Iron

Occurrence

Iron is believed to be the sixth [3] most taconite. About 5% of the meteorites similarly consist of iron-nickel alloy. Although rare, these are the major form of natural metallic iron on the earth's surface.

The reason for Mars' red colour is thought to be an iron-oxide-rich soil.

See also Iron minerals.  

Characteristics

Iron is a carbon. The many iron alloys, which have very different properties, are discussed in the article on steel.

Nuclei of iron 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, and iron abundance on Earth greatly favors iron over nickel, and also presumably in supernova element production.^[1] When a very large star contracts at the end of its life, internal pressure and temperature rise, allowing the star to produce progressively heavier elements, despite these being less stable than the elements around mass number 60, known as the "iron group". This leads to a supernova.

Iron (as Fe²⁺, ferrous ion) is a necessary trace element used by almost all living organisms, the only exceptions are a few prokaryotic organisms which live in iron-poor conditions (such as the lactobacilli in iron-poor milk) which use manganese for catalysis instead as well as organisms which use catalase.

Applications

Iron is the most used of all the metals, comprising 95% of all the metal tonnage produced worldwide. Its combination of low cost and high strength make it indispensable, especially in applications like automobiles, the hulls of large ships, and structural components for buildings. Steel is the best known alloy of iron, and some of the forms that iron can take include:

• steel.
• magnesium to alter the shape of graphite to spheroids, or nodules, vastly increasing the toughness and strength of the material.
• Carbon steel contains 2.0% silicon.
• Wrought iron contains less than 0.25% carbon.^[2] It is a tough, malleable product, but not as fusible as pig iron. If honed to an edge, it loses it quickly.^{[citation needed]} Wrought iron is characterised by the presence of fine fibers 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 does not have the same corrosion resistance but is cheaper and more widely available.
• tungsten, etc. They are used for structural purposes, as their alloy content raises their cost and necessitates justification of their use. 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.
• Iron(III) oxides are used in the production of magnetic storage media in computers. They are often mixed with other compounds, and retain their magnetic properties in solution.

The main drawback to iron and steel is that pure iron, and most of its alloys, suffer badly from oxygen or by sacrificial protection.

Iron is believed to be the critical missing nutrient in the ocean that limits the growth of plankton. Experimental iron fertilization of areas of the ocean using iron(II) sulfate has proven successful in increasing plankton growth.^[4][5][6] Larger scaled efforts are being attempted with the hope that iron seeding and ocean plankton growth can remove carbon dioxide from the atmosphere, thereby counteracting the greenhouse effect that is generally agreed by climatologists to cause global warming.^[7]

Iron compounds

Main article: Iron compounds

 

• Iron(III) acetate (Fe(C₂H₃O₂)₃ is used in the cloth.

• Iron(III) ammonium oxalate (Fe(NH₄)₃(C₂O₄)₄) is used in blueprints.

• Iron(III) arsenate (FeAsO₄) is used in insecticide.

• paints, as an additive in animal feed, and as an etching material for engravement, photography and printed circuits.

• Iron(III) chromate (Fe₂(CrO₄)₃) is used as a yellow pigment for paints and ceramic.

• Iron(III) hydroxide (Fe(OH)₃) is used as a brown rubber and in water purification systems.

• Iron(III) phosphate (FePO₄) is used in fertilizer and as an additive in human and animal food.

• Iron(II) acetate (Fe(C₂H₃O₂)₂ is used in the dyeing of fabrics and leather, and as a wood preservative.

• Iron(II) gluconate (Fe(C₆H₁₁O₇)₂) is used as a dietary supplement in iron pills.

• Iron(II) oxalate (FeC₂O₄) is used as yellow pigment for paints, plastics, glass and ceramic, and in photography.

• Iron(II) sulfate (FeSO₄) is used in water purification and sewage treatment systems, as a herbicide, as an additive in animal feed, in wood preservative and as an additive to flour to increase iron levels.

• Iron-Fluorine complex (FeF₆)^3- is found in solutions containing both Fe(III) ions and fluoride ions.

Historical aspects

Main article: History of ferrous metallurgy

  The first iron used by mankind, far back in prehistory, came from meteors. The charcoal was required as fuel.

wrought iron no longer being produced.

Production of iron from iron ore

Main article: Blast furnace

      Ninety percent of all mining of metallic ores is for the extraction of iron. Industrially, iron is produced starting from air is forced into the furnace at the bottom.

In the furnace,(hot/oven) the carbon monoxide:

2 CO

The carbon monoxide reduces the iron ore (in the carbon dioxide in the process:

3 CO₂

The flux is present to melt impurities in the ore, principally calcium oxide (quicklime):

CO₂

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

CaSiO₃

The slag melts in the heat of the furnace, which silicon dioxide would not have. In the bottom of the furnace, the molten slag floats on top of the more dense 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.

Pig iron is not pure iron, but has 4-5% carbon dissolved in it. This is subsequently reduced to wrought iron, using other furnaces or converters.

In 2005, approximately 1,544 Mt (million metric tons) of iron ore was produced worldwide. China was the top producer of iron ore with at least one-fourth world share followed by Brazil, Australia and India, reports the British Geological Survey.

Isotopes

Main article: Isotopes of iron

Naturally occurring iron consists of four isotopes: 5.845% of radioactive ⁵⁴Fe (half-life: >3.1×10²² years), 91.754% of stable ⁵⁶Fe, 2.119% of stable ⁵⁷Fe and 0.282% of stable ⁵⁸Fe. ⁶⁰Fe is an extinct half-life (1.5 million years).

Much of the past work on measuring the isotopic composition of Fe has centered on determining ⁶⁰Fe variations due to processes accompanying nucleosynthesis (i.e., meteorite studies) and ore formation. In the last decade however, advances in 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.^[8]

The 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 ⁵⁶Fe is much more easily produced from lighter nuclei in nuclear reactions, it is the endpoint of fusion chains inside extremely massive stars and is therefore common in the universe, relative to other metals.

In phases of the meteorites Semarkona and Chervony Kut a correlation between the concentration 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).

Iron in organic synthesis

The usage of iron metal filings in organic synthesis is mainly for the deoxygenation of amine oxides.^[12]

Iron in biology

 

Main article: Human iron metabolism

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.

In animals, plants, and fungi, iron is often incorporated into the esters).

Iron distribution is heavily regulated in mammals, partly because iron has a high potential for biological toxicity. 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.^[13]

Nutrition and dietary sources

Good sources of dietary iron include red meat, fish, poultry, lentils, beans, leaf vegetables, tofu, chickpeas, black-eyed peas, potatoes with skin, bread made from completely whole-grain flour, molasses, teff and farina. Iron in meat is more easily absorbed than iron in vegetables.^[14]

Iron provided by Blood donors are at special risk of low iron levels and are often advised to supplement their iron intake.

Regulation of iron uptake

Excessive iron can be toxic, because free ferrous iron reacts with 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.

Iron uptake is tightly regulated by the human body, which has no physiological means of excreting iron, so controls iron levels solely by regulating uptake. Although uptake is regulated, large amounts of ingested iron can cause excessive levels of iron in the blood, because high iron levels can cause damage to the cells of the gastrointestinal tract that prevents them from regulating iron absorption. High blood concentrations of iron damage cells in the heart, liver and elsewhere, which can cause serious problems, including long-term organ damage and even death.

Humans experience iron toxicity above 20 milligrams of iron for every 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.

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 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 should 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. ^[18]

The medical management of iron toxicity is complex, and can include use of a specific deferoxamine to bind and expel excess iron from the body.

Bibliography

• Los Alamos National Laboratory — Iron
• 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.
• Crystal structure of iron

References

See also

• magnesium is located
• Iron (metaphor)
• Iron Age
• Iron fertilization - Fertilization of oceans to stimulate phytoplankton growth
• Pelletizing - Process of creation of iron ore pellets
• Al-Hadid (Iron) in the Qur'an
• Specht Building - A historic landmark in Omaha, Nebraska utilizing an iron facade.
• Iron in mythologybe-x-old:Жалеза