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.

[citation needed] Barium metaphosphate can be prepared by the reaction of barium carbonate with metaphosphoric acid:[citation needed] or alternatively by the aqueous reaction of barium chloride and sodium metaphosphate:[citation needed] BaCl2(aq) + 2NaPO3(aq) → Ba(PO3)2 + 2NaCl The combination of soda and barium polyphosphate forms a low-melting glass with a high coefficient of thermal expansion.

Normal borosilicate glasses soften above the melting point of aluminium.