Dissolve the salt in strong H2SO4 and slowly evaporate at ca 50o. Wash the crystals with glacial AcOH and then heat them in a furnace at a temperature of 450-500o for 6hours. Its solubility in H2O is 5%. The pentahydrate is converted to an anhydrous hygroscopic powder on heating at 500o for 6hours; but heating above this temperature over N2 yields the oxide-sulfate. Evaporation of neutral aqueous solutions provides basic sulfates. [Baxter & Alter J Am Chem Soc 55 1943 1933, Hattox & Vries J Am Chem Soc 58 2126 1936.]
