Sodium trimetaphosphate

Sodium trimetaphosphate^[1]

Names
Other names Sodium trimetaphosphate
Identifiers
CAS Number	7785-84-4
3D model (Jmol)	Interactive image
ECHA InfoCard	100.029.171
EC Number	232-088-3
PubChem	24579
InChI InChI=1S/3Na.H3O9P3/c;;;1-10(2)7-11(3,4)9-12(5,6)8-10/h;;;(H,1,2)(H,3,4)(H,5,6)/q3*+1;/p-3
SMILES O=P(OP(O1)([O-])=O)([O-])OP1([O-])=O.[Na+].[Na+].[Na+]
Properties
Chemical formula	Na3P3O9
Molar mass	305.885 g/mol
Appearance	colorless or white crystals
Density	2.49 g/cm^3 (anhydrous) 1.786 g/cm^3 (hexahydrate)
Melting point	53 °C (127 °F; 326 K) (hexahydrate, decomposes to anyhdrous)
Solubility in water	22 g/100 mL
Solubility	insoluble in alcohol
Refractive index (nD)	1.433 (hexahydrate)
Structure
Crystal structure	triclinic (hexahydrate)
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

Sodium trimetaphosphate (also STMP), with formula Na₃P₃O₉, is a metaphosphate of sodium. It has the empirical formula NaPO₃. It is the sodium salt of trimetaphosphoric acid. It is a colourless solid that finds specialised applications in food and construction industries. STMP is prepared by heating sodium polyphosphate at a few hundred degrees. ^[2]

Although drawn with a particular resonance structure, the trianion has D_3d symmetry.

References

1. Lide, David R. (1998). Handbook of Chemistry and Physics (87 ed.). Boca Raton, FL: CRC Press. pp. 4–86. ISBN 0-8493-0594-2.
2. Klaus Schrödter, Gerhard Bettermann, Thomas Staffel, Friedrich Wahl, Thomas Klein, Thomas Hofmann "Phosphoric Acid and Phosphates" in Ullmann’s Encyclopedia of Industrial Chemistry 2008, Wiley-VCH, Weinheim. doi:10.1002/14356007.a19_465.pub3