Iron is a chemical element with the symbol Fe (from Latin: ferrum ) and the atomic number 26. This is the metal in the first transition series. It is the most common elemental mass on Earth, forming many of the outer and inner nuclei of the Earth. This is the fourth most common element in the Earth's crust. Its abundance in rocky planets like Earth is due to the abundant production by fusion in high-mass stars, where it is the last element to be produced with the release of energy before the collapse of a supernova, which scatters iron into space.
Like the other 8 groups of elements, ruthenium and osmium, iron exists in varying degrees of oxidation, -2 to 7, although 2 and 3 are the most common. The element of iron occurs in meteoroids and other low oxygen environments, but is reactive to oxygen and water. The newly emerging iron surface shimmers silver gray, but oxidizes in normal air to provide a hydrated iron oxide, commonly known as rust. Unlike metals that form passive oxide layers, the iron oxide occupies more volume than the metal and thus peels off, exposing new surfaces to corrosion.
Iron metal has been used since ancient times, although copper alloys, which have lower melting temperatures, were used earlier in human history. Pure iron is relatively soft, but can not be obtained by melting as it is significantly hardened and reinforced by impurities, especially carbon, from the melting process. Certain proportions of carbon (between 0.002% and 2.1%) produce steel, which may be up to 1000 times harder than pure iron. Rough iron is produced in blast furnaces, where the ore is reduced by coke to rough iron, which has a high carbon content. Further enhancements with oxygen reduce the carbon content to the correct proportions to make steel. Steel and iron alloys formed with other metals (alloy steel) are the most common industrial metals because they have a large number of desirable properties and iron-bearing stones abound.
Iron chemical compounds have many uses. Iron oxide mixed with aluminum powder can be ignited to make a thermite reaction, used in welding and purifying ore. Iron forms a binary compound with halogen and chalcogen. Among the organometallic compounds are ferrocene, the first sandwich compound is found.
Iron plays an important role in biology, forming complexes with molecular oxygen in hemoglobin and myoglobin; these two compounds are common oxygen transport proteins in vertebrates. Iron is also a metal in the active site of many important redox enzymes associated with cell respiration and oxidation and reduction in plants and animals. In adult humans males are about 3.8 grams of iron, and 2.3 grams in women, for whom iron is distributed in hemoglobin and throughout the body. Iron is an essential element in the metabolism of hundreds of proteins and enzymes involved in various body functions, such as oxygen transport, DNA synthesis, and cell growth.
Video Iron
Characteristics
Mechanical properties
The mechanical properties of iron and alloys can be evaluated using various tests, including Brinell test, Rockwell test and Vickers hardness test. The data on iron is so consistent that it is often used to calibrate measurements or to compare tests. However, the mechanical properties of iron are significantly influenced by the purity of the sample: pure, single iron crystals are actually softer than aluminum, and pure industrial-produced iron (99.99%) has 20-30 Brinell hardness. Increased carbon content will lead to a significant increase in hardness and tensile strength of iron. The maximum resistance of 65 R c is achieved with a carbon content of 0.6%, although alloys have low tensile strength. Because of the softness of the iron, it is much easier to work than the heavier ruthenium and osmium.
Because of its significance for the planet's core, the physical properties of iron at high pressure and temperature have also been studied extensively. A stable iron form under standard conditions may be subjected to pressures up to ca. 15 GPa before turning into a high-pressure form, as described in the next section.
Phase and allotropic diagram
Iron is an example of allotropy in metals. At least four allotropic forms of iron are known as?,?,?, And ?; at very high pressures and temperatures, some controversial experimental evidence exists for stable? stage.
When the molten iron cools past the freezing point of 1538 ° C, it crystallizes inward? allotrope, which has a cubic body-centered cubic structure (bcc). When it cools further up to 1394 Â ° C, it changes into its allotrope-allotropic, cubic-faced cubic (fcc), or austenite crystal structure. At 912 ° C and below, the crystal structure returns to bcc? -iron alotrope. Finally, at 770 ° C (Curie point, T c ) the order of iron magnets changes from paramagnetic to ferromagnetic. When it passes the Curie temperature, iron does not alter its structure, but "magnetic domain" appears, in which each domain contains an iron atom with a certain electronic spin. In non-magnetic iron, all electronic spins of atoms in a domain have the same axis orientation; However, electrons from neighboring domains have another orientation with reciprocal cancellation results and no magnetic field. In thermagneticised iron, electronic spins of domains are parallel and magnet effects are amplified. Although each domain contains billions of atoms, they are very small, about 10 micrometers. This is because two unpaired electrons in each iron atom are in d z 2 and d x 2 - y 2 orbital, which does not point directly to the nearest neighbor in the cubic lattice centered on the body and therefore it does not participate in metal bonds; thus, they can interact magnetically with each other so that their rotation is parallel.
At the pressure above about 10 GPa and temperatures a few hundred kelvin or less ,? -iron turns into a sealed hexagonal structure (hcp), also known as? -iron; higher temperatures? -phase also changed to? -iron, but do it at a higher pressure. The -phases, if any, will appear at a minimum pressure of 50 GPa and a minimum temperature of 1500 K and have a orthorombic hp or double structure. These high pressure phases of iron are important as an endmember model for the solid part of the planet's core. Core core Earth is generally regarded as iron-nickel alloy with? (or?) structure. Rather confusing, the term "? -iron" is sometimes also used to refer? -iron over the Curie point, when it changes from being ferromagnetic to paramagnetic, though the crystal structure is unchanged.
The experimental iron melting point is well defined for less than 50 GPa pressures. For greater pressure, research puts a liquid - triple point? - at different pressures with dozens of gigapascals and 1000Ã, K at the melting point. In general, computer simulations of molecular dynamics of iron smelting experiments and shock waves suggest higher melting points and steeper slopes of the melt curve than static experiments performed in diamond anvil cells. The melting and boiling points of iron, together with the enthalpy of atomization, are lower than the previous 3d elements from scandium to chromium, indicating the reduced contribution of 3d electrons to metal bonds because they are attracted more and more to the inert nuclei by the nucleus; However, they are higher than values ​​for earlier manganese elements because they have a half-full 3d sub-pixel and consequently d-electrons are not easily delocalized. This same trend appears for ruthenium but not osmium.
Isotope
The natural iron consists of four stable isotopes: 5,845% of 54 Fe, 91.754% of 56 Fe, 2.119% of 57 Fe and 0.282% of 58 Fe. From this stable isotope, only 57 Fe has a nuclear spin (- 1 / 2 ). Nuclide 54 Fe could theoretically have double electron capture to 54 Cr, but the process was never observed and only the lower limit of the half-life of 3.1ÃÆ' â € " <10 22 year has been set.
60 Fe is an extinct radionuclide in a long half-life (2.6 million years). It is not found on Earth, but its main decay product is its grandson, stable nuclide 60 Ni. Much of the previous work on the iron isotope composition has focused on the nukleosynthesis of 60 Fe through meteorite studies and ore formation. In the last decade, advances in mass spectrometry have enabled minute detection and quantification, naturally occurring variations in stable iron-isotope ratios. Much of this work is driven by Earth science communities and planets, although applications for biological and industrial systems are emerging.
In the meteorite phase Semarkona and Chervony Kut, the correlation between the 60 concentration of Ni, the supernatural 60 Fe, and the abundance of isotopes steady iron provides evidence of the presence of 60 Fe at the time of formation of the Solar System. Perhaps the energy released by the decay of 60 Fe, together with those released by 26 Al, contributed to the re-widening and differentiation of asteroids after their formation 4.6 billion years ago. The abundance of 60 Ni in space material can bring further insight into the origin and early history of the Solar System.
The most abundant iron isotope 56 Fe is particularly attractive to nuclear scientists because it represents the most common nucleosynthesis endpoints. Because 56 Ni (14 alpha particles) is easily generated from lighter nuclei in the alpha process in nuclear reactions in supernovae (see silicon burning process), this is the end point of the fusion chain inside a very massive star, because the addition of other alpha particles, yields 60 Zn, requires more energy. 56 This Ni, which has a half-life of about 6 days, is made in quantity in these stars, but soon decays by two successive positron emissions in the supernova decay product in the supernova cloud gas residue, first to radioactive 56 Co, and then to stable 56 Fe. Thus, iron is the most abundant element in the red giant nucleus, and is the most abundant metal in iron meteorites and in solid metal cores such as Earth. This is also very common in the universe, relative to other stable metals with approximately the same atomic weight. Iron is the sixth most abundant element in the universe, and the most common refractory element.
Although a further small energy gain can be extracted by synthesizing 62 Ni, which has a slightly higher binding energy than 56 Fe, the star's condition is not suitable for this process. The elemental production in supernovae and distribution on Earth strongly supports iron over nickel, and in any case, 56 Fe still has a lower mass per nucleon than 62 Ni because the fraction higher proton lighter. Therefore, heavier elements of iron require a supernova for its formation, which involves catching fast neutrons by starting the core 56 Fe.
In the distant future of the universe, assuming that proton decay does not occur, the cold fusion that occurs through the quantum tunnel will cause the core of light in ordinary matter to merge into a 56 atomic nucleus. The fission and emission of alpha particles will make the nuclear decay to iron, converting all the mass of stars into cold spheres of pure iron.
Genesis
The original metal or iron is rarely found on the surface of the earth as it tends to oxidize, but the oxides are pervasive and represent the main ore. While it makes up about 5% of the Earth's crust, both the inner and outer core are believed to be composed mostly of nickel-iron alloys that constitute 35% of the Earth's overall mass. Iron is the most abundant element on Earth, but only the fourth most in the Earth's crust, after oxygen, silicon, and aluminum. Most of the iron in the crust is found in combination with oxygen as an iron oxide mineral such as hematite (Fe 2 O 3 ), magnetite (Fe 3 O 4 ), and siderite (FeCO 3 ). Many igneous rocks also contain pyrrhotite and pentlandite sulfite minerals.
Ferropericlase (Mg, Fe) O, periclase solid solutions (MgO) and wÃÆ'¼stite (FeO), form about 20% of the Earth's lower mantle volume, making it the second most abundant mineral phase in the region. after perovskite silicates (Mg, Fe) SiO 3 ; it is also the main host for iron in the lower mantle. At the bottom of the mantle transition zone, the reaction? (Mg, Fe) 2 [SiO 4 ] <-> (Mg, Fe) [SiO 3 ] (Mg, Fe) O transform? -olivin into a mixture of perovskite and ferropericlase and vice versa. In the literature, the mineral phase of the lower mantle is also often called magnesiowati. Perovskite silicates can form up to 93% of the lower mantle, and the magnesium iron form, (Mg, Fe) SiO 3 , is considered the most abundant mineral on Earth, forming 38% of its volume.
Large iron deposits are found in iron formations. This geologic formation is a type of rock consisting of a thin layer of recurrent iron oxide alternating with a shale ribbon and an iron-poor seepage. The banded iron formation was put in time between 3.700 million years ago and 1,800 million years ago .
The mentioned iron compounds have been used as pigments (compare ocher) since historical times and also contribute to the color of various geological formations, eg Buntsandstein (British Bunter, colored sandstones). In the case of Eisensandstein (jurassic iron sandstone ', eg from Donzdorf) in Germany and Bath stones in England, iron pigments contribute to the yellowish color of a large number of historic buildings and sculptures. The proverbial red color of the Martian surface comes from a rich iron oxide regolith.
Significant amounts of iron occur in iron sulphide pyrite (FeS 2 ), but it is difficult to extract the iron from it and is therefore not used. In fact, iron is so common that production generally focuses only on very high amounts of ore. During weathering, iron tends to absorb from sulphide deposits as sulfates and from silicate deposits as bicarbonate. Both are oxidized in aqueous solution and settle in even a slightly increased pH such as iron (III) oxide.
Approximately 1 in 20 meteorites comprise unique minerals of nickel-taenite (35-80% iron) and kamacite (90-95% iron). Although rare, iron meteorite is the main form of natural metallic iron on the surface of the earth. According to the report of the International Resource Panel of Metal Stocks in Society, global iron stocks used in the community are 2200 kg per capita. The more developed countries differ in this case from less developed countries (7000-14000 vs 2000Ã, kg per capita).
Maps Iron
Chemicals and compounds
Iron shows the characteristic chemical properties of transition metals, ie the ability to form oxidation variables stating differently with step one and very large coordination and organometallic chemistry: indeed, it is the invention of iron compounds, ferrocene, which revolutionized the last field in the 1950s. Iron is sometimes considered a prototype for the entire transition metal block, due to the abundance and large role that has been played in the advancement of humanity technology. The 26 electrons are arranged in the configuration of [Ar] 3d 6 4s 2 , in which 3d and 4s electrons are relatively close in energy, and thus they can lose the number of electrons and there is no clear point where further ionization becomes unprofitable.
Iron forms a compound mainly in 2 and 3 oxidation numbers. Traditionally, iron (II) compounds are called iron, and iron (III) iron compounds. Iron also occurs at higher levels of oxidation, eg. purple potassium ferrate (K 2 FeO 4 ), which contains iron in its 6 oxidation state. Although iron (VIII) oxide (FeO 4 ) has been claimed, the report can not be reproduced and such species (at least with iron under oxidation state 8) have been found to be unlikely computations.. However, one of the anionic forms of [FeO 4 ] - with iron in its oxidation state 7, together with iron (V) -isoxide isomer, has been detected by infrared spectroscopy at 4 K after coarse Fe atom atoms with a mixture of O 2 /Ar. Iron (IV) is a common intermediary in many biochemical oxidation reactions. Many organoiron compounds contain a formal oxidation state of 1, 0, -1, or even -2. The oxidation state and other bonding properties are often assessed using the MÃÆ'¶ssbauer spectroscopy technique. Many valence compound compounds contain iron (II) and iron (III) centers, such as magnetite and blue Prussia (Fe 4 (Fe [CN] 6 ) 3 ). The latter is used as a traditional "blue" blueprint.
Iron is the first transition metal that can not reach its group oxidation level 8, although its ruthenium and osmium may be harder, with ruthenium more difficult than osmium. Ruthenium shows aqueous cationic chemistry in a low oxidation state similar to iron, but osmium does not support high oxidation states in which it forms an anionic complex. In the second half of the 3d transition series, the vertical similarity under the group competes with the horizontal similarity of iron with its cobalt and nickel neighbors in the periodic table, which is also ferromagnetic at room temperature and share similar chemistry. Thus, iron, cobalt, and nickel are sometimes grouped together as iron triads.
The iron compounds produced at the largest scale in the industry are iron (II) sulfate (FeSO 4 Ã, Â · 7H 2 O) and iron (III) chloride (FeCl 3 ). The first one is one of the most available iron sources (II), but is less stable to air oxidation than the Mohr (NH 4 ) 2 Fe (SO 4 ) 2 Ã, Â · 6H 2 O). The iron (II) compounds tend to be oxidized to iron (III) compounds in the air.
Unlike many other metals, iron does not form amalgam with mercury. As a result, mercury is traded in a standard 76 pound bottle (34 kg) made of iron.
Iron is by far the most reactive element in its group; it is pyrophoric when divided subtly and easily soluble in dilute acid, giving Fe 2 . However, it does not react with concentrated nitric acid and other oxidizing acids due to the formation of resistant oxide layers, which however can react with hydrochloric acid.
Binary compound
The iron reacts with oxygen in the air to form various oxide and hydroxide compounds; the most common are iron (II, III) oxide (Fe 3 O 4 ), and iron (III) oxide (Fe 2 O < sub> 3 ). Iron (II) oxide also exists, although it is unstable at room temperature. Despite their name, they are in fact all non-stoichiometric compounds whose composition may vary. This oxide is the main ore for iron production (see bloomery and blast furnace). They are also used in the production of ferrite, useful magnetic storage media in computers, and pigments. The best known sulphide is pyrite iron (FeS 2 ), also known as stupid gold because of its sheen of gold. This is not an iron (IV) compound, but is actually an iron (II) polysulfide containing Fe 2 and 2 -
2 ions in a distorted sodium chloride structure.
The iron and iron binary halides are well known, with the exception of iron iodide. The iron halides usually arise from treating the ferrous metals with the corresponding hydrofic acid to provide suitable hydrated salts.
- Fe 2 HX -> FeX 2 H 2 (X = F, Cl, Br, I)
Iron reacts with fluorine, chlorine, and bromine to provide the corresponding iron halide, the most commonly used iron chloride.
- 2 Fe 3 2 -> 2 FeX 3 (X = F, Cl, Br)
Ferric iodide is an exception, which is thermodynamically unstable due to the oxidizing power of Fe 3 and high reduction power I - :
- 2 I - 2 Fe 3 -> I 2 2 Fe 2 (E < soup> 0 = 0.23 V)
However, the number of milligrams of iron iodide, black solids, can still be prepared through iron pentacarbonyl reactions with iodine and carbon monoxide in the presence of hexane and light at -20 ° C, ensuring that the system is also covered from air and water.
Chemical solutions
The standard reduction potential in aqueous solutions of acids for some common iron ions is given below:
Anion tetrahedral red ferrite (VI) is a strong oxidizing agent that oxidizes nitrogen and ammonia at room temperature, and even water itself in acidic or neutral solutions:
- 4 FeO 2 - 4 10 H
Ion Fe 3 has a great simple cationic chemical, although the hexaquo pale-violet ion [Fe (H 2 O) 6 ] 3 is easily hydrolyzed when the pH rises above 0 as follows:
When the pH rises above the yellow hydrolyzed species form above and when it rises above 2-3, the reddish hydro-brown iron (III) oxide precipitates out of the solution. Although Fe 3 has a configuration of
5 , its absorption spectrum is not like Mn 2 with a weak dd band, because Fe 3 has a higher positive charge and more polarization, decreasing the energy of the transfer absorption of its ligand-to-metal charge. Thus, all of the above complexes are somewhat strongly colored, with the sole exception of hexaquo ions - and even those that have a spectrum dominated by charge transfers in the near ultraviolet region. On the other hand, pale green iron (II) hexaquo ions 6 ] 2 do not have enough hydrolysis. Carbon dioxide did not evolve when carbonate anions were added, which produced white white (II) carbonates deposited outward. In excess of carbon dioxide it forms a slightly soluble bicarbonate, which generally occurs in groundwater, but is rapidly oxidized in the air to form iron (III) oxide that accounts for the large amount of chocolate deposits present.Coordinate compound
Many iron coordination compounds are known. The typical six-coordinate anions are hexachloroferrate (III), [FeCl 6 ] 3 - , found in a mixed salt of tetrakis (methylammonium) hexachloroferrate (III) chloride. Complexes with many bidentate ligands have geometric isomers. For example, trans -chlorohydridobis (bis-1,2- (diphenylphosphino) ethane) iron (II) complex is used as the starting material for the compound with Fe (dppe) 2 part. The ferrioxalate ion with three oxalate ligands (shown on the right) features a helical chiral with two non-superposabel geometries labeled ? (lambda) for the left-handed screw axis and ? (delta) for the right axis of the thread, in accordance with the IUPAC convention. Potassium ferrioxalate is used in chemical actinometry and along with its sodium salt undergoes photoreduction applied in old-style photographic processes. Dihydrate of iron (II) oxalate has a polymer structure with oxalative oxalate ions which bridges between the iron centers with the crystallized water located to form the lid of each octahedron, as illustrated below.
Blue prussia, Fe 4 [Fe (CN) 6 ] 3 , is the most famous of the iron cyanide complex. This formation can be used as a simple wet chemical test to distinguish between water solutions of Fe 2 and Fe 3 as they react (each) with potassium ferricyanide and potassium ferrocyanide to form blue Prussia.
The iron (III) complex is very similar to chromium (III) with the exception of iron preference (III) for O -oror instead of N -take out the ligand. The latter tend to be somewhat more unstable than iron (II) complex and often dissociate in water. Many Fe-O complexes exhibit intense colors and are used as tests for phenol or enol. For example, in an iron chloride test, used to determine the presence of phenol, iron (III) chloride reacts with phenol to form a deep violet complex:
- 3 ArOH FeCl 3 -> Fe (OAr) 3 3 HCl (Ar = aryl)
Among the halide and pseudohalide complexes, fluoro fluorine (III) complexes are the most stable, with [FeF 5 colorless (H 2 O)] 2- becomes the most stable aqueous solution. Chloro complex is less stable and supports tetrahedral coordination as in [FeCl 4 ] - ; [FeBr 4 ] - and [FeI 4 ] - are reduced easily to iron (II). Tiocyanate is a common test for the presence of iron (III) because it forms red blood [Fe (SCN) (H 2 O) 5 ] 2 . Like manganese (II), most of the iron (III) complexes are high spins, exceptions are those with high ligands in spectrochemical series such as cyanide. An example of a low-spin iron (III) complex is [Fe (CN) 6 ] 3 - . The cyanide ligand can easily be detached in [Fe (CN) 6 ] 3 - , and therefore this complex is toxic, unlike the iron (II) [Fe (CN) 6 ] 4 - is found in Prussian blue, which does not release hydrogen cyanide unless a dilute acid is added. Iron shows a large number of electronic rotation states, including any possible spin quantum number values ​​for block elements d from 0 (diamagnetic) to 5 / 2 ( 5 unpaired electrons). This value is always half of the number of unpaired electrons. Complexes with zero to two unpaired electrons are considered low spins and those with four or five are considered to be high spins.
The iron (II) complex is less stable than the iron (III) complex but the preference for O -the ligand is less marked, so eg [Fe (NH 3 ) 6 ] 2 is known when [Fe (NH 3 ) 6 ] 3 is not. They have a tendency to be oxidized to iron (III) but these can be moderated by the low pH and specific ligands used.
Organometallic compound
The cyanide complex is technically organologally but more importantly is the carbonyl and sandwich complexes and the half-sandwich compound. The main iron compound (0) is pentacarbonyl iron, Fe (CO) 5 , which is used to produce carbonyl iron powder, a highly reactive form of ferrous metal. Thermolysis pentacarbonyl iron provides trinuklear, triiron dodecacarbonyl. Collman reagents, disodium tetracarbonylferrate, are useful reagents for organic chemistry; contains iron in the oxidation state -2. Cyclopentadienyliron dicarbonyl dimer contains iron in a rare oxidation state 1.
Ferrocene is a very important compound in the early history of the branch of organometallic chemistry, and to date iron is still one of the most important metals in the art. It was first synthesized in 1951 during attempts to prepare fulvalene (C 10 H 8 ) by the oxidative dimerization of cyclopentadiene; the resulting product was found to have a formula of 10 H 10 Fe and reportedly showed "remarkable stability". This discovery sparked a substantial interest in the field of organometallic chemistry, in part because the structure proposed by Pauson and Kealy (shown on the right) is inconsistent with existing bonding models and does not explain unexpected stability. Consequently, the initial challenge is to definitively determine the structure of ferrocene in the hope that the bond and its nature will then be understood. The surprising new sandwich structure, [Fe ( 5 -C 5 H 5 ) 2 ], is inferred and was reported independently by three groups in 1952: Robert Burns Woodward and Geoffrey Wilkinson investigated the reactivity to determine the structure and showed that ferrocene undergoed a reaction similar to a typical aromatic molecule (such as benzene), Ernst Otto Fischer concluded the sandwich structure and also began to synthesise the metallocene others include cobaltocene; Eiland and Pepinsky confirmed the X-ray crystallography of the sandwich structure.
Applying the valence bond theory to ferrocene by considering the Fe 2 2 center and two cyclopentadienide anions (C 5 H 5 - ) , known as aromatic according to the HÃÆ'¼ckel rule and hence very stable, allowing correct prediction of molecular geometry. Once the molecular orbital theory was successfully applied and the Dewar-Chatt-Duncanson model was proposed, the reasons for the extraordinary stability of ferrocene became apparent. Ferrocene is not the first known organometallic compound - Zeise salt, K [PtCl 3 (C 2 H 4 )] Ã, Â · H 2 O was reported in 1831 and the discovery of Mond Ni (CO) 4 occurred in 1888, but the invention of ferrocene initiated organometallic chemistry as a separate chemical area. It is important that Wilkinson and Fischer share the 1973 Nobel Prize in Chemistry "for their pioneering work, conducted independently, on the chemistry of organometallic compounds, called sandwich compounds". Ferrocene alone can be used as the backbone of ligands, such as 1,1'-bis (diphenylphosphino) ferrocene (dppf). Ferrocene alone can be oxidized to ferrocium cation (Fc ); ferrocene/ferrocenium pairs are often used as references in electrochemistry.
Metallocenes such as ferrocene can be prepared by a newly cracked cyclopentadiene reaction with iron (II) chloride and base. It is an aromatic substance and undergoes a substitution reaction rather than an adduct reaction in the cyclopentadienyl ligand. For example, Friedel-Crafts acylation of ferrocene with acetic anhydride produces acetylferrocene as acyl benzene produces acetophenone under the same conditions.
Iron-centered organometallic species are used as catalysts. The KnÃÆ'¶lker complex, for example, is a transfer hydrogenation catalyst for ketones.
Etymology
As iron has been used for a long time, it has many different names in different languages. The source of the chemical symbol Fe is the Latin ferrum , and its derivatives are the names of elements in Roman (for example, French fer , Spanish < i> hierro , and Italian and Portuguese ferro ). The word ferrum itself may be derived from the Semitic, through Etruscan, from the root that also brings the old English brÃÆ'Â|s "brass". The English word iron comes primarily from Proto-Germanic * isarnan , which is also the source of the German name Eisen . It is most likely borrowed from Celtic isarnon , which eventually comes from Proto-Indo-Europe * is - (e) ro - "strong, sacred" and finally > * eis "strong", referring iron strength as metal. Kluge associates * isarnon with Illyric and Latin ira , 'wrath'). Balto-Slavic name for iron (eg, Russian ?????? [ zhelezo ], Polish Elazo , Lithuanian gele? is ) is the only one that comes directly from Proto-Indo-Europe * g h elg h - " iron". In many of these languages, the word for iron can also be used to denote other objects made of iron or steel, or figuratively because of the hardness and strength of the metal. The Chinese ti? (traditional ?; simplified?) Derived from Proto-Sino-Tibetan * hliek , and borrowed into Japanese as? tetsu , which also has native reading of kurogane "black metal" (similar to how iron is referenced in the word blacksmith in English).
History
Wrought iron
Iron is one element that is undoubtedly known in the ancient world. It has worked, or worked, for thousands of years. However, very old iron objects are much rarer than objects made of gold or silver because of the ease of rusted iron.
Beads made of meteoric iron in 3500 BC or previously found in Gerzah, Egypt by G. A. Wainwright. The beads contain 7.5% nickel, which is a signature of meteoric origin because iron found in the earth's crust generally contains only a small amount of nickel impurities. Meteoric iron is highly prized for its origin in the sky and is often used to forge weapons and equipment. For example, a dagger made of meteoric iron was found in Tutankhamun's tomb, which contained the same proportions of iron, cobalt, and nickel as the meteorites found in the area, stored by ancient meteor showers. The items possibly made of iron by Egyptians date from 3000 to 2500 BC. Meteorite iron is fairly soft and ductile and easily forged with cold work but can get brittle when heated because of the nickel content.
The first iron production began in the Middle Bronze Age but it took several centuries before the bronze iron was removed. The melted iron samples from Asmar, Mesopotamia and Tall Chagar Bazaar in northern Syria were made between 3000 and 2700 BC. The Hittites established the empire in north-central Anatolia around 1600 BC. They seem to be the first to understand the production of iron from the ore and consider it high in their society. The Hittites began to smell iron between 1500 and 1200 BC and practice spread throughout the Near East after their empire fell in 1180 BC. The next period is called the Iron Age.
The melted iron artifacts are found in India dating from 1800 to 1200 BC, and in Levant from about 1500 BC (suggesting smelting in Anatolia or Caucasus). The alleged reference (comparing the history of metallurgy in South Asia) to iron in the Vedic India has been used to claim the very early use of iron in India respectively to the present texts. The term rigveda ayas (metal) may refer to copper and bronze, while iron or ? Y? Ma ayas , literally "black metal", first mentioned in the post. Atharvaveda rigvedic.
Some archaeological evidence suggests iron was melted in Zimbabwe and southeastern Africa in the early 8th century BC. The work of iron was introduced to Greece in the late 11th century BC, which spread rapidly throughout Europe.
The spread of ironworking in Central and Western Europe is associated with Celtic expansion. According to Pliny the Elder, the use of iron was common in the Roman era. The annual iron production of the Roman Empire was estimated 84750 t, while the equally densely populated and contemporary Han Chinese produced around 5000 t. In China, iron only appears around 700-500 BC. Iron smelting may have been introduced to China through Central Asia. The earliest evidence of the use of blast furnaces in China dates from the 1st century, and cupola furnaces were used at the beginning of the Warring States (403-221 BC). The use of blast furnace and cupola remained widespread during the Song and Tang Dynasties.
During the Industrial Revolution in England, Henry Cort began to purify iron from rough iron to wrought iron (or iron bars) using an innovative production system. In 1783 he patented the process of lubrication for the purification of iron ore. It was later repaired by others, including Joseph Hall.
Cast iron
Cast iron was first produced in China during the 5th century BC, but hardly in Europe until the medieval period. The earliest cast iron artefacts discovered by archaeologists in the present area are Luhe County, Jiangsu in China. Cast iron is used in ancient China for war, agriculture, and architecture. During the medieval period, tools were found in Europe to produce wrought iron from cast iron (in this context known as rough iron) using wrought iron. For all these processes, char is required as fuel.
The explosion of medieval planting is about 10 feet (3.0 m) tall and made of refractory brick; forced air is usually provided by hand operated bellows. The modern blast furnace has grown much larger, with a fourteen-meter diameter stove that lets them produce thousands of tons of iron every day, but basically operates in the same way as they did during the middle ages.
In 1709, Abraham Darby I set up a coke furnace furnace to produce cast iron, replacing charcoal, although it continued to use blast furnace. The subsequent availability of cheap iron is one of the factors that led to the Industrial Revolution. Towards the end of the 18th century, cast iron began to replace wrought iron for a particular purpose, because the price was cheaper. Carbon content in iron was not involved as a reason for differences in the properties of wrought iron, cast iron, and steel until the 18th century.
Because iron became cheaper and more numerous, it also became the main structural material after the construction of the first innovative iron bridge in 1778. This bridge still stands today as a monument to the iron role played in the Industrial Revolution. After this, iron is used in rails, ships, boats, waterways, and buildings, as well as in iron cylinders in steam engines. Trains have been central to the formation of modernity and the ideas of progress and languages ​​(eg France, Spain, Italy, and Germany) refer to trains as iron roads.
Steel
Steel (with carbon content less than rough iron but more than wrought iron) was first produced in ancient times using bloomery. Blacksmiths in Luristan in western Persia were making good steel at 1000 BC. Later versions were upgraded, Wootz steel by India and Damascus steel developed around 300 BC and AD 500 respectively. These methods were special, so steel did not become a major commodity until the 1850s.
The new method for producing it with carburizing iron rods in a cementation process was designed in the 17th century. In the Industrial Revolution, the new method produced a barged carbon bar without being designed and this was then applied to produce steel. In the late 1850s, Henry Bessemer invented a new steelmaking process, which involved blowing air through molten pig iron, to produce mild steel. This makes steel much more economical, thus causing wrought iron to no longer be produced in large quantities.
The modern chemical foundation
In 1774, Antoine Lavoisier used a water vapor reaction with metallic iron in an incandescent iron tube to produce hydrogen in his experiments leading to a demonstration of conservation of mass, which was instrumental in transforming chemistry from qualitative science to quantitative.
The symbolic role
Iron plays a certain role in mythology and has found various uses as metaphors and in folklore. The Greek poet Hesiod's Works and Days (line 109-201) lists various human ages named after metals such as gold, silver, bronze and iron to explain the human age in a row. The iron age is closely related to Rome, and in Ovid's Metamorphoses
Virtue, despair, stop from the earth; and the depravity of man becomes universal and complete. So hard steel works.
An example of the importance of iron symbolic role can be found in the German Campaign of 1813. Frederick William III commissioned the first Iron Cross as a military decoration. Berlin iron jewelry reached the peak of production between 1813 and 1815, when the Prussian royal family urged residents to donate gold and silver jewelry for military funding. The inscription Gold gab ich fÃÆ'¼r Eisen (I gave gold to iron) was also used in the war effort then.
Metallic iron production
Industrial route
Iron or steel production is a process consisting of two main stages. In the first stage, the crude iron is produced in a blast furnace. Or, maybe directly reduced. In the second stage, pig iron is converted into wrought iron, steel, or cast iron.
For some limited purposes when needed, pure iron is produced in small quantities by reducing pure oxide or hydroxide with hydrogen, or forming pentacarbonyl iron and heating it to 250 ° C so it breaks down to form pure iron. powder. Another method is the electrolysis of iron chloride to the iron cathode.
Blast furnace processing
Industrial iron production starts with iron ore, especially hematite, which has the nominal formula Fe 2 O 3 , and magnetite, with the formula Fe 3 O < sub> 4 . This ore is reduced to metals in a carbothermic reaction, ie by treatment with carbon. Conversion is usually performed in blast furnaces at temperatures of about 2000 ° C. Carbon is provided in the form of coke. The process also contains fluxes such as limestone, which is used to remove silicaceous minerals in the ore, which otherwise would clog the furnace. Cokes and limestone are inserted into the top of the furnace, while a massive explosion of air is heated to 900 ° C, about 4 tons per ton of iron, forced into the furnace at the bottom.
In the furnace, the coke reacts with oxygen in the air blast to produce carbon monoxide:
- 2 C O 2 -> 2 CO
Carbon monoxide reduces iron ore (in the chemical equation below, hematite) into molten iron, into carbon dioxide in the process:
- Fe 2 O 3 3 CO -> 2 Fe 3 CO 2
Some iron in the lower temperature areas lower than the furnace reacts directly with the coke:
- 2 Fe 2 O 3 3 C -> 4 Fe 3 CO 2
The fluxes present to dilute the impurities in the ore are mainly limestone (calcium carbonate) and dolomite (calcium-magnesium carbonate). Other special fluxes are used depending on ore detail. In hot furnaces the limestone flux decomposes into calcium oxide (also known as lime):
- CaCO 3 -> CaO CO 2
Then calcium oxide combines with silicon dioxide to form a molten slag.
- CaO SiO 2 -> CaSiO 3
The slag melted in the heat of the stove. At the bottom of the furnace, molten slag floats on a denser melting iron, and a hole at the side of the stove is open to run iron and slag separately. The iron, once cooled, is called pig iron, while the slag can be used as an ingredient in road construction or to repair poor soil minerals for agriculture.
Direct iron reduction
Due to environmental concerns, alternative methods of iron treatment have been developed. "Direct iron reduction" reduces iron ore to iron called "sponge" iron or "direct" iron suitable for steel making. The two main reactions consist of a direct reduction process:
Natural gas is oxidized in part (by heat and catalyst):
- 2 CH 4 O 2 -> 2 CO 4 H 2
These gases are then treated with iron ore in the furnace, producing solid sponge iron:
Silica is removed by adding lime flux as described above.
Thermite
Iron is a by-product of burning a mixture of aluminum powder and rust powder.
- Fe 2 O 3 2 Al -> 2 Fe Al 2 O 3
Further process
Iron pigs are not pure iron, but have 4-5% carbon dissolved in them with a small amount of other impurities such as sulfur, magnesium, phosphorus and manganese. Because carbon is the main impurities, iron (pig iron) becomes brittle and hard. Releasing other impurities produces cast iron, which is used to drill items in foundries such as stoves, pipes, radiators, lamp posts and rails.
Alternatively, pig iron can be made into steel (with about 2% carbon) or wrought iron (pure commercial iron). Various processes have been used for this, including forging putty, lubrication furnace, Bessemer converter, open fireplace furnace, basic oxygen furnace, and electric arc furnace. In all cases, the goal is to oxidize some or all of the carbon, along with other impurities. On the other hand, other metals may be added to make alloy steel.
Annealing involves heating a piece of steel up to 700-800 Â ° C for several hours and then gradual cooling. It makes steel softer and more workable.
Apps
Metallurgical
Iron is the most widely used of all metals, accounting for more than 90% of metal production worldwide. Its low cost and high strength make it indispensable in engineering applications such as construction machinery and machine tools, automobiles, large hull boats, and structural components for buildings. Since pure iron is soft enough, it is most often combined with alloying elements to make steel.
? -Iron is a soft metal that can dissolve only small concentrations of carbon (not more than 0.021% of mass at 910 ° C). Austenite (? -iron) is both soft and metallic but can dissolve more carbon (as much as 2.04% of mass at 1146 ° C). This form of iron is used in a type of stainless steel used for making tableware, and hospital equipment and food-services.
Commercially available iron is classified based on purity and additives abundance. Pig iron has 3.5-4.5% carbon and contains various amount of contaminants such as sulfur, silicon and phosphorus. Rough iron is not a product that can be sold, but is a further step in the production of cast iron and steel. Reduced contaminants in pig iron that negatively impact material properties, such as sulfur and phosphorus, produce cast iron containing 2-4% carbon, silicon 1-6%, and a small amount of manganese. Pig iron has a melting point in the range 1420-1470 K, which is lower than either of the two main components, and makes it the first product to melt when carbon and iron are heated together. The mechanical properties vary greatly and depend on the shape carbon takes in the alloy.
Cast iron "White" contains their carbon in the form of cementite, or iron carbide (Fe 3 C). This harsh and brittle compound dominates the mechanical properties of the white cast iron, making it hard, but not resistant to shock. The damaged surface of the white cast iron is full of delicate aspects of faulty, pale iron-carbide, silver, glossy material, hence the name. Cooling the 0.8% carbon mixture slowly below 723 ° C to room temperature produces a separate layer, alternating cementite and '-some, soft and soft and is called a perlite for its appearance. Rapid cooling, on the other hand, does not allow time for this separation and creates a hard and brittle martensite. The steel can then be forged by reheating to the temperature in between, altering the proportions of pearlite and martensite. The final product under 0.8% carbon content is a pearlite-mixture, and that above 0.8% carbon content is a pearlite-melt mixture.
In carbon gray iron exists as separate, fine flakes of graphite, and also makes the material brittle due to the sharp flakes of graphite that produce the site of stress concentration in the material. The newer variant of gray iron, referred to as ductile iron is specifically treated with trace amounts of magnesium to convert the form of graphite to spheroids, or nodules, reduces the stress concentration and greatly increases the toughness and strength of the material.
Wrought iron contains less than 0.25% carbon but a large amount of slag gives fibrous characteristics. It is a hard and easily formed product, but not as smooth as pig iron. If sharpened to the edge, it loses quickly. Wrought iron is characterized by the presence of fine fibers of slag trapped within the metal. Wrought iron is more corrosion resistant than steel. Almost entirely replaced by mild steel for traditional "wrought iron" products and blacksmiths.
Lightweight steel corrosion is easier than wrought iron, but is cheaper and more widely available. Carbon steel contains 2.0% or less of carbon, with a small amount of manganese, sulfur, phosphorus, and silicon. Alloy steels contain various amounts of carbon as well as other metals, such as chromium, vanadium, molybdenum, nickel, tungsten, etc. The content of their alloys increases the cost, so it is usually only used for special use. One common alloy steel, is stainless steel. Recent developments in iron metallurgy have resulted in an increasingly growing series of steels, also called 'HSLA' or low-alloy low-alloy steels, which contain little additives to produce spectacular high strength and toughness at minimal cost.
In addition to traditional applications, iron is also used for protection from ionizing radiation. Though lighter than other traditional protection materials, lead, is much more mechanically powerful. The attenuation of radiation as an energy function is shown in the graph.
The main disadvantage of iron and steel is that pure iron, and most of its alloys, suffers from rust if it is not protected in some way, costing more than 1% of the world's economy. Painting, galvanizing, passivation, plastic coating and bluing are all used to protect iron from rust by removing water and oxygen or by cathodic protection. The rusting mechanism of iron is as follows:
- Cathode: 3 O 2 6 H 2 O 12 e - -> 12 OH -
- Anode: 4 Fe -> 4 Fe 2 8 e - ; 4 Fe 2 -> 4 Fe 3 4 e -
- Overall: 4 Fe 3 O 2 6 H 2 O -> 4 Fe 3 12 OH - -> 4 Fe (OH) 3 or 4 FeO (OH) 4 H 2 O
Electrolytes are usually iron (II) sulfates in urban areas (formed when atmospheric sulfur dioxide invades iron), and salt particles in the atmosphere in coastal areas.
Iron compound
Although the use of iron is dominant in metallurgy, iron compounds are also pervasive in the industry. Iron catalysts are traditionally used in the Haber-Bosch process for the production of ammonia and Fischer-Tropsch processes for the conversion of carbon monoxide into hydrocarbons for fuels and lubricants. Iron powder in an acid solvent is used in the reduction of Bechamp reduction of nitrobenzene to aniline.
Iron (III) chloride finds use in water purification and waste treatment, in cloth dyeing, as a dye in paint, as an additive in animal feed, and as an etchant for copper in the manufacture of printed circuit boards. It can also be dissolved in alcohol to form iron tincture, which is used as a medicine to stop bleeding in walnuts.
Iron (II) sulfate is used as a precursor for other iron compounds. It is also used to reduce chromate in cement. It is used to fortify food and treat iron deficiency anemia. Iron (III) sulfate is used in precipitating minute waste particles in the tank water. Iron (II) chloride is used as a reduction of flocculation agents, in the formation of iron complexes and magnetic iron oxides, and as reducing agents in organic synthesis.
Biological and pathological roles
Iron is required for life. The iron-sulfur group is pervasive and includes nitrogenase, the enzyme responsible for biological nitrogen fixation. The iron-containing protein participates in the transportation, storage and use of oxygen. Iron proteins are involved in the transfer of electrons.
Examples of iron-containing proteins in higher organisms include hemoglobin, cytochrome (see high-valent iron), and catalase. The average adult humans contain about 0.005% by weight of iron, or about four grams, of which three quarters are in hemoglobin - a level that remains constant even if only about one milligram of iron is absorbed daily, because the human body recycles its hemoglobin. for iron content.
Biochemistry
Iron acquisition poses a problem for aerobic organisms because ferrous iron does not dissolve well near neutral pH. Thus, these organisms have developed a way to absorb iron as a complex, sometimes taking iron iron before it oxidizes back to ferrous iron. In particular, bacteria have evolved very high sequestration agents called siderophores.
After the absorption of human cells, the storage of iron is precisely regulated. The main component of this regulation is protein transferrin, which binds iron ions absorbed from the duodenum and carries them in the blood to the cells. Transferrin contains Fe 3 in the center of the distorted octahedron, bound to one nitrogen, three oxygen and chelating carbonate anions that trap the Fe 3 ion: it has a high stability constant which is very effective at taking ion Fe 3 even from the most stable complex. In the bone marrow, transferrin is reduced from Fe 3 and Fe 2 and stored as ferritin to be incorporated into hemoglobin.
The most commonly known and studied bioinorganic iron compound (biological iron molecule) is heme protein: for example, hemoglobin, myoglobin, and cytochrome P450. These compounds participate in transporting gases, building enzymes, and transferring electrons. Metalloproteins are a group of proteins with metal ion cofactors. Some examples of iron metalloprotein are ferritin and rubredoxin. Many vital enzymes for life contain iron, such as catalase, lipoxygenase, and IRE-BP.
Hemoglobin is an oxygen carrier that occurs in red blood cells and donates their color, transporting oxygen in the arteries from the lungs to the muscles where it is transferred to myoglobin, which stores it until it is needed for the metabolic oxidation of glucose, generating energy.. Here hemoglobin binds carbon dioxide, produced when glucose is oxidized, which is transported through the vein by hemoglobin (mainly as an anion bicarbonate) back to the lungs where it is exhaled. In hemoglobin, iron is in one of four heme groups and has six possible coordination sites; four are occupied by a nitrogen atom in a porphyrin ring, the fifth by imidazole nitrogen in the histidine residue of one of the protein chains attached to the heme group, and the sixth are reserved for oxygen molecules which can be reversibly bound. When hemoglobin is not attached to oxygen (and then called deoxyhemoglobin), the Fe 2 ion in the middle of the heme group (in the interior of the hydrophobic proteins) is in a high rotation configuration. It is therefore too large to fit into a porphyrin ring, which curves into a dome with Fe > 2 ion about 55 pixometers above it. In this configuration, the sixth coordination site reserved for oxygen is blocked by other histidine residues.
When deoxyhemoglobin takes the oxygen molecule, this histidine residue moves away and returns once the oxygen is securely attached to form a hydrogen bond with it. This results in the Fe 2 ion switching to a low rotation configuration, resulting in a 20% reduction in ionic radius so that it can now enter into the porphyrin ring, which becomes planar. (In addition, this hydrogen bond produces a slope of the oxygen molecule, resulting in a Fe-OO bond angle of about 120 ° C which avoids the formation of Fe-O-Fe or Fe-O 2 - Fe bridge which will cause electron transfer , oxidation of Fe 2 to Fe 3 , and the destruction of hemoglobin.) This results in the movement of all proteins. a chain that leads to another subunit of hemoglobin to form changes with greater oxygen affinity. Thus, when deoxyhemoglobin takes oxygen, its affinity for more oxygen increases, and vice versa. Mioglobin, on the other hand, contains only one heme group and hence this cooperative effect can not occur. Thus, while hemoglobin is almost saturated with oxygen in high oxygen partial pressures found in the lungs, its affinity for oxygen is much lower than that of myoglobin, which is oxygenate even at the low partial pressure of oxygen found in muscle tissue. As explained by the Bohr effect (named after Christian Bohr, father of Niels Bohr), the oxygen affinity of hemoglobin is reduced in the presence of carbon dioxide.
Carbon monoxide and phosphorus trifluoride are toxic to humans because they bind to hemoglobin similar to oxygen, but with more strength, so that oxygen can no longer be transported throughout the body. Hemoglobin is bound to carbon monoxide known as carboxyhemoglobin. This effect also plays a small role in cyanide toxicity, but there have been major effects so far interfer- ence with the functioning of cytochrome electron transport proteins. The cytochrome protein also involves the heme group and is involved in the oxidation of metabolic glucose by oxygen. The location of the sixth coordination is then occupied by other imidazole nitrogen or methionine sulfur, so this protein is mostly inert to oxygen - with the exception of cytochrome a, which binds directly to oxygen and is thus very easily poisoned by cyanide. Here, electron transfer takes place as iron remains in low rotation but changes between 2 and 3 oxidation numbers. Because the reduction potential of each step is slightly larger than the previous one, energy is released step by step and thus can be stored in adenosine triphosphate. Cytochrome a little differently, as occurs in mitochondrial membranes, binds directly to oxygen, and transports protons and electrons, as follows:
- 4 Cytc 2 O 2 8H
inside -> 4 Cytc 3 2 H 2 O 4H < br> outside
Although heme protein is the most important class of iron-containing protein, iron-sulfur protein is also very important, involved in electron transfer, which may be because iron can be stable in both 2 or 3 oxidations. It has one, two, four, or eight iron atoms each of which is approximately tetrahedral coordinated to four sulfur atoms; because of this tetrahedral coordination, they always have high spin iron. The simplest compound is rubredoxin, which has only one iron atom that is coordinated to four sulfur atoms from cysteine ​​residues in the surrounding peptide chain. Another important class of iron sulfur protein is ferredoxins, which have several iron atoms. Transferrin does not belong to any of these classes.
The ability of sea shells to maintain their grip on rocks in the oceans is facilitated by their use of iron-based organometallic bonds in protein-rich cuticles. Based on a synthetic replica, the presence of iron in this structure increases the elastic modulus 770 times, tensile strength 58 times, and toughness 92 times. The amount of stress needed to permanently damage them increases 76 times.
Health and diet
Iron oozes, but especially rich sources of iron include red meat, oysters, nuts, nuts, poultry, fish,
Source of the article : Wikipedia
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