Sodium trimetaphosphate

Sodium trimetaphosphate[1]
Other names Sodium trimetaphosphate
Identifiers
CAS number	7785-84-4 Y
PubChem	24579
	EC number	232-088-3
Jmol-3D images	{{#if:O=P(OP(O1)([O-])=O)([O-])OP1([O-])=O.[Na+].[Na+].[Na+]|Image 1
SMILES O=P(OP(O1)([O-])=O)([O-])OP1([O-])=O.[Na+].[Na+].[Na+]
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
Properties
Molecular formula	Na3P3O9
Molar mass	305.885 g/mol
Appearance	colorless or white crystals
Density	2.49 g/cm3 (anhydrous) 1.786 g/cm3 (hexahydrate)
Melting point	53 °C (hexahydrate, decomp. to anyhdrous)
Solubility in water	22 g/100 mL
Solubility	insoluble in alcohol
Refractive index (nD)	1.433 (hexahydrate)
Structure
Crystal structure	triclinic (hexahydrate)
Y (verify) (what is: Y/N?) Except where noted otherwise, data are given for materials in their standard state (at 25 °C (77 °F), 100 kPa)
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