Tungstic Acid

100 Per Day

5-7 Days

500 Per Week

4 Hours

Crystal

Phosphotungstic acid can be prepared by the reaction of sodium tungstate, Na2WO4.2H2O, with phosphoric acid, H3PO4, acidified with hydrochloric acid, HCl.[2]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:[8]pH principal components1.0 [PW12O40]3a2.2 [PW12O40]3a, [P2W21O71]6a, [PW11O39]7a3.5 [PW12O40]3a, [P2W21O71]6a, [PW11O39]7a, [P2W18O62]6a, [P2W19O67]10a5.4 [P2W21O71]6a, [PW11O39]7a, [P2W18O62]6a7.3 [PW9O34]9a8.3 PO43a, WO42aThe species [PW11O39]7a is a lacunary, or defective Keggin ion. The [P2W18O62]6a has a Dawson structure. At pH less than 8, the presence of ethanol or acetone stabilises the anion, [PW12O40]3a, reducing decomposition.[8]Tungstophosphoric acid is thermally stable up to 400 AdegC, and is more stable than the analogous silicotungstic acid, H4SiW12O40.[9]Large quantities of polar molecules such as pyridine are absorbed into the bulk phase and not simply on the surface. Solid state NMR studies of ethanol absorbed in the bulk phase show that both protonated dimers, ((C2H5OH)2H+) and monomers, (C2H5OH2+) are present.Phosphotungstic acid is less sensitive to reduction than phosphomolybdic acid. Reduction with uric acid or iron(II) sulfate 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.[10]Phosphotungstic acid is the strongest of heteropolyacids. Its conjugate base is the PW12O403a anion.[11] 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.[12] One estimate of the acidity is that the solid has an acidity stronger than H0 =a13.16,[9] which would qualify the compound as a superacid. This acidic strength means that even at low pH the acid is fully dissociated.

89 AdegC

H3PW12O40

5 Per Day

1 Week

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100 Per Day

2 Days

Yes

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Africa, Middle East, Western Europe, Eastern Europe, South America, North America, Central America, Australia, Asia

Easy To Melt

Low

Bitter

Irregular

5.5 g/mL at 25 AdegC(lit.) Gram per millilitre (g/mL)

Granules

H2WO4

Yellow Free Flowing Powder

H3 PW12 O40

2880 Grams (g)

2000

Inorganic Acids

mundra

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3000000 Per Day

5 Days

Yes

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H2WO4

5.59 Gram per cubic meter (g/m3)

100 c

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05 Days

All India