Magnesum metaphosphate can be prepared by the
solid-state reaction of metaphosphoric acid and the
hydroxide, oxide or carbonate of magnesium:
MgCO3 + HPO3 + heat ? Mg(PO3)2 +H2O + CO2
The best temperature to use is about 700 C. It can
also be prepared by the aqueous reactions:
2NaPO3 (aq) + MgCl2 (aq) ? Mg(P3O9)2·xH2O (s)
+ 2NaCl
or
Mg(OH)2 (s) + 6 HPO3 (aq) ? Mg(P3O9)2·xH2O (s)
Calcium metaphosphate (CMP) has the molecular
formula of Ca(PO3)2 and the molecular weight of
198.0219 g/mol. Its CAS number is 13477-39-9.
This salt is also offered commercially as Calcium dimetaphosphate
(Ca(PO3)2) with the CAS number of
53801-86-8. Another manufacturer has a calcium bismetaphosphate
with the CAS number 53806-80-7. It is not
clear what differences may exist, if any, between these
salts or the method of their preparation. CMP can be
prepared by the solid-state reaction of metaphosphoric
acid and the hydroxide, oxide or carbonate of calcium:
CaCO3 + HPO3 + heat ? Ca(PO3)2 +H2O + CO2
