Title: Iron
CAS Registry Number: 7439-89-6
Literature References: Fe; at. no. 26; at. wt 55.845; valences 2, 3; seldom 1, 4, 6. Group VIII (8). Four naturally occurring isotopes: 54 (5.82%); 56 (91.66%); 57 (2.19%); 58 (0.33%); artificial, radioactive isotopes: 52; 53; 55; 59-61. Second most abundant metal in earth's crust after aluminum: about 5%. The earth's core is believed to consist mainly of iron. Important ores include hematite (Fe2O3), magnetite (Fe3O4), limonite [FeO(OH).
nH2O] and
siderite (FeCO3). Essential dietary nutrient. Study of iron and its compds by M?ssbauer spectroscopy: Danon, "57Fe: Metal, Alloys and Inorganic Compounds" in
Chemical Applications of M?ssbauer Spectroscopy, V. I. Goldanskii, R. H. Herber, Eds. (Academic Press, New York, 1968) p 159-313. Ions involved in oxygen transport, electron transport, nitrogen fixation and a number of other biological processes: Nielands, "Evolution of Biological Iron Binding Centers" in
Struct. Bonding 11, 145-170 (1972). Review of biology, pharmacology and toxicity of iron compounds: several authors,
Clin. Toxicol. 4, 525-642 (1971); of metabolism and homeostasis: G. Papanikolaou, K. Pantopoulos,
Toxicol. Appl. Pharmacol. 202, 199-211 (2005). Comprehensive reviews: Feldmann, Schenck in
Ullmanns Encyklop?die der technischen Chemie vol. 6 (München-Berlin, 1955) pp 261-407; Nicholls in
Comprehensive Inorganic Chemistry vol. 3, J. C. Bailar, Jr.
et al., Eds. (Pergamon Press, Oxford, 1973) pp 979-1051; W. A. Knepper in
Kirk-Othmer Encyclopedia of Chemical Technology vol. 13 (Wiley-Interscience, New York, 3rd ed., 1981) pp 735-753. Review of use in cereal flour fortification: R. Hurrell
et al., Nutr. Rev. 60, 391-406 (2002).
Properties: Silvery-white or gray, soft, ductile, malleable, somewhat magnetic metal. Holds magnetism only after hardening (as alloy steel,
e.g., Alnico). Supplied as ingots, powder, wire, sheets, etc. Takes a bright polish; can be rolled, hammered, bent, particularly when red hot. Stable in dry air but readily oxidizes in moist air, forming "rust" (chiefly oxide, hydrated). In powder form it is black to gray. Commercial iron usually contains some C, P, Si, S and Mn. d pure 7.86; cast 7.76; wrought 7.25-7.78; steel 7.6-7.78. mp pure 1535°; cast 1000-1300°; wrought 1500°; steel 1300°. bp 3000°. Electrical resistivity (20°): 9.71 microhm-cm. Readily attacked by dil mineral acids and attacked or dissolved by organic acids; not appreciably attacked by cold concd H2SO4 or HNO3, but is attacked by the hot acids.
Melting point: mp pure 1535°; cast 1000-1300°; wrought 1500°; steel 1300°
Boiling point: bp 3000°
Density: d pure 7.86; cast 7.76; wrought 7.25-7.78; steel 7.6-7.78
Use: Alloyed with C, Mn, Cr, Ni, and other elements to form steels. Nutritional supplement in wheat flours, corn meal, grits and other cereal products. 55Fe and 59Fe used in tracer studies; the former in biological studies.
