... : 23% Fe3O4(%): 96, r esldue: 0.3%, soluble in water IRON OXIDE BLACKFormula:Fe3O4Molecure weight:231.54Chemical-Physcial PropertoesAppearance: S/G ... to heat under 100. Oxidized to red iron oxide at high tmperature. Become gama-iron oxide when ignition at 200-300 .Usage ... used in concrete coloring, paintings, printing inks, coating & brick making. Iron oxide black for paint