Barium metaphosphate
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 Ba cations attached to a polyphosphate ((PO3)n) anion. A number of hydrated forms are known which are actually cyclic metaphosphates, Ba2(P4O12)·3.5H2O, Ba3(P3O9)2·6H2O.