Triphosphoric acid (also tripolyphosphoric acid), with formula H
5P
3O
10, is a
condensed form of
phosphoric acid. In the family of
phosphoric acids, it is the next polyphosphoric acid after
pyrophosphoric acid, H
4P
2O
7, also called diphosphoric acid.
Compounds such as ATP (
adenosine triphosphate) are
esters of triphosphoric acid.
Triphosphoric acid has not been obtained in crystalline form. The equilibrium mixture with an overall composition corresponding to H
5P
3O
10 contains about 20% of triphosphoric acid. A solution of the pure species can be obtained by ion exchange of the sodium salt,
sodium triphosphate, at 0 °C.
Triphosporic acid is a
pentaprotic acid, meaning that it can release five protons in basic enough conditions. Sources differ on the corresponding p''K''
a values:
* 1.0; 2.2; 2.3; 5.7; 8.5
* 1.0; 2.2; 2.3; 3.7; 8.5
* small; small; 2.30; 6.50; 9.24
References
Phosphorus oxoacids
Phosphorus(V) compounds
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