描述
Iron oxide, also known as eisen(ii)-oxid or ferrous oxide, is a member of the class of compounds known as transition metal oxides. Transition metal oxides are inorganic compounds containing an oxygen atom of an oxidation state of -2, in which the heaviest atom bonded to the oxygen is a transition metal. Iron oxide can be found in cocoa bean and common hazelnut, which makes iron oxide a potential biomarker for the consumption of these food products. Iron oxides and oxide-hydroxides are wide spread in nature, play an important role in many geological and biological processes, and are widely used by humans, e.g., as iron ores, pigments, catalysts, in thermite (see the diagram) and hemoglobin. Common rust is a form of iron(III) oxide. Iron oxides are widely used as inexpensive, durable pigments in paints, coatings and colored concretes. Colors commonly available are in the "earthy" end of the yellow/orange/red/brown/black range. When used as a food coloring, it has E number E172 .