Barium metaphosphate

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Barium metaphosphate
IUPAC name
barium(2+); dioxido(oxo)phosphanium
ECHA InfoCard 100.033.951
Molar mass 295.27 g/mol
Appearance Powder[1]
Density 3.63 g/cm3
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. X-ray crystallography shows that this material is composed of Ba2+ cations attached to a polyphosphate ((PO3)n) anion.[2] A number of hydrated forms are known which are actually cyclic metaphosphates, Ba2(P4O12)·3.5H2O, Ba3(P3O9)2·6H2O.[3]

Structure of a subunit of linear polyphosphate anion.


Barium metaphosphate can be prepared by the reaction of barium carbonate with metaphosphoric acid:[3]-

BaCO3 + 2HPO3 → Ba(PO3)2 +CO2 +H2O

or alternatively by the aqueous reaction of barium chloride and sodium metaphosphate:[3]- BaCl2(aq) + 2NaPO3(aq) → Ba(PO3)2 + 2NaCl


The combination of sodium 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.[4]


  1. ^
  2. ^ "Form of barium metaphosphate" Grenier, Jean C.; Martin, Claude M.; Durif, Andre; Tran Qui Duc; Guitel, J. C. Bulletin de la Societe Francaise de Mineralogie et de Cristallographie (1967), vol. 90, 24-31.
  3. ^ a b c Ropp, Richard (2012). Encyclopedia of the Alkaline Earth Compounds. Newnes. p. 76. ISBN 0444595538. 
  4. ^ 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