Pyrophosphoric acid #CAS2466-09-3
CAS Number:2466-09-3
Chemical Formula:CoH2O2
Synonyms:
Pyrophosphoric acid technical grade
Pyrophosphoric acidDiphosphoric acid
Diphosphoric(V) acid
Appearance:Anhydrous form: Colorless acicular crystals or white waxy solid, with two crystal forms (Form I mp 54.3°C, Form II mp 71.5°C); Aqueous solution: Colorless to pale yellow transparent viscous liquid. Extremely hygroscopic, crystallizes on standing, slowly hydrolyzes to orthophosphoric acid in water, strong acidity and corrosivity
MOQ (Minimum Order Quantity): 1 FCL (Full Container Load)
Pyrophosphoric acid #CAS2466-09-3
Pyrophosphoric acid, also known under the name diphosphoric acid, is colorless, odorless, hygroscopic and is soluble in water, diethyl ether and ethyl alcohol. It is produced from phosphoric acid by dehydration. Pyrophosphoric acid slowly hydrolyzes in the presence of water into phosphoric acid.
H4P2O7 +H2O2H3PO4
Upon heating, phosphoric acid loses water, being converted successively, and to some extent concurrently, into the pyro- and meta-acids:
2H3PO4H4P2O7 +H2O
nH3PO4(HPO3)n + [H2O]n
The acid has four replacable H+ ions. Its dissociation constants indicate that two H+ ions are strongly acidic while the other two protons are weakly acidic. The first dissociation constant especially is very large:
H4P2O7 + H2O ↔ H3O+ + H3P2O7¯ Ka1 ~ 10–1
H3P2O7¯+ H2O ↔ H3O+ + H2P2O72– Ka2 ~ 1.5x10–2
PHOSPHORIC ACID, PYRO 701H2P2O72¯ + H2O ↔ H3O+ + HP2O73– Ka3 ~ 2.7x10–7
HP2O73¯ + H2O ↔ H3O+ + P2O74¯ Ka4 ~ 2.4x10–10
Pyrophosphoric acid forms acid salts, such as NaH3P2O7 and Na2H2P2O7.
Pyrophosphoric acid may be prepared by heating orthophosphoric acid at 215°C:
2H3PO4 → H4P2O7 + H2O
The acid solution in pure form can be obtained by ion exchange, passing an aqueous solution of sodium pyrophosphate, Na4P2O7, through a suitable cation exchange column.According to early investigators, the pyro-acid is formed as low as 100 °C, and the conversion is complete between 255 and 260 °C. Phosphorous oxychloride reacts with phosphoric acid in the following manner:
5H3PO4 + POC133H4P2O7 + 3HC1
A mixture of the ortho- and meta-acids may be condensed together to form the pyro-acid by heating on the water bath:
nH3PO4 +[HPO3]n[H4P2O7]n
Application of Pyrophosphoric acid
Pyrophosphoric Acid has been shown to enhance the rate of pyrophosphate hydrolysis by nonenzymatic catlysis and by inorganic pyrophoshatase. Pyrophosphoric Acid can be used for the preparation of vanadyl pyrophosphato methoxide cluster anion. Pyrophosphoric Acid is used in anion binding of inorganic phosphates due to is ability to form complexes.
Catalyst, manufacture of organic phosphate esters, metal treatment, stabilizer for organic per- oxides.
| Pyrophosphoric acid Chemical Properties |
| Melting point | 61 °C |
| density | approximate 1.9g/ml (25℃) |
| storage temp. | -20°C, Hygroscopic |
| solubility | DMSO (Soluble) |
| pka | 0.99±0.10(Predicted) |
| form | white crystals |
| color | white crystals, crystalline |
| PH | pKa1= 0.86, pKa2 = 1.76, pKa3 = 5.88, pKa4 = 8.14(25℃) |
| Water Solubility | 709g/100mL H2O (23°C); soluble alcohol, ether [MER06] |
| Merck | 13,8098 |
| Stability: | Hygroscopic, Moisture Sensitive |
| InChI | InChI=1S/H4O7P2/c1-8(2,3)7-9(4,5)6/h(H2,1,2,3)(H2,4,5,6) |
| InChIKey | XPPKVPWEQAFLFU-UHFFFAOYSA-N |
| SMILES | P(OP(O)(=O)O)(O)(O)=O |
| CAS DataBase Reference | 2466-09-3(CAS DataBase Reference) |
| EPA Substance Registry System | Diphosphoric acid (2466-09-3) |
| Safety Information |
| Hazard Codes | C |
| Risk Statements | 22-34 |
| Safety Statements | 26-36/37/39-45 |
| RIDADR | UN 3260 8/PG 2 |
| WGK Germany | 3 |
| RTECS | JL6672500 |
| F | 3-9-21 |
| HazardClass | 8 |
| PackingGroup | III |
| HS Code | 28092000 |
| Storage Class | 8B - Non-combustible corrosive hazardous materials |
| Hazard Classifications | Acute Tox. 4 Oral Skin Corr. 1B |
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