| Revision as of 12:00, 12 May 2011 editCheMoBot (talk | contribs)Bots141,565 edits Updating {{chembox}} (no changed fields - added verified revid - updated 'UNII_Ref', 'ChemSpiderID_Ref', 'StdInChI_Ref', 'StdInChIKey_Ref', 'ChEMBL_Ref', 'KEGG_Ref') per Chem/Drugbox validation (← Previous edit |
Latest revision as of 01:11, 15 December 2023 edit undoSabrefencer9 (talk | contribs)126 editsm added a missing wordTag: Visual edit |
| (72 intermediate revisions by 36 users not shown) |
| Line 1: |
Line 1: |
|
{{chembox |
|
{{chembox |
|
|
| Verifiedfields = changed |
| ⚫ |
| verifiedrevid = 414406259 |
|
|
|
| Watchedfields = changed |
| ⚫ |
| Name = Phosphotungstic acid |
|
|
⚫ |
| verifiedrevid = 428739813 |
| ⚫ |
| ImageFile = Phosphotungstate-3D-polyhedra.png |
|
|
⚫ |
| Name = Phosphotungstic acid |
|
<!-- | ImageSize = 200px --> |
|
|
⚫ |
| ImageFile = Phosphotungstate-3D-polyhedra.png |
| ⚫ |
| ImageName = Structure of the phosphotungstate anion |
|
|
| OtherNames = Tungstophosphoric acid (TPA)<br>Phosphotungstic acid (PTA, PWA) |
|
| ImageFile1 = Phosphotungstic acid.ვკ.jpg |
|
⚫ |
| ImageName = Structure of the phosphotungstate anion |
|
12-Phosphotungstic acid<br>12-Tungstophosphoric acid<ref>Cotton, F. Albert; Wilkinson, Geoffrey (1966). Advanced Inorganic Chemistry (2nd Edn.). New York:Wiley.</ref><br>Dodecatungstophosphoric acid |
|
|
|
| OtherNames = Tungstophosphoric acid (TPA)<br>Phosphotungstic acid (PTA, PWA) |
| ⚫ |
| Section1 = {{Chembox Identifiers |
|
|
|
12-Phosphotungstic acid<br>12-Tungstophosphoric acid<ref>{{Cite book|title=Advanced inorganic chemistry: a comprehensive text|last1=Cotton|first1=Frank Albert|last2=Wilkinson|first2=Geoffrey | name-list-style = vanc |publisher=Wiley|year=1966|isbn=0470175583|edition=2nd|location=New York|lccn=66020662|oclc=85904497}}</ref><br>Dodecatungstophosphoric acid |
| ⚫ |
| CASNo = 1343-93-7 |
|
|
⚫ |
|Section1={{Chembox Identifiers |
| ⚫ |
| CASNo_Ref = {{cascite|correct|CAS}} |
|
|
⚫ |
| CASNo = 1343-93-7 |
|
| CASOther = <br/>12501-23-4 (hydrate) |
|
|
⚫ |
| CASNo_Ref = {{cascite|correct|CAS}} |
| ⚫ |
}} |
|
|
|
| CASNo2_Ref = {{cascite|changed|??}} |
| ⚫ |
| Section2 = {{Chembox Properties |
|
|
|
| CASNo2 = 12501-23-4 |
|
| Formula = H<sub>3</sub>PW<sub>12</sub>O<sub>40</sub> |
|
|
⚫ |
| index2_label = (hydrate) |
| ⚫ |
| MolarMass = 2880.2 g/mol (anhydrous) |
|
|
|
| ChemSpiderID = 21241328 |
| ⚫ |
| Density = |
|
|
|
| EC_number2 = 603-020-3 |
| ⚫ |
| Solvent = other solvents |
|
|
|
| PubChem2= 16212977 |
| ⚫ |
| SolubleOther = |
|
|
|
| UNII_Ref = {{fdacite|correct|FDA}} |
| ⚫ |
| MeltingPt = 89 °C (hydrate) |
|
|
|
| UNII = 5KAC2X78XM |
| ⚫ |
| BoilingPt = |
|
|
|
| InChI2=1S/H3O4P.H2O.36O.12W/c1-5(2,3)4;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;/h(H3,1,2,3,4);1H2;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;; |
| ⚫ |
}} |
|
|
|
| InChIKey2 = AVFBYUADVDVJQL-UHFFFAOYSA-N |
|
|
| SMILES = 18%21%24(O%16%18%23(O56(O1)(O247(O9%22(O%12%13(O2)(O3%11%14(O%17%19(O(O3)(O4)(O5)(67%15%2089%10(O(O(O%10)(O%11)(O%12)(%13%14%15))(O%16)(O%17)(%18%19%20))(O%21)(O%22)))(O%23))))(O%24)O))O))O |
|
⚫ |
}} |
|
⚫ |
|Section2={{Chembox Properties |
|
|
| Formula = {{chem2|H3}} |
|
⚫ |
| MolarMass = 2880.2 g/mol (anhydrous) |
|
⚫ |
| Density = |
|
⚫ |
| Solvent = other solvents |
|
⚫ |
| SolubleOther = |
|
|
| MeltingPtC = 89 |
|
|
| MeltingPt_notes = (hydrate) |
|
⚫ |
| BoilingPt = |
|
⚫ |
}} |
|
|
|Section7={{Chembox Hazards |
|
|
| GHSPictograms = {{GHS05}}{{GHS07}}{{GHS09}} |
|
|
| GHSSignalWord = Danger |
|
|
| HPhrases = {{H-phrases|302|314|411}} |
|
|
| PPhrases = {{P-phrases|260|264|270|273|280|301+312|301+330+331|303+361+353|304+340|305+351+338|310|321|330|363|391|405|501}} |
|
|
}} |
|
}} |
|
}} |
| ⚫ |
'''Phosphotungstic acid''' ('''PTA'''), '''tungstophosphoric acid''' ('''TPA'''), is a ] with the chemical formula {{Hydrogen}}<sub>3</sub>{{Phosphorus}}{{Tungsten}}<sub>12</sub>{{Oxygen}}<sub>40</sub>. It normally present as a hydrate. '''EPTA''' is the name of ]ic phosphotungstic acid, its alcohol solution used in biology. It has the appearance of small, colorless-grayish or slightly yellow-green crystals, with melting point 89 °C (24 H<sub>2</sub>O hydrate). It is odorless and soluble in water (200 g/100 ml). It is not especially toxic, but is a mild acidic irritant. The compound is known by a variety of different names and acronyms (see 'other names' section of infobox). |
|
|
|
|
|
|
⚫ |
'''Phosphotungstic acid''' ('''PTA''') or '''tungstophosphoric acid''' ('''TPA'''), is a ] with the chemical formula {{chem2|]3]]12]40]}}. It forms hydrates {{chem2|H3*''n''H2O}}. It is normally isolated as the ''n'' = 24 hydrate but can be ] to the hexahydrate (''n'' = 6).<ref name=Dias/> '''EPTA''' is the name of ]ic phosphotungstic acid, its alcohol solution used in biology. It has the appearance of small, colorless-grayish or slightly yellow-green crystals, with melting point 89 °C (24 {{chem2|H2O}} hydrate). It is odorless and soluble in water (200 g/100 ml). It is not especially toxic, but is a mild acidic irritant. The compound is known by a variety of names and acronyms (see 'other names' section of infobox). |
| ⚫ |
In these names the "12" or "dodeca" reflects the fact that the anion contains 12 tungsten atoms. Some early workers who did not know the structure, such as ],<ref name="Wu">''Contribution to the chemistry of phosphomolybdic acids, phosphotungstic acids and allied substances'' H Wu The ] 43, 1, (1920), 189</ref> called it phospho-24-tungstic acid, formulating it as 3H<sub>2</sub>O.P<sub>2</sub>O<sub>5</sub> 24WO<sub>3</sub>.59H<sub>2</sub>O, (P<sub>2</sub>W<sub>24</sub>O<sub>80</sub>H<sub>6</sub>).29H<sub>2</sub>O, which correctly identifies the atomic ratios of P, W and O. This formula was still quoted in papers as late as 1970.<ref name = quintarelli>''On phosphotungstic staining, I'' G Quintarelli, R Zito, J.A Cifonelli The ] 19, 11, (1971, 641</ref> |
|
|
|
|
|
⚫ |
In these names the "12" or "dodeca" reflects the fact that the anion contains 12 tungsten atoms. Some early workers who did not know the structure<ref name="Wu">{{Cite journal| vauthors = Hsein W |date=1920|title=Contribution to the chemistry of phosphomolybdic acids, phosphotungstic acids and allied substances|url=http://www.jbc.org/content/43/1/189.short|journal=Journal of Biological Chemistry|volume=43|pages=189–220 |doi=10.1016/S0021-9258(18)86325-6|doi-access=free}}</ref> called it phospho-24-tungstic acid, formulating it as 3H<sub>2</sub>O·P<sub>2</sub>O<sub>5</sub> 24WO<sub>3</sub>·59H<sub>2</sub>O<!--What the heck is this formula?! The compound formula with a white space, and hydrated first time with 3 water molecules and again with 59 water molecules?! Please help!-->, {{chem2|(P2W24O80H6)*29H2O}}, which correctly identifies the atomic ratios of P, W and O. This formula was still quoted in papers as late as 1970.<ref name = quintarelli>{{cite journal | vauthors = Quintarelli G, Zito R, Cifonelli JA | title = On phosphotungstic acid staining. I | journal = The Journal of Histochemistry and Cytochemistry | volume = 19 | issue = 11 | pages = 641–7 | date = November 1971 | pmid = 4107745 | doi = 10.1177/19.11.641 | doi-access = }}</ref> |
|
|
|
|
|
Phosphotungstic acid is used in ] as a component for ] of cell specimens, often together with ] as ]. It binds to ], ], and fibres of ]s, and replaces the anions of dyes from these materials, selectively decoloring them. |
|
Phosphotungstic acid is used in ] as a component for ] of cell specimens, often together with ] as ]. It binds to ], ], and fibres of ]s, and replaces the anions of dyes from these materials, selectively decoloring them. |
| Line 30: |
Line 50: |
|
Phosphotungstic acid is electron dense, opaque for ]s. It is a common ] for ]es, ]s, ]s, and other biological tissue materials for imaging by a ]. |
|
Phosphotungstic acid is electron dense, opaque for ]s. It is a common ] for ]es, ]s, ]s, and other biological tissue materials for imaging by a ]. |
|
|
|
|
|
==Structure== |
|
== Structure == |
|
] |
|
] |
|
Gouzerh<ref name = gouzerh>''From Scheele and Berzelius to Müller: polyoxometalates (POMs) revisited and the "missing link" between the bottom up and top down approaches'' P. Gouzerh, M. Che; ], 2006, 298, 9</ref> summarises the historical views on the structure of phosphotungstic acid leading up to Keggin's determination of the structure as: |
|
Gouzerh<ref>{{Cite journal| vauthors = Gouzerh P, Che M |date=2006|title=From Scheele and Berzelius to Müller Polyoxometalates (POMs) revisited and the "missing link" between the bottom up and top down approaches|journal=]|volume=298|pages=9–22|s2cid=42749543}}</ref> summarises the historical views on the structure of phosphotungstic acid leading up to Keggin's determination of the structure as: |
|
*H<sub>7</sub> proposed by Miolati and further developed by Rosenheim |
|
*{{chem2|H7}} proposed by Miolati and further developed by Rosenheim |
|
*H<sub>3</sub> (Pauling) |
|
*{{chem2|H3}} (Pauling) |
|
The structure was determined by J.F Keggin first published in 1933<ref>''Structure of the Molecule of 12-Phosphotungstic Acid'' J. F. Keggin, Nature 1933, 131, 908.</ref> and then in 1934<ref>''The Structure and Formula of 12-Phosphotungstic Acid'' J.F. Keggin. Proc. Roy. Soc., A, 144, 851, 75-100 (1934) {{doi|10.1098/rspa.1934.0035}}</ref> and is generally known as the ]. The anion has full tetrahedral symmetry and comprises a cage of twelve tungsten atoms linked by oxygen atoms with the phosphorus atom at its centre. The picture on the right shows the octahedral coordination of oxygen atoms around the tungsten atoms, and that the surface of the anion has both bridging and terminal oxygen atoms. Further investigation showed that the compound was a hexahydrate not a pentahydrate as Keggin had proposed.<ref>''Dodecatungstophosphoric acid hexahydrate, (H<sub>5</sub>O<sub>2</sub><sup>+</sup>)<sub>3</sub>(PW<sub>12</sub>O<sub>40</sub><sup>3<nowiki>−</nowiki></sup>). The true structure of Keggin's `pentahydrate' from single-crystal X-ray and neutron diffraction data'' Brown G.M., Noe-Spirlet M.-R., Busing W.R., Levy H.A., Acta Crystallogr., 1977, B33, 1038 {{doi|10.1107/S0567740877005330}}</ref> |
|
The structure was determined by J.F Keggin first published in 1933<ref>{{Cite journal| vauthors = Keggin JF |date=1933|title=Structure of the Molecule of 12-Phosphotungstic Acid|journal=Nature|volume=131|issue=3321|pages=908–909|doi=10.1038/131908b0|s2cid=4122733|issn=0028-0836}}</ref> and then in 1934<ref>{{Cite journal| vauthors = Keggin JF |date=1934|title=The structure and formula of 12-phosphotungstic acid|journal= ]|language=en|volume=144|issue=851|pages=75–100|doi=10.1098/rspa.1934.0035|issn=0950-1207|bibcode=1934RSPSA.144...75K|doi-access=}}</ref> and is generally known as the ]. The anion has full tetrahedral symmetry and comprises a cage of twelve tungsten atoms linked by oxygen atoms with the phosphorus atom at its centre. The picture on the right shows the octahedral coordination of oxygen atoms around the tungsten atoms, and that the surface of the anion has both bridging and terminal oxygen atoms. Further investigation showed that the compound was a hexahydrate not a pentahydrate as Keggin had proposed.<ref>{{Cite journal | vauthors = Brown GM, Noe-Spirlet MR, Busing WR, Levy HA |date=1977|title=Dodecatungstophosphoric acid hexahydrate, (H<sub>5</sub>O<sub>2</sub><sup>+</sup>)<sub>3</sub>(PW<sub>12</sub>O<sub>40</sub><sup>3−</sup>). The true structure of Keggin's 'pentahydrate' from single-crystal X-ray and neutron diffraction data|journal= ]|volume=33|issue=4|pages=1038–1046|doi=10.1107/s0567740877005330|issn=0567-7408|doi-access=}}</ref> |
|
|
|
|
|
==Preparation and chemical properties== |
|
==Preparation and chemical properties== |
|
Phosphotungstic acid can be prepared by the reaction of ], Na<sub>2</sub>WO<sub>4</sub>.2H<sub>2</sub>O, with ], H<sub>3</sub>PO<sub>4</sub>, acidified with ], HCl.<ref name = Wu /> |
|
Phosphotungstic acid can be prepared by the reaction of ] dihydrate, {{chem2|Na2WO4*2H2O}}, with ], {{chem2|H3PO4}}, acidified with ], HCl.<ref>{{cite book|chapter=Phosphotungstic Acid|first1=John C.|last1=Bailar, Jr.|first2=H. S.|last2=Booth|first3=M.|last3=Grennert|title=Inorganic Syntheses|volume=1|pages=132–133|year=1939|doi=10.1002/9780470132326.ch49|isbn=9780470132326}}</ref> This procedure has been updated.<ref name=Dias>{{cite book |series=Inorganic Syntheses|first1=J. A.|last1=Dias|first2=S. C. L.|last2=Dias|first3=E.|last3=Caliman|title=Keggin Structure Polyoxoometalates|chapter=Keggin Structure Polyoxometalates|volume=36|page=210-217|year=2014|doi=10.1002/9781118744994.ch39|isbn=9781118744994}}</ref> |
|
|
|
|
|
Phosphotungstic acid solutions decompose as the pH is increased. A step-wise decomposition has been determined and the approximate compositions at various pH values are as follows:<ref name = zhu>''A study of the decomposition behaviour of 12-tungstophosphate heteropolyacid in solution'' Zhu Z., Tain R., Rhodes C. ], 81,10, 1, (2003) , 1044-1050</ref> |
|
Phosphotungstic acid solutions decompose as the pH is increased. A step-wise decomposition has been determined and the approximate compositions at various pH values are as follows:<ref name = zhu>{{Cite journal | vauthors = Zhu Z, Tain R, Rhodes C |date=2003|title=A study of the decomposition behaviour of 12-tungstophosphate heteropolyacid in solution|journal=]|volume=81|issue=10|pages=1044–1050|doi=10.1139/v03-129 }}</ref> |
|
|
|
|
|
:{|class="wikitable" |
|
:{|class="wikitable" |
| Line 46: |
Line 66: |
|
! pH !! principal components |
|
! pH !! principal components |
|
|- |
|
|- |
|
|
| 1.0 ||{{chem2|(3-)}} |
|
| 1.0 || <sup>3<nowiki>−</nowiki></sup> |
|
|
|- |
|
|- |
|
|
| 2.2 ||{{chem2|(3-)}}, {{chem2|(6-)}}, {{chem2|(7-)}} |
|
| 2.2 || <sup>3<nowiki>−</nowiki></sup>, <sup>6<nowiki>−</nowiki></sup>, <sup>7<nowiki>−</nowiki></sup> |
|
|
|- |
|
|- |
|
|
| 3.5 ||{{chem2|(3-)}}, {{chem2|(6-)}}, {{chem2|(7-)}}, {{chem2|(6-)}}, {{chem2|(10-)}} |
|
| 3.5 ||<sup>3<nowiki>−</nowiki></sup>, <sup>6<nowiki>−</nowiki></sup>, <sup>7<nowiki>−</nowiki></sup>, <sup>6<nowiki>−</nowiki></sup>, <sup>10<nowiki>−</nowiki> |
|
|
</sup> |
|
|
|- |
|
|- |
|
|
| 5.4 ||{{chem2|(6-)}}, {{chem2|(7-)}}, {{chem2|(6-)}} |
|
| 5.4 ||<sup>6<nowiki>−</nowiki></sup>, <sup>7<nowiki>−</nowiki></sup>, <sup>6<nowiki>−</nowiki></sup> |
|
|
|- |
|
|- |
|
|
| 7.3 ||{{chem2|(9-)}} |
|
| 7.3 ||<sup>9<nowiki>−</nowiki></sup> |
|
|
|- |
|
|- |
|
|
| 8.3 ||{{chem2|PO4(3-)}}, {{chem2|WO4(2-)}} |
|
| 8.3 ||PO<sub>4</sub><sup>3<nowiki>−</nowiki></sup>, WO<sub>4</sub><sup>2<nowiki>−</nowiki></sup> |
|
|
|} |
|
|} |
|
|
|
|
|
The species <sup>7<nowiki>−</nowiki></sup> is a lacunary, or defective Keggin ion. The <sup>6<nowiki>−</nowiki></sup> has a ]. At pH less than 8, the presence of ethanol or acetone stabilises the anion, <sup>3<nowiki>−</nowiki></sup>, reducing decomposition.<ref name = zhu /> |
|
The species {{chem2|(7-)}} is a lacunary, or defective Keggin ion. The {{chem2|(6-)}} has a ]. At pH less than 8, the presence of ethanol or acetone stabilises the anion, {{chem2|(3-)}}, reducing decomposition.<ref name = zhu /> |
|
|
|
|
|
Tungstophosphoric acid is thermally stable up to 400°C, and is more stable than the analogous ], H<sub>4</sub>SiW<sub>12</sub>O<sub>40</sub>.<ref name = okuharaencyclo>''Oxide catalysts in solid state chemistry'' T Okuhara, M Misono Encyclopedia of Inorganic chemistry Editor R Bruce King (1994) John Wiley and Sons ISBN 0-471-93620-0</ref> |
|
Tungstophosphoric acid is thermally stable up to 400 °C, and is more stable than the analogous ], {{chem2|H4}}.<ref name = okuharaencyclo>''Oxide catalysts in solid state chemistry'' T Okuhara, M Misono Encyclopedia of Inorganic chemistry Editor R Bruce King (1994) John Wiley and Sons {{ISBN|0-471-93620-0}}</ref> |
|
|
|
|
|
Large quantities of polar molecules such as pyridine are absorbed into the bulk phase and not simply on the surface. Solid state ] studies of ] absorbed in the bulk phase show that both protonated dimers, ((C<sub>2</sub>H<sub>5</sub>OH)<sub>2</sub>H<sup>+</sup>) and monomers, (C<sub>2</sub>H<sub>5</sub>OH<sub>2</sub><sup>+</sup>) are present. |
|
Large quantities of polar molecules such as ] are absorbed into the bulk phase and not simply adsorbed onto the surface. Solid state ] studies of ] absorbed in the bulk phase show that both protonated dimers, {{chem2|(C2H5OH)2H+}}, and monomers, {{chem2|C2H5OH2+}}, are present. |
|
|
|
|
|
Phosphotungstic acid is less sensitive to reduction than phosphomolybdic acid. Reduction with ] or ] produces a brown coloured compound. the related silicotungstic acid when reduced forms a similar brown compound where one of the four W3 units in the Keggin structure becomes a metal-metal bonded cluster of three edge shared W(IV) octahedra.<ref>''Polyoxoanions'' M.T.Pope, Encyclopedia of Inorganic Chemistry Editor R Bruce King (1994) John Wiley and Sons ISBN 0-471-93620-0</ref> |
|
Phosphotungstic acid is less sensitive to reduction than phosphomolybdic acid. Reduction with ] or ] produces a brown coloured compound. the related silicotungstic acid when reduced forms a similar brown compound where one of the four {{chem2|W3}} units in the Keggin structure becomes a metal-metal bonded cluster of three edge shared {{chem2|W^{IV}|}} octahedra.<ref>''Polyoxoanions'' M.T.Pope, Encyclopedia of Inorganic Chemistry Editor R Bruce King (1994) John Wiley and Sons {{ISBN|0-471-93620-0}}</ref> |
|
|
|
|
|
Phosphotungstic acid is the strongest of ]s. Its conjugate base is the PW<sub>12</sub>O<sub>40</sub><sup>3−</sup> anion.<ref>, Davis Group, Department of Chemical Engineering, University of Virginia. Retrieved 2009-06-02.</ref> Its acidity in acetic acid has been investigated and shows that the three protons dissociate independently rather than sequentially, and the acid sites are of the same strength.<ref>Acidity measurements on a heteropolyacid hydrate in acetic acid solution : a case of three hydrons ionizing independently, rather than consecutively Farcasiu D. ; Jing Qi Li ; ], 152, 1, 198-203</ref> One estimate of the acidity is that the solid has an acidity stronger than ] =<nowiki>−</nowiki>13.16,<ref name = okuharaencyclo /> which would qualify the compound as a ]. This acidic strength means that even at low pH the acid is fully dissociated. |
|
Phosphotungstic acid is the strongest of ]s. Its conjugate base is the {{chem2|(3−)}} anion.<ref> {{Webarchive|url=https://web.archive.org/web/20110811035823/http://www.people.virginia.edu/~davis/acid%20catalysis.htm |date=2011-08-11 }}, Davis Group, Department of Chemical Engineering, University of Virginia. Retrieved 2009-06-02.</ref> Its acidity in acetic acid has been investigated and shows that the three protons dissociate independently rather than sequentially, and the acid sites are of the same strength.<ref>{{Cite journal | vauthors = Farcasiu D, Li JQ | title = Acidity measurements on a heteropolyacid hydrate in acetic acid solution: a case of three hydrons ionizing independently, rather than consecutively. | journal = Journal of Catalysis | date = March 1995 | volume = 152 | issue = 1 | pages = 198–203 | doi = 10.1006/jcat.1995.1073}}</ref> One estimate of the acidity is that the solid has an acidity stronger than ] = −13.16,<ref name = okuharaencyclo /> which would qualify the compound as a ]. This acidic strength means that even at low pH the acid is fully dissociated. |
|
|
|
|
|
==Uses== |
|
==Uses== |
|
|
|
|
===Catalyst=== |
|
===Catalyst=== |
|
In common with the other ]s phosphotungstic acid is a catalyst and its high acidity and thermal stability make it a catalyst of choice according to some researchers.<ref>''Zirconia-supported 12-tungstophosphoric acid as a solid catalyst for the synthesis of linear alkyl benzenes''Biju M. Devassy, F. Lefebvre and S.B. Halligudi, Journal of Catalysis 231,1,(2005),1-10 {{doi|10.1016/j.jcat.2004.09.024}}</ref> It is in solution as a ], and as a ] "supported" on a substrate e.g. ], ]. Some acid catalysed reactions include: |
|
In common with the other ]s phosphotungstic acid is a catalyst and its high acidity and thermal stability make it a catalyst of choice according to some researchers.<ref>{{Cite journal| vauthors = Devassy BM, Lefebvre F, Halligudi SG |date=2005|title=Zirconia-supported 12-tungstophosphoric acid as a solid catalyst for the synthesis of linear alkyl benzenes|journal=]|volume=231|issue=1|pages=1–10|doi=10.1016/j.jcat.2004.09.024|issn=0021-9517}}</ref> It is in solution as a ], and as a ] "supported" on a substrate e.g. ], ]. Some acid catalysed reactions include: |
|
*the ] of the hydrolysis of propene to give 2-propanol |
|
*the ] of the hydrolysis of propene to give 2-propanol |
|
*the ] of the ] |
|
*the ] of the ] |
|
*the ] of the dehydration of 2-propanol to propene and ] to hydrocarbons. |
|
*the ] of the dehydration of 2-propanol to propene and ] to hydrocarbons. |
|
|
|
|
|
===Dyeing and pigments=== |
|
===Dyeing and pigments=== |
|
Phosphotungstic acid has been used to precipitate different types of dyes as "]".<ref>'' Non-staining pigments and their use'' US patent: 2999026 Issue date: Sep 1961, Inventor: Chester Davis</ref> Examples are basic dyes and triphenylmethane dyes, e.g. ] derivatives.<ref>''Pigments, Organic'' K Hunger, W Herbst Ullmans Encyclopedia of Industrial Chemistry</ref> |
|
Phosphotungstic acid has been used to precipitate different types of dyes as "]".<ref>'''' US patent: 2999026 Issue date: Sep 1961, Inventor: Chester Davis</ref> Examples are basic dyes and triphenylmethane dyes, e.g. ] derivatives.<ref>{{Cite book|title=Ullmann's encyclopedia of industrial chemistry | vauthors = Hunger K, Herbst W |publisher=Wiley InterScience|year=2000|isbn=9783527306732| veditors = Bohnet M |edition=6|location=Weinheim, Germany|chapter=Pigments, Organic|doi=10.1002/14356007.a20_371|oclc=751968805}}</ref> |
|
|
|
|
|
===Histology=== |
|
===Histology=== |
|
Phosphotungstic acid is used in ] for staining specimens, as a component of phosphotungstic acid haematoxylin, ], and “trichrome” reagents, and as a ] for imaging by a ]. |
|
Phosphotungstic acid is used in ] for staining specimens, as a component of phosphotungstic acid haematoxylin, ], and “trichrome” reagents, and as a ] for imaging by a ].{{citation needed|date=February 2021}} |
|
|
|
|
|
;Phosphotungstic acid haematoxylin (]) |
|
;Phosphotungstic acid haematoxylin (]) |
|
|
|
|
|
:Mallory described the reagent now generally known as PTAH in 1897.<ref>''On certain improvements in histological technique: I. A differential stain for amoeligbæ coli. II. phosphotungstic-acid-hæmatoxylin stain for certain tissue elements. III. A method of fixation for neuroglia fibres.'' F. B. Mallory J. Exp. Med., 2, 5, (1897) 529-533</ref> PTAH stains tissues either reddish brown or blue depending on their type. This property of simultaneously staining two different colours is different from other haematoxylin reagents e.g. alum-haematoxylin. The role of phosphotungstic acid and the mechanism of staining is not fully understood. Interestingly the active component of haematoxylin is the oxidised form, haematin, although this rarely acknowledged in the literature which refer to haematoxylin staining. Phosphotungstic acid forms a lake with haematin.<ref>''Phosphotungstic acid- hematoxylin; spectrophotometry of the lake in solution and in stained tissue'' Terner JY, Gurland J, Gaer F. Stain Technol (1964),39, 141-53</ref> The make –up of the reagent is uncertain, examination of a year old sample showed there to be three coloured components, blue, red and yellow.<ref>''On the mechanism of Mallory's phosphotungstic acid - haematoxylin stain'' Puchtler H, Waldrop FS, Meloan S.N. J Microsc 1980, 119, 3, 383</ref> These were not identified. Some investigations of “model” systems, reacting various compounds such as ]s, ]s, ]s and ]s with PTAH show that they give rise to different colours.<ref>''Phosphotungstic acid-hematoxylin. Reactivity in vitro'' J. Y. Terner Journal of Histochemistry and Cytochemistry, 1966, 4, 345</ref> |
|
:Mallory described the reagent now generally known as PTAH in 1897.<ref>{{cite journal | vauthors = Mallory FB | title = On certain improvements in histological technique: I. A differential stain for amoeligbæ coli. II. phosphotungstic-acid-hæmatoxylin stain for certain tissue elements. III. A method of fixation for neuroglia fibres | journal = The Journal of Experimental Medicine | volume = 2 | issue = 5 | pages = 529–33 | date = September 1897 | pmid = 19866848 | pmc = 2132861 | doi = 10.1084/jem.2.5.529 }}</ref> PTAH stains tissues either reddish brown or blue depending on their type. This property of simultaneously staining two different colours is different from other haematoxylin reagents e.g. alum-haematoxylin. The role of phosphotungstic acid and the mechanism of staining is not fully understood. The active component of haematoxylin is the oxidised form, haematin, although this rarely acknowledged in the literature which refer to haematoxylin staining. Phosphotungstic acid forms a lake with haematin.<ref>{{cite journal | vauthors = Terner JY, Gurland J, Gaer F | title = Phosphotungstic acid-hematoxylin; spectrophotometry of the lake in solution and in stained tissue | journal = Stain Technology | volume = 39 | issue = 3 | pages = 141–53 | date = May 1964 | pmid = 14157455 | doi = 10.3109/10520296409061220 }}</ref> The make –up of the reagent is uncertain, examination of a year old sample showed there to be three coloured components, blue, red and yellow.<ref>{{Cite journal | vauthors = Puchtler H, Waldrop FS, Meloan SN |date=1980|title=On the mechanism of Mallory's phosphotungstic acid-haematoxylin stain|journal=]|volume=119|issue=3|pages=383–390|doi=10.1111/j.1365-2818.1980.tb04109.x|pmid=6157822|s2cid=3148787|issn=0022-2720}}</ref> These were not identified. Some investigations of “model” systems, reacting various compounds such as ]s, ]s, ]s and ]s with PTAH show that they give rise to different colours.<ref>{{cite journal | vauthors = Terner JY | title = Phosphotungstic acid-hematoxylin, reactivity in vitro | journal = The Journal of Histochemistry and Cytochemistry | volume = 14 | issue = 4 | pages = 345–51 | date = April 1966 | pmid = 4164215 | doi = 10.1177/14.4.345 | doi-access = free }}</ref> |
|
|
|
|
|
;Trichrome reagents |
|
;Trichrome reagents |
|
:In these reagents two or three basic dyes are used with phosphotungstic acid, in either a one step or multi-stage procedure. These reagents colour different tissue types different colours. Again the mechanism of staining is not fully understood. Some explanations include the proposal that phosphotungstic acid acts as a ] to bind the dye to the tissue<ref>''Dyes and other colorants in microtechnique and biomedical research'' J A Kiernan Color. Technol. 122, 1–21 {{doi|10.1111/j.1478-4408.2006.00009.x}}</ref> or that alternatively it binds to tissue blocking it to dye molecules.<ref>''The role of phosphotungstic and phosphomolybdic acids in connective tissue staining I. Histochemical studies'' M.M. Everett and W.A. Miller ], 6, 1, (1974), 25-34 , {{doi|10.1007/BF01011535}}</ref> |
|
:In these reagents two or three basic dyes are used with phosphotungstic acid, in either a one step or multi-stage procedure. These reagents colour different tissue types different colours. Again the mechanism of staining is not fully understood. Some explanations include the proposal that phosphotungstic acid acts as a ] to bind the dye to the tissue<ref>{{Cite journal| vauthors = Kiernan JA |date=2006|title=Dyes and other colorants in microtechnique and biomedical research|journal=Coloration Technology|volume=122|issue=1|pages=1–21|doi=10.1111/j.1478-4408.2006.00009.x|issn=1472-3581|doi-access=free}}</ref> or that alternatively it binds to tissue blocking it to dye molecules.<ref>{{Cite journal | vauthors = Everett MM, Miller WA | date=1974|title=The role of phosphotungstic and phosphomolybdic acids in connective tissue staining I. Histochemical studies|journal= The Histochemical Journal|volume=6|issue=1|pages=25–34|doi=10.1007/bf01011535 | pmid=4130630| s2cid=27429820}}</ref> |
|
|
|
|
|
;Negative staining |
|
;Negative staining |
| Line 94: |
Line 114: |
|
|
|
|
|
===Analysis=== |
|
===Analysis=== |
|
The potassium salt is only slightly soluble, unlike most other phosphotungstate salts, and has been proposed as a method for the ] of potassium.<ref>''Gravimetric determination of potassium as phospho-12-tungstate'' W.K. Rieben, D.D. Van Slyke, Journal of Biological Chemistry, 156, (1944), 2, 765</ref> |
|
The potassium salt is only slightly soluble, unlike most other phosphotungstate salts, and has been proposed as a method for the ] of potassium.<ref>{{Cite journal | vauthors = Rieben WK, Van Slyke DD | title = Gravimetric determination of potassium as phospho-12-tungstate. | journal = Journal of Biological Chemistry | date = 1944 | volume = 156 | issue = 2 | pages = 765–76 | doi = 10.1016/S0021-9258(18)51159-5 | url = http://www.jbc.org/content/156/2/765.citation | doi-access = free }}</ref> |
|
|
|
|
|
===Precipitation of proteins=== |
|
===Precipitation of proteins=== |
|
In a number of analytical procedures one of the roles of phosphotungstic acid is to precipitate out proteins. It has been termed a "universal" precipitant for polar proteins.<ref>''Phosphotungstate: a" universal" (nonspecific) precipitant for polar polymers in acid solution'' JE Scott - Journal of Histochemistry and Cytochemistry, 197119, 11, 689</ref> Further studies showed that no precipitation occurred with α-amino groups but did occur with guanidino, ε-amino and imidazole groups.<ref>''Precipitation of proteins: The separation of proteins with heteropolyacids M. Z. Sternberg, Biotechnology and Bioengineering 12, 1, (1970), 1 - 17</ref> |
|
In a number of analytical procedures one of the roles of phosphotungstic acid is to precipitate out proteins. It has been termed a "universal" precipitant for polar proteins.<ref>{{cite journal | vauthors = Scott JE | title = Phosphotungstate: a "universal" (nonspecific) precipitant for polar polymers in acid solution | journal = The Journal of Histochemistry and Cytochemistry | volume = 19 | issue = 11 | pages = 689–91 | date = November 1971 | pmid = 5121870 | doi = 10.1177/19.11.689 | doi-access = free }}</ref> Further studies showed that no precipitation occurred with α-amino groups but did occur with guanidino, ε-amino and imidazole groups.<ref>{{cite journal | vauthors = Sternberg MZ | title = The separation of proteins with heteropolyacids | journal = Biotechnology and Bioengineering | volume = 12 | issue = 1 | pages = 1–17 | date = January 1970 | pmid = 5433882 | doi = 10.1002/bit.260120102 | s2cid = 27459070 }}</ref> |
|
|
|
|
|
===Medicinal=== |
|
===Medicinal=== |
|
Very little work appears to have been carried out in this area. One example relates to liver necrosis in rats.<ref>''Protective effects of tungstophosphoric acid and sodium tungstate on chemically induced liver necrosis in Wistar rats'' Snežana Uskoković-Marković1, Marina Milenković, Aleksandra Topić, Jelena Kotur-Stevuljević, Aleksandra Stefanović, Jelena Antić-Stanković, J Pharm Pharmaceut Sci 10 (3): 340-349, 2007</ref> |
|
Very little work appears to have been carried out in this area. One example relates to liver necrosis in rats.<ref>{{cite journal | vauthors = Uskoković-Marković S, Milenković M, Topić A, Kotur-Stevuljević J, Stefanović A, Antić-Stanković J | title = Protective effects of tungstophosphoric acid and sodium tungstate on chemically induced liver necrosis in wistar rats | journal = Journal of Pharmacy & Pharmaceutical Sciences | volume = 10 | issue = 3 | pages = 340–9 | date = 2007 | pmid = 17727797 }}</ref> |
|
|
|
|
|
===Composite proton exchange membranes=== |
|
===Composite proton exchange membranes=== |
|
The heteropoly acids, including phosphotungstic acid, are being investigated as materials in composite ]s, such as ]. The interest lies in the potential of these composite materials in the manufacture of fuel cells as they have improved operating characteristics.<ref>''Composite membranes for medium temperature PEM fuel cells'' G. Alberti and M. Casciola Annual Review of Materials Research 33, (2003), 129-154 {{doi|10.1146/annurev.matsci.33.022702.154702}}</ref> |
|
The heteropoly acids, including phosphotungstic acid, are being investigated as materials in composite ]s, such as ]. The interest lies in the potential of these composite materials in the manufacture of fuel cells as they have improved operating characteristics.<ref>{{Cite journal | vauthors = Alberti G, Casciola M |date=2003|title=Composite Membranes for Medium-Temperature PEM Fuel Cells|journal=]|volume=33|issue=1|pages=129–154|doi=10.1146/annurev.matsci.33.022702.154702|issn=1531-7331|bibcode=2003AnRMS..33..129A}}</ref> |
|
|
|
|
|
==See also== |
|
== See also == |
|
* ] |
|
* ] |
|
|
|
|
|
==References== |
|
== References == |
|
{{reflist|2}} |
|
{{reflist|30em}} |
|
|
|
|
|
{{Tungsten compounds}} |
|
{{Tungsten compounds}} |
|
|
|
|
|
] |
|
] |
|
] |
|
] |
|
] |
|
] |
|
] |
|
] |
|
] |
|
] |
|
] |
|
] |
|
] |
|
] |
|
|
|
|
] |
|
|
] |
|
|
] |
|