IRON [Fe]
Characteristics
An : 26
N : 30 A
m : 55.845 (2) g/mol
Group No : 8
Group Name : Transition metals
Block : d-block
Period : 4
State : solid at 298 K
Colour : lustrous, metallic, greyish tinge
Classification : Metallic
Boiling Point : 3034K (2861oC)
Melting Point : 1811K (1538oC)
Density : 7.86g/cm3
Availability : Iron is available in many forms including foil, chips, sheet, wire, granules, nanosized activated powder, powder, and rod. Small and large samples of iron foil, sheet and wire (also Iron alloy in foil form and stainless steel alloys in foil, sheet, wire, wire straight cut lengths, insulated wire, mesh, rod, tube and powder form).
Hematite is an important iron mineral. The specimen is from the Montreal Mine in Hurley, Michigan USA.
Discovery Information
Who : Known to the ancients.
The first iron used by mankind, far back in prehistory, came from meteors. Cast iron was first produced in China about 550 BC, but not in Europe until the medieval period.
Name Origin
Latin : ferrum (iron). "Iron" in different languages.
Sources
Obtained from iron ores. It makes up about 34% of the of the mass of the Earth’s crust. It is the most abundant heavy metal in the universe, the tenth most abundant element. Primary sources are China (around 25%), Brazil, Australia and India followed by the USA, Canada, Sweden, South Africa, Russia and Japan. Annual production in 2005 was 1.544 million tonnes.
magnetite is an important iron mineral. These octahedral magnetite crystals are from Cerro Huanaquino Potosi, Bolivia
Abundance
Universe : 1100 ppm (by weight)
Sun : 1000 ppm (by weight)
Carbonaceous meteorite : 2.2 x 105 ppm
Earth’s Crust : 63000 ppm
Seawater : Atlantic surface : 1 x 10-4 ppm; Atlantic deep : 4 x 10-4 ppm; Pacific surface : 1 x 10-5 ppm; Pacific deep : 1 x 10-4 ppm
Human : 60000 ppb by weight 6700 ppb by atoms
Uses
Used in steel and other alloys which are used in countless products. It is essential for animals as it is the chief constituent of hemoglobin which carries oxygen in blood vessels. Iron(III) oxides are used in the production of magnetic storage in computers. They are often mixed with other compounds, and retain their magnetic properties in solution.
History
The first iron used by mankind, far back in prehistory, came from meteors. The smelting of iron in bloomeries probably began in Anatolia or the Caucasus in the second millennium BC or the latter part of the preceding one. Cast iron was first produced in China about 550 BC, but not in Europe until the medieval period. 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 a 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.
Notes
Iron is the most used of all the metals, comprising 95 percent of all the metal tonnage produced worldwide. With the exception of a few bacteria, iron is essential to all living organisms.
Hazards
Iron dust may be harmful if inhaled.
Iron Compounds
Haemoglobin, C2952H4664N812O832S8Fe4
The iron-containing oxygen-transport metalloprotein in the red cells of the blood in mammals and other animals. Hemoglobin in vertebrates transports oxygen from the lungs to the rest of the body, such as to the muscles, where it releases the oxygen load. Hemoglobin also has a variety of other gas-transport and effect-modulation duties, which vary from species to species, and which in invertebrates may be quite diverse.
Iron(II) sulfate, FeSO4.H2O
In horticulture it is used as a lawn conditioner and moss killer, traditionally referred to as sulphate of iron. Ferrous sulfate is also used to treat iron-deficiency anemia. Side effects of therapy may include nausea and epigastric abdominal discomfort after taking iron. These side effects can be minimized by taking ferrous sulfate at bedtime. Ferrous sulfate can also be used to colour concrete. It is best used for newly cured concrete. Mix with water until saturated and spray onto concrete. The colour will range from yellow to rust.
Iron(III) chloride, FeCl3 [ Highly Corrosive & Toxic ]
Most widely used for etching copper in the production of printed circuit boards. Iron(III) chloride is also used as a catalyst for the reaction of ethylene with chlorine, forming ethylene dichloride (1,2-Dichloroethane), an important commodity chemical, which is mainly used for the industrial production of vinyl chloride, the monomer for making PVC. It is also commonly used by knife craftsmen and swordsmiths to stain blades, as to give a contrasting effect to the metal, and also to view metal layering or imperfections.
Iron(III) oxide, Fe2O3
Used in magnetic storage, for example in the magnetic layer of floppy disks. A very fine powder of ferric oxide is known as jeweller’s rouge, red rouge, or simply rouge. It is used to put the final polish on metallic jewellery and lenses, and historically as a cosmetic.
Reactions of Iron
Reactions with water
Air-free water has little effect upon iron metal. However, iron metal reacts in moist air by oxidation to give a hydrated iron oxide. This does not protect the iron surface to further reaction since it flakes off, exposing more iron metal to oxidation. This process is called rusting!
Reactions with air
Iron metal reacts in moist air by oxidation to give a hydrated iron oxide. This does not protect the iron surface to further reaction since it flakes off, exposing more iron metal to oxidation. This process is called rusting. Finely divided iron powder is pyrophoric, making it a fire risk. On heating with oxygen the result is formation of the iron oxides Fe2O3 and Fe3O4.
4Fe(s) + 3O2(g) --> 2Fe2O3(s)
3Fe(s) + 2O2(g) --> 2Fe3O4(s)
Reactions with halogens
Iron reacts with excess of fluorine, chlorine and bromine to form Fe(III) halides.
2Fe(s) + 3F2(g) --> 2FeF3(s)
2Fe(s) + 3Cl2(g) --> 2FeCl3(s)
2Fe(s) + 3Br2(g) --> 2FeBr3(s)
This reaction is not very successful for iodine because of thermodynamic problems. The iron(III) is too oxidizing and the iodide is too reducing. The direct reaction between iron and iodine can be used to prepare iron (II) iodide.
Fe(s) + I2(s) --> FeI2(s)
Reactions with acids
Iron metal dissolves readily in dilute sulphuric acid in the absence of oxygen to form solutions containing the aquated Fe(II) ion together with hydrogen gas.
Fe(s) + H2SO4(aq) --> Fe2+(aq) + SO42-(aq) + H2(g)
If oxygen is present, some of the Fe(II) oxidizes to Fe(III). The strongly oxidizing concentrated nitric acid, HNO3, reacts on th surface of iron and passivates the surface.
Occurrence and Production of Iron
Occurrence
Iron is one of the most common elements on Earth, making up about 5% of the Earth’s crust. Most of this iron is found in various iron oxides, such as the minerals hematite, magnetite, and taconite. The Earth’s core is believed to consist largely of a metallic iron-nickel alloy. 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’s red colour is thought to be an iron-oxide-rich soil.
Production
Industrially, iron is produced starting from iron ores, principally haematite (nominally Fe2O3) and magnetite (Fe3O4) by a carbothermic reaction (reduction with carbon) in a blast furnace at temperatures of about 2000oC. 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.
In the furnace, the coke reacts with oxygen in the air blast to produce carbon monoxide:
6C + 3O2 --> 6CO
The carbon monoxide reduces the iron ore (in the chemical equation below, hematite) to molten iron, becoming carbon dioxide in the process:
6CO + 2Fe2O3 --> 4Fe + 6CO2
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, 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 steel or commercially pure iron, known as wrought iron, using other furnaces or converters. In 2005, approximately 1,544Mt (million tons) of iron ore was produced worldwide. China was the top producer of iron ore with atleast one-fourth world share followed by Brazil, Australia and India, reports the British Geological Survey.
Isotopes of Iron
54Fe [28 neutrons]
Abundance : 5.8%
Half life : 3.1 x 1022 years [ Double Electron Capture ]
Decay Energy : ? MeV
Decays to 54Cr.
55Fe [29 neutrons]
Abundance : synthetic
Half life : 2.73 years [ Electron Capture ]
Decay Energy : 0231 MeV
Decays to 55Mn.
56Fe [30 neutrons]
Abundance : 91.72%
Stable with 30 neutrons
57Fe [31 neutrons]
Abundance : 2.2%
Stable with 31 neutrons
58Fe [32 neutrons]
Abundance : 0.28%
Stable with 32 neutrons
59Fe [33 neutrons]
Abundance : synthetic
Half life : 44.503 days
Decay Energy : 1.565 MeV
Decays to 59Co.
60Fe [34 neutrons]
Abundance : synthetic
Half life : 1.5 x 106 years [ beta- ]
Decay Energy : 3.978 MeV
Decays to 60Co.
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