Promethium(III) phosphate is an inorganic compound, a salt of promethium and phosphate, with the chemical formula of PmPO<sub>4</sub>. It is radioactive. Its hydrate can be obtained by precipitation of soluble promethium salt and diammonium hydrogen phosphate at pH 3~4 (or obtained by hydrothermal reaction ), and the hydrate can be obtained by burning at 960 ðC to obtain the anhydrous form. Its standard enthalpy of formation is âÂÂ464 kcal/mol.