Iron arsenate powder

Patent Granted There is provided an iron arsenate powder which is produced from an arsenic containing solution and wherein the concentration of arsenic eluted or released from the powder is very low. The iron arsenate powder is a powder of dihydrate of iron arsenate, which has a crystal structure of rhombic system and which has lattice constants of a = 0.8950 to 0.8956 nm, b = 1.0321 to 1.0326 nm and c = 1.0042 to 1.0050 nm at room temperatures and atmospheric pressure.