Triphosphoric acid

Triphosphoric acid

Names
IUPAC name Diphosphono hydrogen phosphate
Identifiers
CAS Number	10380-08-2
ECHA InfoCard	100.030.752
UNII	NU43IAG5BC
InChI InChI=1S/H5O10P3/c1-11(2,3)9-13(7,8)10-12(4,5)6/h(H,7,8)(H2,1,2,3)(H2,4, 5,6)
Properties
Chemical formula	H5P3O10
Molar mass	257.95 g/mol
Acidity (pKa)	small, small, 2.30, 6.50, 9.24
Hazards
Main hazards	Corrosive (C)
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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Infobox references

Triphosphoric acid (also tripolyphosphoric acid), with formula H₅P₃O₁₀, is a condensed form of phosphoric acid. In the family of phosphoric acids, it is the next polyphosphoric acid after pyrophosphoric acid, H₄P₂O₇, 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 H₅P₃O₁₀ contains about 18% of triphosphoric acid. A solution of the pure species can be obtained by ion exchange of the sodium salt, sodium triphosphate, at 0 °C.^[1]

Various pK_a values are reported, 1.0 ; 2.2 ; 2.3 ; 5.7 ; 8.5,^[1] 1.0 ; 2.2 ; 2.3 ; 3.7 ; 8.5 ^[2]

References

1. Corbridge, D. (1995). "Chapter 3: Phosphates". Studies in inorganic Chemistry vol. 20. Elsevier Science B.V. pp. 169–305. ISBN 0-444-89307-5. Retrieved January 30, 2015. – via ScienceDirect (Subscription may be required or content may be available in libraries.)
2. Holleman, A. F.; Wiberg, E. (2001), Inorganic Chemistry, San Diego: Academic Press, p. 729, ISBN 0-12-352651-5