iron, metallic chemical element; symbol Fe [Lat. ferrum]; at. no. 26; at. wt. 55.845; m.p. about 1,535°C; b.p. about 2,750°C; sp. gr. 7.87 at 20°C; valence +2, +3, +4, or +6. Iron is biologically significant. Because iron is a component of hemoglobin, a red oxygen-carrying pigment of the red blood cells of vertebrates, iron compounds are important in nutrition; one cause of anemia is iron deficiency. For the history of the use of iron, see Iron Age.
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