Actinium(III) phosphate is a white-colored chemical compound of the radioactive element actinium. This compound was created by reacting actinium(III) chloride with monosodium phosphate in aqueous hydrochloric acid. This resulted in the hemihydrate AcPO4·1/2H2O, whose structure was confirmed by x-ray diffraction to match that of lanthanum phosphate. To become anhydrous, it was heated to 700 °C, which resulted in a solid that was black (presumably due to the presence of impurities), and whose specific X-ray structure did not match that of other known correspond to other actinide phosphates.[1]