sodium iodide; HCl in water reducing 0.1-0.5 M NaMnO4*H2O with 0.1-0.5 M NaI at pH <5-8 (NaI/NaMnO4 ratio = 0.2-5), stirring for 24 h, filtration, washing with water, drying in air, firing in air for 24 h at 600°C; X-ray diffraction anal.;