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Barium metaphosphate
Names
	IUPAC name barium(2+); dioxido(oxo)phosphanium
Identifiers
CAS Number	13762-83-9 ;
3D model (JSmol)	Interactive image;
ChemSpider	2341276;
ECHA InfoCard	100.033.951
EC Number	237-362-6;
PubChem CID	3084168;
CompTox Dashboard (EPA)	DTXSID30872575 ;
	InChI InChI=1S/Ba.2HO3P/c;21-4(2)3/h;2(H,1,2,3)/q+2;;/p-2 Key: XNJIKBGDNBEQME-UHFFFAOYSA-L;
	SMILES [O-][P+](=O)[O-].[O-][P+](=O)[O-].[Ba+2];
Properties
Chemical formula	Ba(PO3)2
Molar mass	295.27 g/mol
Appearance	Powder
Density	3.63 g/cm3
Melting point	1,560 °C (2,840 °F; 1,830 K)
	Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). Infobox references

Barium metaphosphate is an inorganic substance with the molecular formula Ba(PO₃)₂. It is a colourless solid that is insoluble in water, though is soluble in acidic solutions through "slow dissolution".^[3] X-ray crystallography shows that this material is composed of Ba²⁺ cations attached to a polyphosphate ((PO₃⁻)_n) anion.^[4] A number of hydrated forms are known which are actually cyclic metaphosphates, Ba₂(P₄O₁₂)·3.5H₂O, Ba₃(P₃O₉)₂·6H₂O.^{[citation needed]}

Structure of a subunit of linear polyphosphate anion.

Preparation

Barium metaphosphate can be prepared by the reaction of barium carbonate with metaphosphoric acid:^{[citation needed]}

BaCO₃ + 2HPO₃ → Ba(PO₃)₂ +CO₂ +H₂O

or alternatively by the aqueous reaction of barium chloride and sodium metaphosphate:^{[citation needed]} BaCl₂(aq) + 2NaPO₃(aq) → Ba(PO₃)₂ + 2NaCl

Applications

The combination of soda and barium polyphosphate forms a low-melting glass with a high coefficient of thermal expansion. The melting point of the glass increases with barium content. This glass makes seals with low melting metals like aluminium (melting point 650 °C). Normal borosilicate glasses soften above the melting point of aluminium. This mixture is prepared by heating a mixture of diammonium phosphate, sodium carbonate, and barium carbonate.^[5]

References

^ Elements, American. "Barium Metaphosphate". American Elements. Retrieved 17 April 2018.
^ "BARIUM METAPHOSPHATE - 13762-83-9". www.chemicalbook.com. Retrieved 17 April 2018.
^ "Barium Metaphosphate". Chemical Book. 2017. Retrieved November 27, 2017.
^ "Form of barium metaphosphate" Grenier, Jean C.; Martin, Claude M.; Durif, Andre; Tran Qui Duc; Guitel, J. C. Bulletin de la Société Francaise de Minéralogie et de Cristallographie (1967), vol. 90, 24-31.
^ Wilder Jr., J.A. "Glasses and glass ceramics for sealing to aluminum alloys" Journal of Non-Crystalline Solids Volume 38-39, Issue PART 2, May 1980, Pages 879-884. Hart, Patricia E.; Mesko, Melissa G.; Shelby, James E. "Crystallization and phase equilibrium in the sodium barium metaphosphate system" Journal of Non-Crystalline Solids (2000), 263&264, 305-311. doi:10.1016/S0022-3093(99)00642-0