Iron: Wikis


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lustrous metallic with a grayish tinge
A rough wedge of silvery metal
General properties
Name, symbol, number iron, Fe, 26
Element category transition metal
Group, period, block 84, d
Standard atomic weight 55.845(2)g·mol−1
Electron configuration [Ar] 3d6 4s2
Electrons per shell 2, 8, 14, 2 (Image)
Physical properties
Phase solid
Density (near r.t.) 7.874 g·cm−3
Liquid density at m.p. 6.98 g·cm−3
Melting point 1811 K, 1538 °C, 2800 °F
Boiling point 3134 K, 2862 °C, 5182 °F
Heat of fusion 13.81 kJ·mol−1
Heat of vaporization 340 kJ·mol−1
Specific heat capacity (25 °C) 25.10 J·mol−1·K−1
Vapor pressure
P/Pa 1 10 100 1 k 10 k 100 k
at T/K 1728 1890 2091 2346 2679 3132
Atomic properties
Electronegativity 1.83 (Pauling scale)
Ionization energies
1st: 762.5 kJ·mol−1
2nd: 1561.9 kJ·mol−1
3rd: 2957 kJ·mol−1
Atomic radius 126 pm
Covalent radius 132±3 (low spin), 152±6 (high spin) pm
Crystal structure body-centered cubic
Magnetic ordering ferromagnetic
1043 K
Electrical resistivity (20 °C) 96.1 nΩ·m
Thermal conductivity (300 K) 80.4 W·m−1·K−1
Thermal expansion (25 °C) 11.8 µm·m−1·K−1
Speed of sound (thin rod) (r.t.) (electrolytic)
5120 m·s−1
Young's modulus 211 GPa
Shear modulus 82 GPa
Bulk modulus 170 GPa
Poisson ratio 0.29
Mohs hardness 4
Vickers hardness 608 MPa
Brinell hardness 490 MPa
CAS registry number 7439-89-6
Most stable isotopes
Main article: Isotopes of iron
iso NA half-life DM DE (MeV) DP
54Fe 5.8% >3.1×1022y 2ε capture  ? 54Cr
55Fe syn 2.73 y ε capture 0.231 55Mn
56Fe 91.72% 56Fe is stable with 30 neutrons
57Fe 2.2% 57Fe is stable with 31 neutrons
58Fe 0.28% 58Fe is stable with 32 neutrons
59Fe syn 44.503 d β 1.565 59Co
60Fe syn 2.6×106 y β 3.978 60Co

Iron (pronounced /ˈаɪ.ərn/) is a metallic chemical element with the symbol Fe (Latin: ferrum) and atomic number 26. Iron is a group 8 and period 4 element and is therefore classified as a transition metal. Iron and iron alloys (steels) are by far the most common metals and the most common ferromagnetic materials in everyday use. Fresh iron surfaces are lustrous and silvery-grey in color, but oxidize in air to form a red or brown coating of ferric oxide or rust. Pure single crystals of iron are soft (softer than aluminium), and the addition of minute amounts of impurities, such as carbon, significantly strengthens them. Alloying iron with appropriate small amounts (up to a few per cent) of other metals and carbon produces steel, which can be 1,000 times harder than pure iron.

Iron-56 is the heaviest stable isotope produced by the alpha process in stellar nucleosynthesis; heavier elements than iron and nickel require a supernova for their formation. Iron is the most abundant element in the core of red giants, and is the most abundant metal in iron meteorites and in the dense metal cores of planets such as Earth.



Pure iron is a metal but is rarely found in this form on the surface of the earth because it oxidizes readily in the presence of oxygen and moisture. In order to obtain metallic iron, oxygen must be removed from naturally occurring ores by chemical reduction – mainly of the iron ore hematite (Fe2O3) by carbon at high temperature. The properties of iron can be modified by alloying it with various other metals (and some non-metals, notably carbon and silicon) to form steels.

Nuclei of iron atoms have some of the highest binding energies per nucleon, surpassed only by the nickel isotope 62Ni. The universally most abundant of the highly stable nuclides is, however, 56Fe. This is formed by nuclear fusion in stars. Although a further tiny energy gain could be extracted by synthesizing 62Ni, conditions in stars are unsuitable for this process to be favoured. Elemental distribution on Earth greatly favours iron over nickel, and also presumably in supernova element production.[1]

Iron (as Fe2+, ferrous ion) is a necessary trace element used by almost all living organisms. The only exceptions are several organisms that live in iron-poor environments and have evolved to use different elements in their metabolic processes, such as manganese instead of iron for catalysis, or hemocyanin instead of hemoglobin. Iron-containing enzymes, usually containing heme prosthetic groups, participate in catalysis of oxidation reactions in biology, and in transport of a number of soluble gases. See hemoglobin, cytochrome, and catalase.

Mechanical properties

Characteristic values of tensile strength (TS) and Brinell hardness (BH) of different forms of iron.[2][3]
Material TS (MPa) BH (Brinell)
Iron whiskers 11000
Ausformed (hardened) steel 2930 850–1200
Martensitic steel 2070 600
Bainitic steel 1380 400
Pearlitic steel 1200 350
Cold-worked iron 690 200
Small-grain iron 340 100
Iron containing dissolved carbon 140 40
Single crystal of pure iron 10 3

Mechanical properties of iron and its alloys are evaluated using a variety of tests, such as the Brinell test, Rockwell test, or tensile strength tests, among others; the results are so consistent that tests of iron are often used to relate the results of one test to another.[3][4] Those measurements reveal that mechanical properties of iron crucially depend on purity: Purest research-purpose single crystals of iron are softer than aluminium. Addition of only 10 parts per million of carbon doubles their strength.[2] The hardness increases rapidly with carbon content up to 0.2% and saturates at ~0.6%.[5] The purest industrially produced iron (about 99.99% purity) has a hardness of 20–30 Brinell.[6]


Iron represents perhaps the best-known example of allotropy in a metal. There are three allotropic forms of iron, known as α, γ and δ.

As molten iron cools down it crystallizes at 1538 °C into its δ allotrope, which has a body-centred cubic (bcc) crystal structure. As it cools further its crystal structure changes to face-centred cubic (fcc) at 1394 °C, when it is known as γ-iron, or austenite. At 912 °C the crystal structure again becomes bcc as α-iron, or ferrite, is formed, and at 770 °C (the Curie point, Tc) the iron becomes magnetic. As the iron passes through the Curie temperature there is no change in crystalline structure, but there is a change in "domain structure", where each domain contains iron atoms with a particular electronic spin. In unmagnetized iron, all the electronic spins of the atoms within one domain are in the same direction; however, in neighbouring domains they point in various directions and thus cancel out. In magnetized iron, the electronic spins of all the domains are all aligned, so that the magnetic effects of neighbouring domains reinforce each other. Although each domain contains billions of atoms, they are very small, about 10 microns across.

Iron is of greatest importance when mixed with certain other metals and with carbon to form steels. There are many types of steels, all with different properties; and an understanding of the properties of the allotropes of iron is key to the manufacture of good quality steels.

Alpha iron, also known as ferrite, is the most stable form of iron at normal temperatures. It is a fairly soft metal that can dissolve only a small concentration of carbon (no more than 0.021% by mass at 910 °C).[7]

Above 912 °C and up to 1400 °C α-iron undergoes a phase transition from body-centred cubic to the face-centred cubic configuration of γ-iron, also called austenite. This is similarly soft and metallic but can dissolve considerably more carbon (as much as 2.04% by mass at 1146 °C). This form of iron is used in the type of stainless steel used for making cutlery, and hospital and food-service equipment.


River water flows over some rocks, turning a bright, cloudy reddish-orange as it does so.
The red appearance of this water is due to ferric ions, iron(III) or Fe3+, in the rocks.

Iron is the sixth most abundant element in the Universe, formed as the final act of nucleosynthesis, by silicon fusing in massive stars. While it makes up about 5% of the Earth's crust, the Earth's core is believed to consist largely of an iron-nickel alloy constituting 35% of the mass of the Earth as a whole. Iron is consequently the most abundant element on Earth, but only the fourth most abundant element in the Earth's crust.[8] Most of the iron in the crust is found combined with oxygen as iron oxide minerals such as hematite and magnetite.

About 1 in 20 meteorites consist of the unique iron-nickel minerals taenite (35–80% iron) and kamacite (90–95% iron). Although rare, iron meteorites are the major form of natural metallic iron on the Earth's surface.

The red color of the surface of Mars is thought to derive from an iron oxide-rich regolith.


Naturally occurring iron consists of four stable isotopes: 5.845% of 54Fe, 91.754% of 56Fe, 2.119% of 57Fe and 0.282% of 58Fe. The nuclide 54Fe is predicted to undergo double beta decay, but this process had never been observed experimentally for these nuclei, and only the lower limit on the half-life was established: T1/2>3.1×1022 years. 60Fe is an extinct radionuclide of long half-life (2.6 million years).

Much of the past work on measuring the isotopic composition of Fe has centred on determining 60Fe variations due to processes accompanying nucleosynthesis (i.e., meteorite studies) and ore formation. In the last decade however, advances in mass spectrometry technology have allowed the detection and quantification of minute, naturally occurring variations in the ratios of the stable isotopes of iron. Much of this work has been driven by the Earth and planetary science communities, although applications to biological and industrial systems are beginning to emerge.[9]

The most abundant iron isotope 56Fe is of particular interest to nuclear scientists. A common misconception is that this isotope represents the most stable nucleus possible, and that it thus would be impossible to perform fission or fusion on 56Fe and still liberate energy. This is not true, as both 62Ni and 58Fe are more stable, being the most stable nuclei. However, since 56Ni is much more easily produced from lighter nuclei in the alpha process in nuclear reactions in supernovae (see silicon burning process), nickel-56 (14 alpha particles) is the endpoint of fusion chains inside extremely massive stars, since addition of another alpha would result in zinc-60, which requires a great deal more energy. This nickel-56, which has a half-life of about 6 days, is therefore made in quantity in these stars, but soon decays by two successive positron emissions within supernova decay products in the supernova remnant gas cloud, to first radioactive cobalt-56, and then stable iron-56. This last nuclide is therefore common in the universe, relative to other stable metals of approximately the same atomic weight.

In phases of the meteorites Semarkona and Chervony Kut a correlation between the concentration of 60Ni, the daughter product of 60Fe, and the abundance of the stable iron isotopes could be found which is evidence for the existence of 60Fe at the time of formation of the solar system. Possibly the energy released by the decay of 60Fe contributed, together with the energy released by decay of the radionuclide 26Al, to the remelting and differentiation of asteroids after their formation 4.6 billion years ago. The abundance of 60Ni present in extraterrestrial material may also provide further insight into the origin of the solar system and its early history. Of the stable isotopes, only 57Fe has a nuclear spin (−1/2).

Chemistry and compounds

Iron forms compounds mainly in the +2 and +3 oxidation states. Traditionally, iron(II) compounds have been called ferrous, and iron(III) compounds ferric. There are many compounds in each of the oxidation states; representative examples would include iron(II) sulfate (FeSO4) and iron(III) chloride (FeCl3). There are also numerous examples of compounds that contain iron atoms in both of these oxidation states, such as magnetite and prussian blue. The ferrate anion [FeO4]2− contains an iron(VI) centre, its highest known oxidation state, and is present, for example in potassium ferrate (K2FeO4). There are numerous organometallic compounds (such as iron pentacarbonyl) that contain formally zerovalent (or lower) iron.

Iron is susceptible to oxidation in the presence of air and water, and reacts slowly to form ferric oxide (rust). As a result, iron that is intended for applications where exposure to water is likely must be protected, either through the use of sacrificial metals like magnesium or through galvanisation with zinc.


A circle, with a short, simple arrow shape extending diagonally upwards and rightwards from its edge
The symbol for Mars has been used since ancient times to represent iron.
An pillar, slightly fluted, with some ornamentation at its top. It is black, slightly weathered to a dark brown near the base. It is around 7 meters (22 feet) tall. It stands upon a raised circular base of stone, and is surrounded by a short, square fence.
The Delhi iron pillar is an example of the iron extraction and processing methodologies of India. The iron pillar at Delhi has withstood corrosion for the last 1600 years.

The first wrought iron used by mankind during prehistory came from meteorites. The smelting of iron in bloomeries began in the second millennium BC. Artifacts from smelted iron occur in India from 1800–1200 BC,[10] and in the Levant from about 1500 BC (suggesting smelting in Anatolia or the Caucasus).[11][12]

Cast iron was first produced in China about 550 BC,[13] but not in Europe until the medieval period[citation needed]. During the medieval period, means were found in Europe of producing wrought iron from cast iron (in this context known as pig iron) using finery forges. For all these processes, charcoal was required as fuel.

Steel (with smaller carbon content than pig iron but more than wrought iron) was first produced in antiquity. New methods of producing it by carburizing bars of iron in the cementation process were devised in the 17th century AD. In the Industrial Revolution, new methods of producing bar iron without charcoal were devised and these were later applied to produce steel. In the late 1850s, Henry Bessemer invented a new steelmaking process, involving blowing air through molten pig iron, to produce mild steel. This and other 19th century and later processes have led to wrought iron no longer being produced.

Industrial production

Several matte-black irregular pellets
Iron ore pellets from Kiruna, Sweden.

The production of iron or steel is a process unless the desired final product is cast iron. The first stage is to produce pig iron in a blast furnace. The second is to make wrought iron or steel from pig iron by a further process.

Blast furnace

Ninety percent of all mining of metallic ores is for the extraction of iron. Industrially, iron is produced starting from iron ores, principally hematite (nominally Fe2O3) and magnetite (Fe3O4) by a carbothermic reaction (reduction with carbon) in a blast furnace at temperatures of about 2000 °C. In a blast furnace, iron ore, carbon in the form of coke, and a flux such as limestone (which is used to remove impurities in the ore which would otherwise clog the furnace with solid material) are fed into the top of the furnace, while a blast of heated air is forced into the furnace at the bottom.

Iron output in 2005

In the furnace, the coke reacts with oxygen in the air blast to produce carbon monoxide:

2 C + O2 → 2 CO

The carbon monoxide reduces the iron ore (in the chemical equation below, hematite) to molten iron, becoming carbon dioxide in the process:

3 CO + Fe2O3 → 2 Fe + 3 CO2

The flux is present to melt impurities in the ore, principally silicon dioxide sand and other silicates. Common fluxes include limestone (principally calcium carbonate) and dolomite (calcium-magnesium carbonate). Other fluxes may be used depending on the impurities that need to be removed from the ore. In the heat of the furnace the limestone flux decomposes to calcium oxide (quicklime):

CaCO3 → CaO + CO2

Then calcium oxide combines with silicon dioxide to form a slag.

CaO + SiO2 → CaSiO3

The slag melts in the heat of the furnace. In the bottom of the furnace, the molten slag floats on top of the denser molten iron, and apertures in the side of the furnace are opened to run off the iron and the slag separately. The iron once cooled, is called pig iron, while the slag can be used as a material in road construction or to improve mineral-poor soils for agriculture.[citation needed]

How iron was extracted in the 19th century
This heap of iron ore pellets will be used in steel production.

In 2005, approximately 1,544 million metric tons of iron ore were produced worldwide. According to the British Geological Survey, China was the top producer of iron ore with at least one quarter world share, followed by Brazil, Australia and India.

Further processes

Pig iron is not pure iron, but has 4–5% carbon dissolved in it with small amounts of other impurities like sulfur, magnesium, phosphorus and manganese. As the carbon is the major impurity, the iron (pig iron) becomes brittle and hard. This form of iron is used to cast articles in foundries such as stoves, pipes, radiators, lamp-posts and rails.

Alternatively pig iron may be made into steel (with up to about 2% carbon) or wrought iron (commercially pure iron). Various processes have been used for this, including finery forges, puddling furnaces, Bessemer converters, open hearth furnaces, basic oxygen furnaces, and electric arc furnaces. In all cases, the objective is to oxidize some or all of the carbon, together with other impurities. On the other hand, other metals may be added to make alloy steels.

The hardness of the steel depends upon its carbon content, the higher the proportion of carbon, the greater the hardness and the lesser the ductility. The properties of the steel can also be changed by tempering it. To harden the steel, it is heated to red hot and then cooled by quenching it in the water. It becomes harder and more brittle. This steel is then heated to a required temperature and allowed to cool. The steel thus formed is less brittle.


Elemental iron

Iron is the most widely used of all the metals, accounting for 95% of worldwide metal production. Its low cost and high strength make it indispensable in engineering applications such as the construction of machinery and machine tools, automobiles, the hulls of large ships, and structural components for buildings. Since pure iron is quite soft, it is most commonly used in the form of steel. Commercially available iron is classified based on purity and the abundance of additives. Pig iron has 3.5–4.5% carbon[14] and contains varying amounts of contaminants such as sulfur, silicon and phosphorus. Pig iron is not a saleable product, but rather an intermediate step in the production of cast iron and steel from iron ore. Cast iron contains 2–4% carbon, 1–6% silicon, and small amounts of manganese. Contaminants present in pig iron that negatively affect material properties, such as sulfur and phosphorus, have been reduced to an acceptable level. It has a melting point in the range of 1420–1470 K, which is lower than either of its two main components, and makes it the first product to be melted when carbon and iron are heated together. Its mechanical properties vary greatly, dependent upon the form carbon takes in the alloy. "White" cast irons contain their carbon in the form of cementite, or iron carbide. This hard, brittle compound dominates the mechanical properties of white cast irons, rendering them hard, but unresistant to shock. The broken surface of a white cast iron is full of fine facets of the broken carbide, a very pale, silvery, shiny material, hence the appellation. In grey iron the carbon exists free as fine flakes of graphite, and also renders the material brittle due to the stress-raising nature of the sharp edged flakes of graphite. A newer variant of grey iron, referred to as ductile iron is specially treated with trace amounts of magnesium to alter the shape of graphite to spheroids, or nodules, vastly increasing the toughness and strength of the material.

The fining process of smelting iron ore to make wrought iron from pig iron, with the right illustration displaying men working a blast furnace, from the Tiangong Kaiwu encyclopedia, published in 1637 by Song Yingxing.

Wrought iron contains less than 0.25% carbon.[14] It is a tough, malleable product, but not as fusible as pig iron. If honed to an edge, it loses it quickly. Wrought iron is characterized by the presence of fine fibres of slag entrapped in the metal. Wrought iron is more corrosion resistant than steel. It has been almost completely replaced by mild steel for traditional "wrought iron" products and blacksmithing. Mild steel corrodes more readily that wrought iron, but is cheaper and more widely available. Carbon steel contains 2.0% carbon or less,[15] with small amounts of manganese, sulfur, phosphorus, and silicon. Alloy steels contain varying amounts of carbon as well as other metals, such as chromium, vanadium, molybdenum, nickel, tungsten, etc. Their alloy content raises their cost, and so they are usually only employed for specialist uses. Recent developments in ferrous metallurgy have produced a growing range of microalloyed steels, also termed 'HSLA' or high-strength, low alloy steels, containing tiny additions to produce high strengths and often spectacular toughness at minimal cost.

The main disadvantage of iron and steel is that pure iron, and most of its alloys, suffer badly from rust if not protected in some way. Painting, galvanization, passivation, plastic coating and bluing are all used to protect iron from rust by excluding water and oxygen or by sacrificial protection.

Iron compounds

Some canary-yellow powder sits, mostly in lumps, on a laboratory watch glass.
Iron chloride hexahydrate

Iron-based coordination complexes are being increasingly studied for Fisher-Tropsch and transfer-hydrogenation catalysis due to relatively high abundance and low cost of the metal. Specifically, iron analogues of existing ruthenium and osmium-based catalysts are being tested for activity because iron is isoelectronic with the more expensive second- and third-row transition metals and therefore exhibits similar reactivity.[20] The use of iron compounds in organic synthesis is mainly for the reduction of nitro compounds.[21] Additionally, iron has been used for desulfurizations,[22] reduction of aldehydes,[23] and the deoxygenation of amine oxides.[24]

Biological role

Structure of Heme b

Iron is essential to nearly all known organisms. In cells, iron is generally stored in the centre of metalloproteins, because "free" iron (which binds non-specifically to many cellular components) can catalyse production of toxic free radicals. Iron deficiency can lead to iron deficiency anemia.

In animals, plants, and fungi, iron is often the metal ion incorporated into the heme complex. Heme is an essential component of cytochrome proteins, which mediate redox reactions, and of oxygen carrier proteins such as hemoglobin, myoglobin, and leghemoglobin. Inorganic iron also contributes to redox reactions in the iron-sulfur clusters of many enzymes, such as nitrogenase (involved in the synthesis of ammonia from nitrogen and hydrogen) and hydrogenase. Non-heme iron proteins include the enzymes methane monooxygenase (oxidizes methane to methanol), ribonucleotide reductase (reduces ribose to deoxyribose; DNA biosynthesis), hemerythrins (oxygen transport and fixation in marine invertebrates) and purple acid phosphatase (hydrolysis of phosphate esters).

Iron distribution is heavily regulated in mammals, partly because iron has a high potential for biological toxicity[25]. Iron distribution is also regulated because many bacteria require iron, so restricting its availability to bacteria (generally by sequestering it inside cells) can help to prevent or limit infections. This is probably the reason for the relatively low amounts of iron in mammalian milk. A major component of this regulation is the protein transferrin, which binds iron absorbed from the duodenum and carries it in the blood to cells.[26]

Dietary sources

Good sources of dietary iron include red meat, fish, poultry, lentils, beans, leaf vegetables, tofu, chickpeas, black-eyed peas, fortified bread, and fortified breakfast cereals. Iron in low amounts is found in molasses, teff and farina. Iron in meat (haem iron) is more easily absorbed than iron in vegetables,[27] but heme/hemoglobin from red meat has effects which may increase the likelihood of colorectal cancer.[28][29]

Iron provided by dietary supplements is often found as iron (II) fumarate, although iron sulfate is cheaper and is absorbed equally well. Elemental iron, despite being absorbed to a much smaller extent (stomach acid is sufficient to convert some of it to ferrous iron), is often added to foods such as breakfast cereals or "enriched" wheat flour (where it is listed as "reduced iron" in the list of ingredients). Iron is most available to the body when chelated to amino acids - iron in this form is ten to fifteen times more bioavailable[30] than any other, and is also available for use as a common iron supplement. Often the amino acid chosen for this purpose is the cheapest and most common amino acid, glycine, leading to "iron glycinate" supplements.[31] The RDA for iron varies considerably based on age, gender, and source of dietary iron (heme-based iron has higher bioavailability).[32] Infants may require iron supplements if they are bottle-fed cow's milk.[33] Blood donors and pregnant women are at special risk of low iron levels and are often advised to supplement their iron intake.[citation needed]

Regulation of uptake

Iron uptake is tightly regulated by the human body, which has no regulated physiological means of excreting iron. Only small amounts of iron are lost daily due to mucosal and skin epithelial cell sloughing, so control of iron levels is mostly by regulating uptake.[34] Regulation of iron uptake is impaired in some people as a result of a genetic defect that maps to the HLA-H gene region on chromosome 6. In these people, excessive iron intake can result in iron overload disorders, such as hemochromatosis. Many people have a genetic susceptibility to iron overload without realizing it or being aware of a family history of the problem. For this reason, it is advised that people do not take iron supplements unless they suffer from iron deficiency and have consulted a doctor. Hemochromatosis is estimated to cause disease in between 0.3 and 0.8% of Caucasians.[35]

MRI finds that iron accumulates in the hippocampus of the brains of those with Alzheimer's disease and in the substantia nigra of those with Parkinson disease.[36]


Large amounts of ingested iron can cause excessive levels of iron in the blood. High blood levels of free ferrous iron react with peroxides to produce free radicals, which are highly reactive and can damage DNA, proteins, lipids, and other cellular components. Thus, iron toxicity occurs when there is free iron in the cell, which generally occurs when iron levels exceed the capacity of transferrin to bind the iron. Damage to the cells of the gastrointestinal tract can also prevent them from regulating iron absorption leading to further increases in blood levels. Iron typically damages cells in the heart, liver and elsewhere, which can cause significant adverse effects, including coma, metabolic acidosis, shock, liver failure, coagulopathy, adult respiratory distress syndrome, long-term organ damage, and even death.[37] Humans experience iron toxicity above 20 milligrams of iron for every kilogram of mass, and 60 milligrams per kilogram is considered a lethal dose.[38] Overconsumption of iron, often the result of children eating large quantities of ferrous sulfate tablets intended for adult consumption, is one of the most common toxicological causes of death in children under six.[38] The Dietary Reference Intake (DRI) lists the Tolerable Upper Intake Level (UL) for adults as 45 mg/day. For children under fourteen years old the UL is 40 mg/day.

The medical management of iron toxicity is complex, and can include use of a specific chelating agent called deferoxamine to bind and expel excess iron from the body.[37][39]

See also


  1. ^ "Iron and Nickel Abundances in H~II Regions and Supernova Remnants". June 14, 1995. Retrieved 2008-05-21. .
  2. ^ a b Walter H. Kohl (1995). Handbook of materials and techniques for vacuum devices. Springer. pp. 164–167. ISBN 1563963876. 
  3. ^ a b prepared under the direction of the ASM International Handbook Committee ; Howard Kuhn, Dana Medlin, volume editors. (2000). ASM Handbook – Mechanical Testing and Evaluation. 8. ASM International. p. 275. ISBN 0871703890. 
  4. ^ "Hardness Conversion Chart". Retrieved 2009-07-07. 
  5. ^ V. Raghavan (2004). Materials Science and Engineering. PHI Learning Pvt. Ltd.. p. 218. ISBN 8120324552. 
  6. ^ "Properties of Various Pure Irons : Study on pure iron I". Tetsu-to-Hagane 50 (1): 42–47. 
  7. ^ John Wilson Martin (2007). Concise encyclopedia of the structure of materials. Elsevier. p. 183. ISBN 0080451276. 
  8. ^ "Iron: geological information". Retrieved 2008-05-21. .
  9. ^ Dauphas, N. & Rouxel, O. (2006). "Mass spectrometry and natural variations of iron isotopes". Mass Spectrometry Reviews 25 (4): 515–550. doi:10.1002/mas.20078. PMID 16463281. 
  10. ^ The origins of Iron Working in India: New evidence from the Central Ganga plain and the Eastern Vindhyas by Rakesh Tewari (Director, U.P. State Archaeological Department)
  11. ^ E. Photos (1989). "The Question of Meteoritic versus Smelted Nickel-Rich Iron: Archaeological Evidence and Experimental Results". World Archaeology 20 (3): 403–421. 
  12. ^ Muhly, James D. 'Metalworking/Mining in the Levant' pp. 174-83 in Near Eastern Archaeology ed. S. Richard Winona Lake, IN: Eisenbrauns (2003): 180.
  13. ^ Donald B. Wagner (2003). "Chinese blast furnaces from the 10th to the 14th century". Historical Metallurgy 37 (1): 25–37.  originally published in Donald B. Wagner (2001). "Chinese blast furnaces from the 10th to the 14th century". West Asian Science, Technology, and Medicine 18: 41–74. 
  14. ^ a b Camp, James McIntyre; Francis, Charles Blaine (1920). The Making, Shaping and Treating of Steel. Pittsburgh: Carnegie Steel Company. pp. 173–174. 
  15. ^ "Classification of Carbon and Low-Alloy Steels". Retrieved 2008-01-05. 
  16. ^ Solid rocket boosters
  17. ^ Vivian Marx (2002). "The Little Plankton That Could…Maybe". Scientific American. 
  18. ^ Melinda Ferguson, David Labiak, Andrew Madden, Joseph Peltier. "The Effect of Iron on Plankton Use of CO2". CEM 181H. Retrieved 2007-05-05. 
  19. ^ Dopyera, Caroline (October 1996). "The Iron Hypothesis". EARTH. Retrieved 2007-05-05. 
  20. ^ Enthaler, Stephan; Junge, Kathrin; Beller, Matthias (2008). "Sustainable Metal Catalysis with Iron: From Rust to a Rising Star?". Angew. Chem. Int. Ed. 47: 3317. doi:10.1002/anie.200800012. 
  21. ^ Fox, B. A.; Threlfall, T. L. (1973), Org. Synth. 5: 346 
    Fox, B. A.; Threlfall, T. L. (1964), Org. Synth. 44: 34  Article
  22. ^ Blomquist, A. T.; Dinguid, L. I. (1947). "Benzothiazoles. II. Nuclear chlorination in the Herz process". J. Org. Chem. 12: 718. doi:10.1021/jo01169a005. 
  23. ^ Clarke, H. T.; Dreger, E. E. (1941), Org. Synth. 1: 304 
    Clarke, H. T.; Dreger, E. E. (1926), Org. Synth. 6: 52  Article
  24. ^ den Hertog, J.; Overhoff (1950). Recl. Trav. Chim. 69: 468. 
  25. ^ Nanami, M. et al. (2005). "Tumor necrosis factor-α-induced iron sequestration and oxidative stress in human endothelial cells". Arteriosclerosis, thrombosis, and vascular biology 25 (12): 2495–2501. doi:10.1161/01.ATV.0000190610.63878.20. 
  26. ^ Rouault, Tracey A. (2003). "How Mammals Acquire and Distribute Iron Needed for Oxygen-Based Metabolism". PLoS Biology 1 (1): e9. doi:10.1371/journal.pbio.0000079. PMID 14551907. 
  27. ^ Food Standards Agency - Eat well, be well - Iron deficiency
  28. ^ Sesink AL, Termont DS, Kleibeuker JH, Van der Meer R (1999). "Red meat and colon cancer: the cytotoxic and hyperproliferative effects of dietary heme". Cancer Research 59 (22): 5704. PMID 10582688. 
  29. ^ Glei M, Klenow S, Sauer J, Wegewitz U, Richter K, Pool-Zobel BL (2006). "Hemoglobin and hemin induce DNA damage in human colon tumor cells HT29 clone 19A and in primary human colonocytes". Mutat. Res. 594 (1-2): 162–71. doi:10.1016/j.mrfmmm.2005.08.006. PMID 16226281. 
  30. ^ Pineda O, Ashmead HD (2001). "Effectiveness of treatment of iron-deficiency anemia in infants and young children with ferrous bis-glycinate chelate". Nutrition 17 (5): 381–4. doi:10.1016/S0899-9007(01)00519-6. PMID 11377130. 
  31. ^ Ashmead, H. DeWayne (1989). Conversations on Chelation and Mineral Nutrition. Keats Publishing. ISBN 0-87983-501-X. 
  32. ^ "Dietary Reference Intakes: Elements" (PDF). The National Academies. 2001. Retrieved 2008-05-21. 
  33. ^ "Iron Deficiency Anemia" (web page). MediResource. Retrieved 2008-12-17. 
  34. ^ Kumar, Vinay; Abbas, Abul K; Fausto, Nelson (2005). "Anemia". Robbins and Cotran: Pathologic Basis of Disease, 7th edition. Elsevier Saunders. Retrieved 2008-03-14. 
  35. ^ Durupt S, Durieu I, Nove-Josserand R, et al. (2000). "Hereditary hemochromatosis". Rev Med Interne 21 (11): 961–71. doi:10.1016/S0248-8663(00)00252-6. PMID 11109593. 
  36. ^ Brar S, Henderson D, Schenck J, Zimmerman EA. (2009). Iron accumulation in the substantia nigra of patients with Alzheimer disease and parkinsonism. Arch Neurol. 66(3):371-4. PMID 19273756
  37. ^ a b Cheney K, Gumbiner C, Benson B, Tenenbein M (1995). "Survival after a severe iron poisoning treated with intermittent infusions of deferoxamine". J Toxicol Clin Toxicol 33 (1): 61–6. doi:10.3109/15563659509020217. PMID 7837315. 
  38. ^ a b "Toxicity, Iron". Emedicine. Retrieved 2006-06-19. 
  39. ^ Tenenbein M (1996). "Benefits of parenteral deferoxamine for acute iron poisoning". J Toxicol Clin Toxicol 34 (5): 485–9. doi:10.3109/15563659609028005. PMID 8800185. 


  • Doulias PT, Christoforidis S, Brunk UT, Galaris D. Endosomal and lysosomal effects of desferrioxamine: protection of HeLa cells from hydrogen peroxide-induced DNA damage and induction of cell-cycle arrest. Free Radic Biol Med. 2003;35:719-28.
  • H. R. Schubert, History of the British Iron and Steel Industry ... to 1775 AD (Routledge, London, 1957)
  • R. F. Tylecote, History of Metallurgy (Institute of Materials, London 1992).
  • R. F. Tylecote, 'Iron in the Industrial Revolution' in J. Day and R. F. Tylecote, The Industrial Revolution in Metals (Institute of Materials 1991), 200-60.

External links

1911 encyclopedia

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Definition from Wiktionary, a free dictionary

A pot of melted raw iron.



Wikipedia has an article on:


Etymology 1

The position of the element iron in the periodic table, and its structure.

From Middle English iren, a rhotacism of Old English īsern (also isærn, iren, isen). Cognate with Danish jern, Middle Dutch iser (Dutch ijzer), Frankish īsarn, Old Frisian isern, Old High German īsarn (also īsan), Middle High German īsern (also īsen) (German Eisen), Gothic 𐌴𐌹𐍃𐌰𐍂𐌽 (eisarn), Old Norse ísarn (also járn), Norwegian (Nynorsk) jarn, Norwegian (Bokmål) jern, Swedish järn, Old Saxon īsarn.

The word derives from the Proto-Germanic *īsarna-, which is most likely from the Proto-Celtic *isarnon (Old Irish iarn, Welsh haearn, haiarn), from the Proto-Indo-European *is-(e)ro- (powerful or holy), from the Proto-Indo-European *eis (strong). Cognate on that level to the Sanskrit इषिर (iṣirá), vigorous, strong) and the Greek ἱερός (hierós), strong). Possibly akin to the Latin ira (anger).

The pronunciation is due to metathesis.


Chemical element
Fe Previous: manganese (Mn)
Next: cobalt (Co)



countable and uncountable; plural irons

iron (countable and uncountable; plural irons)

An electric clothes iron.
  1. (uncountable, chemistry) A metallic chemical element having atomic number 26, and symbol Fe.
  2. (countable) A tool or appliance made of metal, which is heated and then used to transfer heat to something else; most often a thick piece of metal fitted with a handle and having a flat, roughly triangular bottom, which is heated and used to press wrinkles from clothing, and now usually containing an electrical heating apparatus.
  3. (usually plural, irons) Shackles.
  4. (slang) A handgun.
  5. (uncountable) A dark shade of the colour/color silver.
  6. (Cockney rhyming slang, shortened from iron hoof, rhyming with poof; countable, offensive) A male homosexual.
  7. (golf) A golf club used for middle-distance shots.
  • (shackles): leg irons
  • (golf club): driving iron, long iron, short iron, 1-iron, 2-iron, 3-iron, 4-iron, 5-iron, 6-iron, 7-iron, 8-iron, 9-iron,
  • (metallic chemical element): molecule (sometimes)
Coordinate terms
See also
Derived terms
Related terms
The translations below need to be checked and inserted above into the appropriate translation tables, removing any numbers. Numbers do not necessarily match those in definitions. See instructions at Help:How to check translations.


  • iron” in the Online Etymology Dictionary, Douglas Harper, 2001

Etymology 2



iron (comparative more iron, superlative most iron)


more iron

most iron

  1. (not comparable) Made of the metal iron.
  2. (figuratively) Strong (as of will), inflexible.
    She had an iron will.
    He held on with an iron grip.
  • (made of the metal iron): wrought-iron,
See also
Derived terms

Etymology 3

An extension of Etymology 1.



to iron

Third person singular

Simple past

Past participle

Present participle

to iron (third-person singular simple present irons, present participle ironing, simple past and past participle ironed)

  1. (transitive) To pass an iron over (clothing or some other item made of cloth) in order to remove creases.
  • (to pass an iron over): press
Coordinate terms
  • (to pass an iron over): mangle
Derived terms




iron (kanji 異論, hiragana いろん)

  1. objection, differing opinion

Bible wiki

Up to date as of January 23, 2010

From BibleWiki

Tubal-Cain is the first-mentioned worker in iron (Gen 4:22). The Egyptians wrought it at Sinai before the Exodus. David prepared it in great abundance for the temple (1Chr 22:3: 29:7). The merchants of Dan and Javan brought it to the market of Tyre (Ezek 27:19). Various instruments are mentioned as made of iron (Deut 27:5; 19:5; Josh 17:16, 18; 1Sam 17:7; 2 Sam 12:31; 2Kg 6:5, 6; 1Chr 22:3; Isa 10:34).

Figuratively, a yoke of iron (Deut 28:48) denotes hard service; a rod of iron (Ps 29), a stern government; a pillar of iron (Jer 1:18), a strong support; a furnace of iron (Deut 4:20), severe labour; a bar of iron (Job 40:18), strength; fetters of iron (Ps 10710), affliction; giving silver for iron (Isa 60:17), prosperity.

This entry includes text from Easton's Bible Dictionary, 1897.

what mentions this? (please help by turning references to this page into wiki links)

This article needs to be merged with IRON (Jewish Encyclopedia).

Simple English

This article is about iron the metal. For the tool called iron, see ironing.
A chunk of iron

Iron (Fe) is the most common metal on Earth. It is element 26, a transition metal in Group 8. Its symbol is Fe, from the Latin word for iron, Ferrum. Its atomic number is 26 and its mass number is 55.85.

It is used a lot because it is very strong and cheap. Iron is the main thing used to make steel. As iron is magnetic, it can be used to make a magnet.



Physical properties

Iron is a grey metal. It is magnetic. It is quite strong, which is why it is used. Very pure iron is soft, while steel (iron mixed with a little carbon) is harder. The more carbon is in iron, the harder it is.

Chemical properties

Iron is quite reactive. It reacts with most acids like sulfuric acid. It makes ferrous sulfate when reacted with sulfuric acid. This reaction with sulfuric acid is used to clean metal.

Iron reacts with air and water to make rust. The rust flakes off, making more iron rust. Eventually, the whole piece of iron is rusted away. Other metals like aluminum do not rust away.

Iron powder can react with sulfur to make iron(II) sulfide, a hard black solid. Iron also reacts with the halogens to make iron(III) halides, like iron(III) chloride. Iron reacts with the hydrohalic acids to make iron(II) halides like [[iron(II) chloride.

Chemical compounds

Iron makes chemical compounds with other elements. Normally the other element oxidizes iron. Sometimes two electrons are taken and sometimes three. Compounds where iron has two electrons taken are called ferrous compounds. Compounds where iron has three electrons taken are called ferric compounds. Ferrous compounds have iron in its +2 oxidation state. Ferric compounds have iron in its +3 oxidation state. Iron compounds can be black, brown, yellow, green, or purple.

Ferrous compounds are weak reducing agents. Many of them are green or blue. The most common ferrous compound is ferrous sulfate.

Ferric compounds are oxidizing agents. Many of them are brown. The most common ferric compound is ferric oxide, the same thing as rust. One reason why iron rusts is because ferric oxide is an oxidizing agent. It oxidizes iron, rusting it even under paint. That is why if there is a small scratch in the paint, the whole thing can rust.

Iron in the ground

Iron is hardly ever found in the earth. Sometimes rocks that fall from outer space have iron metal in them. Normally hematite is in the ground. The hematite is used to make iron metal.

Some iron is found in meat. Iron is also found in hemoglobin in blood. Not all blood has hemoglobin in it, though.

Making iron

File:Engelsberg blast
Blast furnace

Iron is made in large factories called ironworks by reducing hematite with carbon (coke). This happens in large containers called blast furnaces. The blast furnace is filled with iron ore, coke and limestone. A very hot blast of air is blown in, where it burns up the coke. The extreme heat makes the carbon react with iron ore, taking off the oxygen from iron oxides, and making carbon dioxide. There is normally some sand in with the iron. The limestone, which is made of calcium carbonate, turns into calcium oxide and carbon dioxide when very hot. The calcium oxide reacts with the sand to make a liquid called a slag. This is drained, leaving the iron. The reaction will leave pure liquid iron on the bottom of the blast furnace, where it can be shaped and hardened after cooling down. Almost all ironworks are today part of steel mills, and almost all iron is further processed into steel.

There are many ways to work iron. Iron can be hardened by heating a piece of metal and splashing it into cold water. It can be softened by heating it and allowing it to slowly cool. It can also be stamped by a heavy press. It can be pulled into wires. It can be rolled to make sheet metal.


As a metal

A bridge made out of iron

Iron is used more than any other metal. It is strong and cheap. It is used to make buildings, bridges, nails, screws, pipes, girders, and towers. Iron is magnetic, so it is used in many magnets.

Iron is used in nails because it is very strong. it is also very easy to get to. there is alot in the world so it is cheap.

There are different types of iron. Cast iron is iron made by the way described above in the article. It is hard and brittle. It is used to make things like storm drain covers, manhole covers, and engine blocks (the main part of an engine).

Steel is the most common form of iron. Steels come in several forms. Mild steel is steel with a little carbon. It is soft and easily bent, but it does not crack easily. It is used for nails and wires. Carbon steel is harder but more brittle. It is used in tools. There are other special types of steel. Stainless steel does not rust. Some other types of steel are very strong. Other types are very hard.

Wrought iron is easily shaped and used to make fences and chains.

Some iron is very pure. It just has iron in it. This iron is very soft and easily made into a magnet. It is made by electrolysis of iron(II) chloride solution. It is used in the core of an electromagnet.

As compounds

Iron compounds are used for several things. Iron(II) chloride is used to make water clean. Iron(III) chloride is also used. Iron(II) sulfate is used to reduce chromates in cement. Some iron compounds are used in vitamins.

Use in food

Our bodies need iron to help oxygen get to our muscles, because the molecule is at the heart of some essential macromolecules such as hemoglobin. Many cereals have some added iron (the element metal iron).[1][2] It is added to cereal in the form of tiny metal filings. It is even possible to see the slivers sometimes by taking an extremely strong magnet and putting it into the box. The magnet will attract these pieces of iron. Eating these small metal shavings are not harmful to our body. [3]

Iron is most available to the body when added to amino acids – iron in this form is ten to fifteen times more digestible than than it is as an element.[4] Iron is also found in meat, for example steak. Iron provided by diet supplements is in the form of a chemical, such as a sulphate, which is cheap and is absorbed well. The body will not take up more iron than it needs, and it usually needs very little. The iron in red blood cells is recycled by a system which breaks down old cells. Loss of blood by injury or parasite infection may be more serious.[5]


Iron is toxic when large amounts are swallowed. It can damage the body. When too many vitamins that have iron in them are eaten, sickness happens. There are chemicals that doctors have that can react with iron and stop it from poisoning people.

Other pages


  1. "Testing the Fortitude of Iron in Cereals". United States Department of Agriculture. Retrieved 2010-01-29. 
  2. Adams, Cecil. Return of the Straight Dope. New York: Ballantine Books, 1994
  3. Felton, Bruce. One of a Kind. New York: William Morrow and Co., 1992
  4. Pineda O, Ashmead HD (2001). [Expression error: Unexpected < operator "Effectiveness of treatment of iron-deficiency anemia in infants and young children with ferrous bis-glycinate chelate"]. Nutrition 17 (5): 381–4. doi:10.1016/S0899-9007(01)00519-6. PMID 11377130. 
  5. Andrews N.C. 2000. Disorders of iron metabolism. New England Journal of Medicine. Related correspondence, published in NEJM 342:1293-1294.



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