Synthesis of poorly crystalline iron(III) hydrous oxides and basic salts (ferrihydrite, schwertmannite, and jarosite) consisting of uniform spherical particles of characteristic shape with a diameter of similar to 10 mu m is described. The preparation procedure is based on homogeneous precipitation of aqueous solutions of Fe-2(SO4)(3) with urea in the temperature range 60-100 degrees C. Thermal dehydration of iron(III) hydroxide leads to an amorphous ferric oxide with a high surface area (similar to 200 m(2)/g) that is stable up to about 500 degrees C.