K''a1 = 2.16<ref>Haynes, p. 5.92</ref>
| p''K''a2 = 7.20
| p''K''a3 = 12.32
}}
| ConjugateBase = [[Dihydrogen phosphate]]
| Viscosity = 2.4–9.4{{nbsp}}[[poise (unit)|cP]] (85% {{abbr|aq. soln.|aqueous solution}}) 147{{nbsp}}cP (100%)
| RefractIndex = {{ubl
| 1.3420 (8.8% w/w {{abbr|aq. soln.|aqueous solution}})<ref name="Refractive Index">
{{Cite journal
| author=Edwards, O. W.
| author2=Dunn, R. L.
| author3=Hatfield, J. D.
| name-list-style=amp
| year=1964
| title=Refractive Index of Phosphoric Acid Solutions at 25 C.
| journal=J. Chem. Eng. Data
| volume=9 | issue=4 | pages=508–509
| doi=10.1021/je60023a010
}}</ref>
| 1.4320 (85% aq. soln) 25 °C
}}
| VaporPressure = 0.03{{nbsp}}mmHg (20{{nbsp}}°C)<ref name=PGCH/>
| MagSus = −43.8·10−6{{nbsp}}cm3/mol<ref>Haynes, p. 4.134</ref>
| LogP = −2.15<ref name="chemsrc">{{Cite web
| url=https://www.chemsrc.com/en/cas/7664-38-2_329226.html
| title=phosphoric acid_msds
| access-date=2 May 2018
| archive-date=4 July 2017
| archive-url=https://web.archive.org/web/20170704022858/http://www.chemsrc.com/en/cas/7664-38-2_329226.html
| url-status=live
}}</ref>
}}|Section3={{Chembox Structure
| CrystalStruct = Monoclinic
| MolShape = Tetrahedral
}}|Section4={{Chembox Thermochemistry
| Thermochemistry_ref=<ref>Haynes, p. 5.13</ref>
| DeltaHf = −1271.7 kJ/mol
| DeltaGfree = -1123.6 kJ/mol
| Entropy = 150.8 J/mol⋅K
| HeatCapacity =145.0 J/mol⋅K
}}|Section5=|Section6=|Section7={{Chembox Hazards
| GHSPictograms = {{GHS05}}<ref name="sigma">{{Sigma-Aldrich|id=466123|name=Phosphoric acid|access-date=9 May 2014}}</ref>
| GHSSignalWord = Danger
| HPhrases = {{H-phrases|290|314}}<ref name="sigma" />
| PPhrases = {{P-phrases|280|305+351+338|310}}<ref name="sigma" />
| ExternalSDS = [http://www.inchem.org/documents/icsc/icsc/eics1008.htm ICSC 1008]
| NFPA-H = 3
| NFPA-R = 0
| NFPA-F = 0
| NFPA-S =
| FlashPt = Non-flammable
| LD50 = 1530{{nbsp}}mg/kg (rat, oral)<ref>{{IDLH|7664382|Phosphoric acid}}</ref>
| IDLH = 1000{{nbsp}}mg/m3<ref name=PGCH>{{PGCH|0506}}</ref>
| REL = TWA 1{{nbsp}}mg/m3 ST 3{{nbsp}}mg/m3<ref name=PGCH/>
| PEL = TWA 1{{nbsp}}mg/m3<ref name=PGCH/>
}}|Section8={{Chembox Related
| OtherFunction = {{ubl
| [[Hypophosphorous acid]]
| [[Phosphorous acid]]
| [[Pyrophosphoric acid]]
| [[Triphosphoric acid]]
| [[Peroxomonophosphoric acid]]
| [[Peroxodiphosphoric acid]]
}}
| OtherFunction_label = [[phosphorus]] [[oxoacid]]s
}}
}}

'''Phosphoric acid''' (orthophosphoric acid, monophosphoric acid or phosphoric(V) acid), is a [[weak acid]] with the [[chemical formula]] {{chem|[[Hydrogen|H]]|3|[[phosphorus|P]]|[[oxygen|O]]|4}}. The pure compound is a colorless [[solid]].

All three hydrogens are [[acid]]ic to varying degrees and can be lost from the [[molecule]] as H+ ions ([[protons]]). When all three H+ ions are removed, the result is an [[phosphate|orthophosphate]] ion PO43−, commonly called "phosphate". Removal of one or two protons gives [[phosphate|dihydrogen phosphate]] ion {{chem|H|2|PO|4|−}}, and the [[phosphate|hydrogen phosphate]] ion {{chem|HPO|4|2−}}, respectively. Orthophosphoric acid also forms [[esters]], called [[organophosphate]]s.<ref name="Westheimer">{{Cite journal|last=Westheimer |first=F.H. |author-link=Frank Westheimer |title=Why nature chose phosphates |journal=[[Science (journal)|Science]] |volume=235 |issue=4793 |pages=1173–1178 (see pp. 1175–1176) |date=6 June 1987 |doi=10.1126/science.2434996 |bibcode=1987Sci...235.1173W|citeseerx=10.1.1.462.3441 |pmid=2434996 }}</ref>

Phosphoric acid is commonly encountered in chemical laboratories as an 85% [[aqueous solution]], which is a colourless, odourless, and non-[[volatility (chemistry)|volatile]] syrupy liquid. Although phosphoric acid does not meet the strict definition of a [[strong acid]], the 85% solution can still severely irritate the skin and damage the eyes.

The name "orthophosphoric acid" can be used to distinguish this specific acid from other "[[phosphoric acids and phosphates|phosphoric acids]]", such as [[pyrophosphoric acid]]. Nevertheless, the term "phosphoric acid" often means this specific compound; and that is the current [[IUPAC nomenclature]].

==Manufacture==
Phosphoric acid is produced industrially by two general routes.<ref>{{cite book |last1=Becker |first1=Pierre |title=Phosphates and phosphoric acid |date=1988 |publisher=Marcel Dekker |location=New York |isbn=978-0824717124}}</ref> In the wet process a phosphate-containing mineral such as calcium [[hydroxyapatite]] is treated with [[sulfuric acid]].<ref>{{Greenwood&Earnshaw2nd|pages=520–522}}</ref>
: <chem>Ca5(PO4)3OH + 5H2SO4 -> 3H3PO4 + 5CaSO4v + H2O</chem>
[[Fluoroapatite]] is an alternative feedstock, in which case fluoride is removed as the insoluble compound Na2SiF6. The phosphoric acid solution usually contains 23–33% P2O5 (32–46% H3PO4). It may be concentrated to produce ''commercial-'' or ''merchant-grade'' phosphoric acid, which contains about 54–62% [[P2O5|P2O5]] (75–85% H3PO4). Further removal of water yields ''superphosphoric acid'' with a P2O5 concentration above 70% (corresponding to nearly 100% H3PO4). [[Calcium sulfate]] (gypsum) is produced as a by-product and is removed as [[phosphogypsum]].

To produce food-grade phosphoric acid, phosphate ore is first reduced with [[Coke (fuel)|coke]] in an [[electric arc furnace]], to make elemental [[phosphorus]]. Silica is also added, resulting in the production of [[calcium silicate]] slag. Elemental phosphorus is distilled out of the furnace and burned with air to produce high-purity [[phosphorus pentoxide]], which is dissolved in water to make phosphoric acid.

The phosphoric acid from both processes may be further purified by removing compounds of arsenic and other potentially toxic impurities.

==Acidic properties==
All three hydrogens are acidic, with dissociation constants p''K''a1 = 2.14, p''K''a2 = 7.20, and p''K''a3 = 12.37. It follows that, in water solutions, phosphoric acid is mostly dissociated into some combination of its three anions, except at very low [[pH]].
The equilibrium equations are:
:H3PO4   + H2O {{eqm}} H3O+ + H2PO4−      ''K''a1= 7.25×10−3 [p''K''a1 = 2.14]
:H2PO4−+ H2O {{eqm}} H3O+ + HPO42−       ''K''a2= 6.31×10−8 [p''K''a2 = 7.20]
:HPO42−+ H2O {{eqm}} H3O+ +  PO43−        ''K''a3= 3.98×10−13 [p''K''a3 = 12.37]

==Uses==
The dominant use of phosphoric acid is for [[fertilizer]]s, consuming approximately 90% of production.<ref name=Ullmann>{{Ullmann|first1=Klaus|last1=Schrödter|first2=Gerhard|last2=Bettermann|first3=Thomas |last3=Staffel|first4=Friedrich|last4=Wahl|first5=Thomas|last5=Klein|first6=Thomas|last6=Hofmann|title=Phosphoric Acid and Phosphates|year=2008|doi=10.1002/14356007.a19_465.pub3}}</ref>
{| class="wikitable"
|-
! Application
! Demand (2006) in thousands of tons
! Main phosphate derivatives
|-
| Soaps and detergents || 1836 || [[Sodium triphosphate|STPP]]
|-
| Food industry || 309 || [[Sodium triphosphate|STPP]] (Na5P3O10), [[Sodium hexametaphosphate|SHMP]], [[Trisodium phosphate|TSP]], [[Disodium pyrophosphate|SAPP]], [[Sodium aluminium phosphate|SAlP]], [[Monocalcium phosphate|MCP]], [[Disodium phosphate|DSP]] (Na2HPO4), H3PO4
|-
| [[Water treatment]] || 164 || SHMP, [[Sodium triphosphate|STPP]], [[Tetrasodium pyrophosphate|TSPP]], [[Monosodium phosphate|MSP]] (NaH2PO4), DSP
|-
| [[Toothpaste]]s || 68 || [[Dicalcium phosphate|DCP]] (CaHPO4), IMP, SMFP
|-
| Other applications || 287 || [[Sodium triphosphate|STPP]] (Na3P3O9), TCP, APP, DAP, [[zinc phosphate]] (Zn3(PO4)2), [[aluminium phosphate]] (AlPO4, H3PO4)
|}

Food-grade phosphoric acid (additive [[E number|E338]]<ref name=fgovuk>{{cite web|url=http://www.food.gov.uk/policy-advice/additivesbranch/enumberlist#h_7|title=Current EU approved additives and their E Numbers|date=14 March 2012|publisher=Foods Standards Agency|access-date=22 July 2012|archive-date=19 July 2013|archive-url=https://www.webcitation.org/6IDaVXq1n?url=http://www.food.gov.uk/policy-advice/additivesbranch/enumberlist#h_7|url-status=live}}</ref>) is used to acidify foods and beverages such as various [[cola]]s and jams, providing a tangy or sour taste. The phosphoric acid also serves as a [[preservative]].<ref>{{Cite web|title=Why is phosphoric acid used in some Coca‑Cola drinks?{{!}} Frequently Asked Questions {{!}} Coca-Cola GB|url=https://www.coca-cola.co.uk/our-business/faqs/why-is-phosphoric-acid-used-in-coca-cola-drinks-diet-coke-coke-zero|access-date=2021-08-31|website=www.coca-cola.co.uk|language=en-GB|archive-date=2 August 2021|archive-url=https://web.archive.org/web/20210802114054/https://www.coca-cola.co.uk/our-business/faqs/why-is-phosphoric-acid-used-in-coca-cola-drinks-diet-coke-coke-zero|url-status=live}}</ref> Soft drinks containing phosphoric acid, which would include [[Coca-Cola]], are sometimes called [[phosphate soda]]s or phosphates. Phosphoric acid in soft drinks has the potential to cause dental erosion.<ref>{{Cite journal|title=Dietary advice in dental practice|journal=British Dental Journal|volume=193|issue=10|pages=563–568|date=23 November 2002|doi=10.1038/sj.bdj.4801628|pmid=12481178|last1=Moynihan|first1=P. J.|doi-access=free}}</ref> Phosphoric acid also has the potential to contribute to the formation of [[Kidney stone disease|kidney stones]], especially in those who have had kidney stones previously.<ref name=Qa2014>{{cite journal |last1= Qaseem |first1= A |last2= Dallas |first2= P |last3= Forciea |first3= MA |last4= Starkey |first4= M |last5= Denberg |first5= TD |display-authors= 4 |title= Dietary and pharmacologic management to prevent recurrent nephrolithiasis in adults: A clinical practice guideline from the American College of Physicians |journal= [[Annals of Internal Medicine]] |date= 4 November 2014 |volume= 161 |issue= 9 |pages= 659–67 |doi= 10.7326/M13-2908 |pmid=25364887|doi-access= free }}</ref>

Specific applications of phosphoric acid include:
* in anti-rust treatment by [[phosphate conversion coating]] or [[Passivation (chemistry)|passivation]]
** to prevent [[iron]] [[oxidation]] by means of the [[Parkerization (metallurgy)|Parkerization]] process
* as an external standard for [[phosphorus-31 nuclear magnetic resonance]]
* in [[phosphoric acid fuel cell]]s
* in [[activated carbon]] production<ref>{{Cite journal | last1 = Toles | first1 = C. | last2 = Rimmer | first2 = S. | last3 = Hower | first3 = J. C. | doi = 10.1016/S0008-6223(96)00093-0 | title = Production of activated carbons from a washington lignite using phosphoric acid activation | journal = Carbon | volume = 34 | issue = 11 | pages = 1419 | year = 1996 }}</ref>
* in [[compound semiconductor]] processing, to etch [[Indium gallium arsenide]] selectively with respect to [[indium phosphide]]<ref>[http://terpconnect.umd.edu/~browns/wetetch.html Wet chemical etching.] {{Webarchive|url=https://web.archive.org/web/20120925075407/http://terpconnect.umd.edu/~browns/wetetch.html |date=25 September 2012 }} umd.edu.</ref>
* in [[microfabrication]] to etch [[silicon nitride]] selectively with respect to [[silicon dioxide]]<ref name="Wolf">{{cite book |title =Silicon processing for the VLSI era: Volume 1 – Process technology |last = Wolf |first = S. |author2=R. N. Tauber |year=1986 |page=534 |isbn=978-0-9616721-6-4}}</ref>
* as a pH adjuster in cosmetics and skin-care products<ref>{{cite web|publisher = Paula's Choice|title = Ingredient dictionary: P|work = Cosmetic ingredient dictionary|access-date = 16 November 2007|url = http://www.cosmeticscop.com/learn/cosmetic_dictionary.asp?id=21&letter=P|url-status = dead|archive-url = https://web.archive.org/web/20080118084632/http://www.cosmeticscop.com/learn/cosmetic_dictionary.asp?id=21&letter=P|archive-date = 18 January 2008|df = dmy-all}}</ref>
* as a sanitizing agent in the dairy, food, and brewing industries<ref>{{cite web|url=http://www.fivestarchemicals.com/wp-content/uploads/StarSanTech-HB2.pdf|title=STAR SAN|publisher=Five Star Chemicals|access-date=17 August 2015|archive-date=8 February 2016|archive-url=https://web.archive.org/web/20160208134008/http://www.fivestarchemicals.com/wp-content/uploads/StarSanTech-HB2.pdf|url-status=live}}</ref>

== Safety ==
A link has been shown between long-term regular cola intake and [[osteoporosis]] in later middle age in women (but not men).<ref>{{cite journal|vauthors=Tucker KL, Morita K, Qiao N, Hannan MT, Cupples LA, Kiel DP | title=Colas, but not other carbonated beverages, are associated with low bone mineral density in older women: The Framingham Osteoporosis Study| journal=American Journal of Clinical Nutrition| volume=84| pages=936–942| issue = 4| date = 1 October 2006| pmid = 17023723 | doi=10.1093/ajcn/84.4.936| doi-access=free}}</ref>

At moderate concentrations phosphoric acid solutions are irritating to the skin. Contact with concentrated solutions can cause severe skin burns and permanent eye damage.<ref name=":0">{{Cite web|url=http://www.sigmaaldrich.com/MSDS/MSDS/DisplayMSDSPage.do?country=US&language=en&productNumber=345245&brand=ALDRICH&PageToGoToURL=http%3A%2F%2Fwww.sigmaaldrich.com%2Fcatalog%2Fproduct%2Faldrich%2F345245%3Flang%3Den|title=Phosphoric Acid, 85 wt.% SDS|date=5 May 2016|website=Sigma-Aldrich|access-date=16 January 2017|archive-date=18 January 2017|archive-url=https://web.archive.org/web/20170118123759/http://www.sigmaaldrich.com/MSDS/MSDS/DisplayMSDSPage.do?country=US&language=en&productNumber=345245&brand=ALDRICH&PageToGoToURL=http%3A%2F%2Fwww.sigmaaldrich.com%2Fcatalog%2Fproduct%2Faldrich%2F345245%3Flang%3Den|url-status=live}}</ref>

==See also==
* Phosphate [[fertilizer]]s, such as [[ammonium phosphate]] fertilizers

==References==
{{Reflist|30em}}

==Cited sources==
*{{cite book | editor= Haynes, William M. | year = 2011 | title = CRC Handbook of Chemistry and Physics | edition = 92nd | publisher = [[CRC Press]] | isbn = 978-1439855119| title-link = CRC Handbook of Chemistry and Physics }}

==External links==
{{Commons category|Phosphoric acid|lcfirst=yes}}
* [http://www.npi.gov.au/substances/phosphoric-acid/index.html National pollutant inventory – Phosphoric acid fact sheet]
* [https://www.cdc.gov/niosh/npg/npgd0506.html NIOSH Pocket guide to chemical hazards]

{{Authority control}}

{{DEFAULTSORT:Phosphoric Acid}}
[[Category:Mineral acids]]
[[Category:Flavors]]
[[Category:Food acidity regulators]]
[[Category:Glassforming liquids and melts]]
[[Category:Phosphates]]
[[Category:Phosphorus oxoacids]]
[[Category:Hydrogen compounds]]
[[Category:Acid catalysts]]
[[Category:E-number additives]]
[[Category:Phosphorus(V) compounds]]

Phosphoric acid - Revision history

Sudeep 68899: basic expand citations for consistency and updated info

UpdateBot: robot: Update article (please report if you notice any mistake or error in this edit)

>Facts707: (orthophosphoric acid, monophosphoric acid or phosphoric(V) acid),