Iron is an element of a secondary subgroup of the eighth group of the fourth period of the periodic system of chemical elements with atomic number 26. It is designated by the symbol Fe (lat. Ferrum). One of the most common metals in the earth's crust (second place after aluminum).
The simple substance iron (CAS number: 7439-89-6) is a malleable silver-white metal with a high chemical reactivity: iron quickly corrodes at high temperatures or high humidity in air. In pure oxygen, iron burns, and in a finely dispersed state, it ignites spontaneously in air.
In fact, iron is usually called its alloys with a low content of impurities (up to 0.8%), which retain the softness and ductility of a pure metal. But in practice, alloys of iron with carbon are more often used: steel (up to 2.14 wt.% carbon) and cast iron (more than 2.14 wt.% carbon), as well as stainless (alloyed) steel with the addition of alloying metals (chromium, manganese, nickel, etc.). The combination of the specific properties of iron and its alloys make it "metal No. 1" in importance to humans.
In nature, iron is rarely found in its pure form, most often it occurs as part of iron-nickel meteorites. The prevalence of iron in the earth's crust is 4.65% (4th place after O, Si, Al). It is also believed that iron makes up most of the earth's core.
origin of name
There are several versions of the origin of the Slavic word "iron" (Belarusian zhalez, Ukrainian zalіzo, Old Slavic zhelѣzo, Bulgarian zhelyazo, Serbo-Chorvian zhelљzo, Polish żelazo, Czech železo, Slovenian železo).
One of the etymologies connects Praslav. *želězo with the Greek word χαλκός, which meant iron and copper, according to another version *želězo is related to the words *žely "tortoise" and *glazъ "rock", with the common seme "stone". The third version suggests an ancient borrowing from an unknown language.
The Romance languages (Italian ferro, French fer, Spanish hierro, Port ferro, Rum fier) continue lat. ferrum. Latin ferrum (Germanic languages borrowed the name of iron (Gothic eisarn, English iron, German Eisen, Dutch ijzer, Danish jern, Swedish järn) from Celtic.
The Pro-Celtic word *isarno- (> OE iarn, OE Bret. hoiarn) probably goes back to Proto-IE. *h1esh2r-no- "bloody" with semantic development "bloody" > "red" > "iron". According to another hypothesis, this word goes back to pra-i.e. *(H)ish2ro- "strong, holy, possessing supernatural power."
The ancient Greek word σίδηρος may have been borrowed from the same source as the Slavic, Germanic and Baltic words for silver.
The name of natural iron carbonate (siderite) comes from lat. sidereus - starry; indeed, the first iron that fell into the hands of people was of meteoric origin. Perhaps this coincidence is not accidental. In particular, the ancient Greek word sideros (σίδηρος) for iron and the Latin sidus meaning "star" are likely to have a common origin.
Receipt
In industry, iron is obtained from iron ore, mainly from hematite (Fe 2 O 3) and magnetite (FeO·Fe 2 O 3).
There are various ways to extract iron from ores. The most common is the domain process.
The first stage of production is the reduction of iron with carbon in a blast furnace at a temperature of 2000 °C. In a blast furnace, carbon in the form of coke, iron ore in the form of sinter or pellets, and flux (eg limestone) are fed from above and are met by a stream of forced hot air from below.
In the furnace, carbon in the form of coke is oxidized to carbon monoxide. This oxide is formed during combustion in the absence of oxygen. In turn, carbon monoxide recovers iron from the ore. To make this reaction go faster, heated carbon monoxide is passed through iron (III) oxide. Flux is added to get rid of undesirable impurities (primarily silicates; for example quartz) in the ore being mined. A typical flux contains limestone (calcium carbonate) and dolomite (magnesium carbonate). Other fluxes are used to eliminate other impurities.
The effect of the flux (in this case, calcium carbonate) is that when it is heated, it decomposes to its oxide. Calcium oxide combines with silicon dioxide, forming a slag - calcium metasilicate. Slag, unlike silicon dioxide, is melted in a furnace. Lighter than iron, slag floats on the surface - this property allows you to separate the slag from the metal. The slag can then be used in construction and agriculture. The molten iron obtained in a blast furnace contains quite a lot of carbon (cast iron). Except in such cases, when cast iron is used directly, it requires further processing.
Excess carbon and other impurities (sulphur, phosphorus) are removed from cast iron by oxidation in open-hearth furnaces or in converters. Electric furnaces are also used for smelting alloyed steels.
In addition to the blast furnace process, the process of direct production of iron is common. In this case, pre-crushed ore is mixed with special clay to form pellets. The pellets are roasted and treated in a shaft furnace with hot methane conversion products that contain hydrogen. Hydrogen easily reduces iron without contaminating iron with impurities such as sulfur and phosphorus, which are common impurities in coal. Iron is obtained in solid form, and then melted down in electric furnaces.
Chemically pure iron is obtained by electrolysis of solutions of its salts.
is a component of hemoglobin. This complex protein is found in red blood cells, also known as red blood cells. Without them, in fact, the blood would not be scarlet, and there would be no life.
Red blood cells transport carbon dioxide and oxygen throughout the body. They are essential for life. What else is needed iron, what are its properties and cost in the literal and figurative sense?
Chemical and physical properties of iron
Touched iron in a cool room? The cold from touching the metal is the result of its high thermal conductivity. The material instantly takes the energy of the body, transferring it to the environment. As a result, the person becomes cold.
Electrical conductivity of iron also top notch. The metal easily transmits current due to the free electrons in the atom. It has 7 layers. The last 2 have 8 electrons. When excited, they can all be valence, that is, capable of forming new bonds.
Externally metal iron silver grey. There are native forms. pure iron plastic and malleable. It has a pronounced metallic luster and an average hardness of 4 points. 10 points is an indicator of the hardest stone on earth - diamond, and talc is marked with 1 point.
Iron is an element medium toughness. The metal boils at 2860 degrees, and softens at 1539. In this state, the material loses its ferromagnetic properties. They are inherent only in the solid state of iron. The element becomes a magnet when it enters the field.
But, more interesting is that after its disappearance, the metal remains a magnet for a long time. This feature is due to the same free electrons in the structure of the atom. Moving, the particles change its structure and properties.
Iron is a chemical element, easily reacting with bromine, fluorine, chlorine and other halogens. These are the elements of the 17th group of the periodic table. Under normal conditions, interaction with oxygen also proceeds.
Now, about the heating reactions. When a metal is burned, its oxides are formed. There are several types of them: - 2FeO, 2Fe 2 O 3, Fe 3 O 4. Which one will turn out depends on the proportions of the original elements and the conditions of combination. The properties of oxides vary.
Heating starts and reacts with . It needs 6 moles of iron and one mole of gas. Yield - 2 moles of nitride of the 26th element. Its phosphide is already formed in combination with phosphorus. Another simple substance that combines with ferrum is. It turns out, of course, sulfide. An addition reaction takes place.
Of complex substances, that is, consisting of molecules, iron interacts with acids. Metal displaces hydrogen from them. It turns out a replacement. So, and interaction with sulfuric acid leaves ferrum sulfate and pure hydrogen.
Reactions with are also possible. Their iron restores. In other words, the 26th element releases a less active metal from substances. By combining ferrum, for example, with copper sulfate, iron sulfate is obtained. remains in its original form.
The use of iron
Where is the iron applied, follows from its properties. Ferromagnetism is useful in the manufacture of souvenirs and industrial installations. In other words, magnets are made of metal, both for refrigerators and for large industries. The strength of the material, hardness - a reason to use it for the manufacture of weapons and armor.
Models from meteoric iron. In cosmic bodies, the properties of ferrum are enhanced. Therefore, knives and armor are especially sharp and durable. Signs of iron meteorite was noticed in ancient Rome.
Known and iron alloys in particular cast iron and steel. Things of a household, everyday nature are cast from them, for example, fences, gazebos, accessories. Ferrum is also used for industrial purposes. Interestingly, the composition of steel and cast iron is the same, the proportions are different. And there, and there merge iron with carbon. In steel, gas is less than 1.7%. In cast iron, carbon is from 1.7 to 4.5%.
Carbon in iron alloys plays the role of a strengthening element. It reduces the susceptibility of the mixture to corrosion and makes the material heat resistant. Other additives are also added to steels. No wonder there are different brands of alloy. With, for example, they produce impact-resistant and, at the same time, ductile steel.
In the form of chloride, the 26th element is used to purify water. Metal is also useful in medicine. iron treatment necessary for anemia. This is a lack of red blood cells and the metal in their composition. Iron preparations they are also prescribed to patients with tuberculosis, sciatica, suffering from convulsions and bleeding from the nose.
The 26th element is also necessary for the normal functioning of the thyroid gland. Usually, its dysfunction is associated with deficiency. However, he is not alone in ensuring the health of the gland.
A lot of ferrum and in the cells of the liver. There, the metal helps to neutralize harmful substances, toxins. To maintain the human body must receive at least 20 milligrams of iron per day.
Iron mining
Iron is a common metal. There are many minerals in nature, which are based on the 26th element. Most ferrum in and. Of them, and remove iron.
The metal reduction reaction is carried out. For this, coke is needed, that is, a compound of carbon. The interaction takes place at a temperature of 2000 degrees Celsius, in domain.
Blast furnaces are dispensed with when restoring ferrum with pure hydrogen. Shaft furnaces are already required. So called models elongated vertically.
The working space of the apparatus is similar to a cylinder or a cone. They put crushed iron ore, mixed with special . Then, hydrogen is added. The result is the same - pure ferrum.
iron price
The cost of metal depends on the type of product. Most things are made from ferrum alloys, such as roofing materials. Roof coverings are usually sheet. The price per square meter varies from 300 to more than 600 rubles, depending on the thickness of the iron.
Roofing sheets are corrugated, of complex geometry and special composition. Simple layers are cheaper. There are offers to buy 30 sheets 2.5 by 1.3 meters for 1000 rubles. Thickness - 1.5 mm.
A pure element in tablets costs about 1600 rubles for 180-200 pieces. If a finished product is purchased, in which manual labor is invested, it can be difficult to keep within tens, hundreds of thousands. A striking example is forged products for individual orders.
For unusual gates, furniture, vases, blacksmiths "break" a considerable sum. Most of the price is not the material, but human labor, the realization of the idea.
As for the cost of iron-bearing ore, about 40 US dollars are asked for in Russia per ton. This is the price tag for raw materials with 60 percent ferrum content. When a pure powder of the 26th element is isolated, for 1000 kilograms they ask for no less than 560-600 US dollars.
Most firms sell wholesale. Offers to buy just one kilo of metal are rare. 1000 grams costs about 1-1.5 dollars. Some companies pack ferrum powder in bags of 5, 10, 25 kilograms. Sale ads posted on the Internet.
Iron is a well-known chemical element. It belongs to the metals with average reactivity. We will consider the properties and use of iron in this article.
Prevalence in nature
There is a fairly large number of minerals that include ferrum. First of all, it is magnetite. It is seventy-two percent iron. Its chemical formula is Fe 3 O 4 . This mineral is also called magnetic iron ore. It has a light gray color, sometimes with dark gray, up to black, with a metallic sheen. Its largest deposit among the CIS countries is located in the Urals.
The next mineral with a high iron content is hematite - it consists of seventy percent of this element. Its chemical formula is Fe 2 O 3 . It is also called red iron ore. It has a color from red-brown to red-gray. The largest deposit in the territory of the CIS countries is located in Krivoy Rog.
The third mineral in terms of ferrum content is limonite. Here, iron is sixty percent of the total mass. It is a crystalline hydrate, that is, water molecules are woven into its crystal lattice, its chemical formula is Fe 2 O 3 .H 2 O. As the name implies, this mineral has a yellow-brownish color, occasionally brown. It is one of the main components of natural ocher and is used as a pigment. It is also called brown ironstone. The largest occurrences are the Crimea, the Urals.
In siderite, the so-called spar iron ore, forty-eight percent of ferrum. Its chemical formula is FeCO 3 . Its structure is heterogeneous and consists of crystals of different colors connected together: gray, pale green, gray-yellow, brown-yellow, etc.
The last naturally occurring mineral with a high ferrum content is pyrite. It has the following chemical formula FeS 2 . Iron in it is forty-six percent of the total mass. Due to the sulfur atoms, this mineral has a golden yellow color.
Many of the minerals considered are used to obtain pure iron. In addition, hematite is used in the manufacture of jewelry from natural stones. Pyrite inclusions can be found in lapis lazuli jewelry. In addition, iron is found in nature in the composition of living organisms - it is one of the most important components of the cell. This trace element must be supplied to the human body in sufficient quantities. The healing properties of iron are largely due to the fact that this chemical element is the basis of hemoglobin. Therefore, the use of ferrum has a good effect on the state of the blood, and therefore the whole organism as a whole.
Iron: physical and chemical properties
Let's take a look at these two major sections in order. iron is its appearance, density, melting point, etc. That is, all the distinctive features of a substance that are associated with physics. The chemical properties of iron are its ability to react with other compounds. Let's start with the first.
Physical properties of iron
In its pure form under normal conditions, it is a solid. It has a silvery-gray color and a pronounced metallic sheen. The mechanical properties of iron include a hardness level of She equals four (medium). Iron has good electrical and thermal conductivity. The last feature can be felt by touching an iron object in a cold room. Since this material conducts heat quickly, it takes a lot of it out of your skin in a short amount of time, which is why you feel cold.
Touching, for example, a tree, it can be noted that its thermal conductivity is much lower. The physical properties of iron are its melting and boiling points. The first is 1539 degrees Celsius, the second is 2860 degrees Celsius. It can be concluded that the characteristic properties of iron are good ductility and fusibility. But that's not all.
The physical properties of iron also include its ferromagnetism. What it is? Iron, whose magnetic properties we can observe in practical examples every day, is the only metal that has such a unique distinguishing feature. This is due to the fact that this material is able to be magnetized under the influence of a magnetic field. And after the termination of the action of the latter, iron, the magnetic properties of which have just been formed, remains a magnet for a long time. This phenomenon can be explained by the fact that in the structure of this metal there are many free electrons that are able to move.
In terms of chemistry
This element belongs to the metals of medium activity. But the chemical properties of iron are typical for all other metals (except those that are to the right of hydrogen in the electrochemical series). It is capable of reacting with many classes of substances.
Let's start simple
Ferrum interacts with oxygen, nitrogen, halogens (iodine, bromine, chlorine, fluorine), phosphorus, carbon. The first thing to consider is reactions with oxygen. When ferrum is burned, its oxides are formed. Depending on the conditions of the reaction and the proportions between the two participants, they can be varied. As an example of such interactions, the following reaction equations can be given: 2Fe + O 2 = 2FeO; 4Fe + 3O 2 \u003d 2Fe 2 O 3; 3Fe + 2O 2 \u003d Fe 3 O 4. And the properties of iron oxide (both physical and chemical) can be varied, depending on its variety. These reactions take place at high temperatures.
The next is the interaction with nitrogen. It can also occur only under the condition of heating. If we take six moles of iron and one mole of nitrogen, we get two moles of iron nitride. The reaction equation will look like this: 6Fe + N 2 = 2Fe 3 N.
When interacting with phosphorus, a phosphide is formed. To carry out the reaction, the following components are necessary: for three moles of ferrum - one mole of phosphorus, as a result, one mole of phosphide is formed. The equation can be written as follows: 3Fe + P = Fe 3 P.
In addition, among reactions with simple substances, interaction with sulfur can also be distinguished. In this case, sulfide can be obtained. The principle by which the process of formation of this substance occurs is similar to those described above. Namely, an addition reaction occurs. All chemical interactions of this kind require special conditions, mainly high temperatures, less often catalysts.
Also common in the chemical industry are reactions between iron and halogens. These are chlorination, bromination, iodination, fluorination. As is clear from the names of the reactions themselves, this is the process of adding chlorine / bromine / iodine / fluorine atoms to ferrum atoms to form chloride / bromide / iodide / fluoride, respectively. These substances are widely used in various industries. In addition, ferrum is able to combine with silicon at high temperatures. Due to the fact that the chemical properties of iron are diverse, it is often used in the chemical industry.
Ferrum and complex substances
From simple substances, let's move on to those whose molecules consist of two or more different chemical elements. The first thing to mention is the reaction of ferrum with water. Here are the main properties of iron. When water is heated, it forms together with iron (it is called so because, when interacting with the same water, it forms a hydroxide, in other words, a base). So, if you take one mole of both components, substances such as ferrum dioxide and hydrogen are formed in the form of a gas with a pungent odor - also in molar proportions of one to one. The equation for this kind of reaction can be written as follows: Fe + H 2 O \u003d FeO + H 2. Depending on the proportions in which these two components are mixed, iron di- or trioxide can be obtained. Both of these substances are very common in the chemical industry and are also used in many other industries.
With acids and salts
Since ferrum is located to the left of hydrogen in the electrochemical series of metal activity, it is able to displace this element from compounds. An example of this is the substitution reaction that can be observed when iron is added to an acid. For example, if you mix iron and sulphate acid (aka sulfuric acid) of medium concentration in the same molar proportions, the result will be ferrous sulfate (II) and hydrogen in the same molar proportions. The equation for such a reaction will look like this: Fe + H 2 SO 4 \u003d FeSO 4 + H 2.
When interacting with salts, the reducing properties of iron are manifested. That is, with the help of it, a less active metal can be isolated from salt. For example, if you take one mole and the same amount of ferrum, then you can get iron sulfate (II) and pure copper in the same molar proportions.
Significance for the body
One of the most common chemical elements in the earth's crust is iron. we have already considered, now we will approach it from a biological point of view. Ferrum performs very important functions both at the cellular level and at the level of the whole organism. First of all, iron is the basis of such a protein as hemoglobin. It is necessary for the transport of oxygen through the blood from the lungs to all tissues, organs, to every cell of the body, primarily to the neurons of the brain. Therefore, the beneficial properties of iron cannot be overestimated.
In addition to the fact that it affects blood formation, ferrum is also important for the full functioning of the thyroid gland (this requires not only iodine, as some believe). Iron also takes part in intracellular metabolism, regulates immunity. Ferrum is also found in especially large quantities in liver cells, as it helps to neutralize harmful substances. It is also one of the main components of many types of enzymes in our body. The daily diet of a person should contain from ten to twenty milligrams of this trace element.
Foods rich in iron
There are many. They are of both plant and animal origin. The first are cereals, legumes, cereals (especially buckwheat), apples, mushrooms (white), dried fruits, rose hips, pears, peaches, avocados, pumpkin, almonds, dates, tomatoes, broccoli, cabbage, blueberries, blackberries, celery, etc. The second - liver, meat. The use of foods high in iron is especially important during pregnancy, as the body of the developing fetus requires a large amount of this trace element for proper growth and development.
Signs of iron deficiency in the body
Symptoms of too little ferrum entering the body are fatigue, constant freezing of the hands and feet, depression, brittle hair and nails, decreased intellectual activity, digestive disorders, low performance, and thyroid disorders. If you notice more than one of these symptoms, you may want to increase the amount of iron-rich foods in your diet or buy vitamins or supplements containing ferrum. Also, be sure to consult a doctor if any of these symptoms you feel too acute.
The use of ferrum in industry
The uses and properties of iron are closely related. Due to its ferromagnetism, it is used to make magnets - both weaker for domestic purposes (souvenir fridge magnets, etc.), and stronger - for industrial purposes. Due to the fact that the metal in question has high strength and hardness, it has been used since ancient times for the manufacture of weapons, armor and other military and household tools. By the way, even in ancient Egypt meteorite iron was known, the properties of which are superior to those of ordinary metal. Also, such a special iron was used in ancient Rome. They made elite weapons from it. Only a very rich and noble person could have a shield or sword made of meteorite metal.
In general, the metal that we are considering in this article is the most versatile among all the substances in this group. First of all, steel and cast iron are made from it, which are used for the production of all kinds of products necessary both in industry and in everyday life.
Cast iron is an alloy of iron and carbon, in which the second is present from 1.7 to 4.5 percent. If the second is less than 1.7 percent, then this kind of alloy is called steel. If about 0.02 percent of carbon is present in the composition, then this is already ordinary technical iron. The presence of carbon in the alloy is necessary to give it greater strength, thermal stability, and rust resistance.
In addition, steel can contain many other chemical elements as impurities. This is manganese, and phosphorus, and silicon. Also, chromium, nickel, molybdenum, tungsten and many other chemical elements can be added to this kind of alloy to give it certain qualities. Types of steel in which a large amount of silicon is present (about four percent) are used as transformer steels. Those containing a lot of manganese (up to twelve to fourteen percent) find their use in the manufacture of parts for railways, mills, crushers and other tools, parts of which are subject to rapid abrasion.
Molybdenum is introduced into the composition of the alloy to make it more thermally stable - such steels are used as tool steels. In addition, to obtain well-known and commonly used stainless steels in the form of knives and other household tools, it is necessary to add chromium, nickel and titanium to the alloy. And in order to get shock-resistant, high-strength, ductile steel, it is enough to add vanadium to it. When introduced into the composition of niobium, it is possible to achieve high resistance to corrosion and the effects of chemically aggressive substances.
The mineral magnetite, which was mentioned at the beginning of the article, is needed for the manufacture of hard drives, memory cards and other devices of this type. Due to its magnetic properties, iron can be found in the construction of transformers, motors, electronic products, etc. In addition, ferrum can be added to other metal alloys to give them greater strength and mechanical stability. The sulfate of this element is used in horticulture for pest control (along with copper sulfate).
They are indispensable in water purification. In addition, magnetite powder is used in black and white printers. The main use of pyrite is to obtain sulfuric acid from it. This process occurs in the laboratory in three stages. In the first stage, ferrum pyrite is burned to produce iron oxide and sulfur dioxide. At the second stage, the conversion of sulfur dioxide into its trioxide occurs with the participation of oxygen. And at the final stage, the resulting substance is passed through in the presence of catalysts, thereby obtaining sulfuric acid.
Getting iron
This metal is mainly mined from its two main minerals: magnetite and hematite. This is done by reducing iron from its compounds with carbon in the form of coke. This is done in blast furnaces, the temperature in which reaches two thousand degrees Celsius. In addition, there is a way to reduce the ferrum with hydrogen. This does not require a blast furnace. To implement this method, special clay is taken, mixed with crushed ore and treated with hydrogen in a shaft furnace.
Conclusion
The properties and uses of iron are varied. This is perhaps the most important metal in our lives. Having become known to mankind, he took the place of bronze, which at that time was the main material for the manufacture of all tools, as well as weapons. Steel and cast iron are in many ways superior to the alloy of copper and tin in terms of their physical properties, resistance to mechanical stress.
In addition, iron is more common on our planet than many other metals. it in the earth's crust is almost five percent. It is the fourth most abundant chemical element in nature. Also, this chemical element is very important for the normal functioning of the organism of animals and plants, primarily because hemoglobin is built on its basis. Iron is an essential trace element, the use of which is important for maintaining health and normal functioning of organs. In addition to the above, it is the only metal that has unique magnetic properties. Without ferrum it is impossible to imagine our life.
Iron
IRON-a; cf.
1. A chemical element (Fe), a malleable, silvery metal that combines with carbon to form steel and cast iron.
2. The common name for mild steel, a silver-colored metal. Forge The wind rattles the iron of the roof.
3. About what is strong, solid, strong (about external physical qualities). You have your hands! // About what is tough, inflexible (about internal moral qualities). His character is.
4. Razg. Of a remedy containing glandular substances. The body lacks iron. Drink well. Apples contain
5. Razg. tech. Computer hardware (as opposed to software). Buy the missing iron.
◊ Burn with hot iron. To eradicate, destroy smth., resorting to extreme, extraordinary measures. Strike while the iron is hot (see Forge).
◁ Iron; Glandular; piece of iron; Iron (see).
iron(lat. Ferrum), a chemical element of group VIII of the periodic system. Shiny silvery white metal. Forms polymorphic modifications; at ordinary temperature, α-Fe is stable (crystal lattice - cubic body-centered) with a density of 7.874 g / cm 3. α-Fe up to 769°C (Curie point) ferromagnetic; t pl 1535°C. Oxidizes in air - covered with loose rust. According to the prevalence of elements in nature, iron is in 4th place; forms about 300 minerals. Iron alloys with carbon and other elements account for about 95% of all metal products (cast iron, steel, ferroalloys). In its pure form, it is practically not used (in everyday life, steel or cast iron products are often called iron). Necessary for the life of animal organisms; is part of hemoglobin.
IRONIRON (lat. Ferrum), Fe (read "ferrum"), chemical element, atomic number 26, atomic mass 55.847. The origin of both the Latin and Russian names of the element has not been unambiguously established. Natural iron is a mixture of four nuclides (cm. NUCLIDE) with mass numbers 54 (content in the natural mixture 5.82% by mass), 56 (91.66%), 57 (2.19%) and 58 (0.33%). Configuration of two outer electron layers 3 s 2
p 6
d 6
4s 2
. Usually forms compounds in oxidation states +3 (valency III) and +2 (valency II). There are also known compounds with iron atoms in the oxidation states +4, +6 and some others.
In the periodic system of Mendeleev, iron is included in group VIIIB. In the fourth period, to which iron belongs, this group also includes cobalt. (cm. COBALT) and nickel (cm. NICKEL). These three elements form a triad and have similar properties.
The radius of the neutral iron atom is 0.126 nm, the radius of the Fe 2+ ion is 0.080 nm, and the Fe 3+ ion is 0.067 nm. The energies of successive ionization of the iron atom are 7.893, 16.18, 30.65, 57, 79 eV. Electron affinity 0.58 eV. On the Pauling scale, the electronegativity of iron is about 1.8.
High purity iron is a lustrous, silvery-grey, ductile metal that lends itself well to various machining methods.
Being in nature
In the earth's crust, iron is widely distributed - it accounts for about 4.1% of the mass of the earth's crust (4th place among all elements, 2nd among metals). A large number of ores and minerals containing iron are known. Red iron ore (ore hematite (cm. HEMATITE), Fe 2 O 3 ; contains up to 70% Fe), magnetic iron ore (magnetite ore (cm. MAGNETITE), Fe 3 O 4; contains 72.4% Fe), brown iron ore (ore hydrogoethite HFeO 2 n H 2 O), as well as spar iron ore (siderite ore (cm. SIDERITE), iron carbonate, FeСО 3 ; contains about 48% Fe). There are also large deposits of pyrite in nature. (cm. PYRITE) FeS 2 (other names are sulfur pyrites, iron pyrites, iron disulfide and others), but ores with a high sulfur content are not yet of practical importance. In terms of iron ore reserves, Russia ranks first in the world. In sea water 1 10 -5 -1 10 -8% iron.
History of iron production
Iron has played and is playing an exceptional role in the material history of mankind. The first metallic iron that fell into the hands of man was probably of meteoric origin. Iron ores are widespread and often found even on the surface of the Earth, but native iron on the surface is extremely rare. Probably, a few thousand years ago, a person noticed that after burning a fire, in some cases, the formation of iron is observed from those pieces of ore that accidentally ended up in a fire. When burning a fire, the reduction of iron from the ore occurs due to the reaction of the ore both directly with coal and with carbon monoxide (II) CO formed during combustion. The possibility of obtaining iron from ores greatly facilitated the discovery of the fact that when the ore is heated with coal, a metal is formed, which can then be further refined during forging. Obtaining iron from ore using a cheese-making process was invented in Western Asia in the 2nd millennium BC. e. Period from the 9th to the 7th c. BC e., when iron metallurgy developed among many tribes of Europe and Asia, it was called the Iron Age, (cm. IRON AGE) succeeding the Bronze Age (cm. BRONZE AGE). Improvement in blowing methods (furs replaced natural draft) and an increase in the height of the hearth (low-shaft furnaces appeared) led to the production of cast iron, which began to be widely smelted in Western Europe from the 14th century. The resulting cast iron was converted into steel. Since the middle of the 18th century, coal-coke began to be used in the blast-furnace process instead of charcoal. (cm. COKE). In the future, methods for producing iron from ores were significantly improved, and at present special devices are used for this - blast furnaces, oxygen converters, electric arc furnaces.
Physical and chemical properties
At temperatures from room temperature to 917 °C, as well as in the temperature range 1394-1535 °C, a-Fe exists with a cubic body-centered lattice; at room temperature, the lattice parameter a = 0.286645 nm. At temperatures of 917-1394 ° C, b-Fe is stable with a cubic face-centered lattice T (a = 0.36468 nm). At temperatures from room temperature to 769 °C (the so-called Curie point (cm. CURIE POINT)) iron has strong magnetic properties (it is said to be ferromagnetic), at higher temperatures iron behaves like a paramagnet. Sometimes paramagnetic a-Fe with a cubic body-centered lattice, stable at temperatures from 769 to 917 ° C, is considered as the g-modification of iron, and b-Fe, stable at high temperatures (1394-1535 ° C), is traditionally called d- Fe (the idea of the existence of four modifications of iron - a, b, g and d- arose when there was no X-ray diffraction analysis and there was no objective information about the internal structure of iron). Melting point 1535 ° C, boiling point 2750 ° C, density 7.87 g / cm 3. The standard potential of the Fe 2+ /Fe 0 pair is -0.447V, the Fe 3+ /Fe 2+ pair is +0.771V.
When stored in air at temperatures up to 200 °C, iron is gradually covered with a dense film of oxide, which prevents further oxidation of the metal. In humid air, iron is covered with a loose layer of rust, which does not prevent the access of oxygen and moisture to the metal and its destruction. Rust does not have a constant chemical composition; approximately its chemical formula can be written as Fe 2 O 3 xH 2 O.
Iron reacts with oxygen when heated. When iron is burned in air, Fe 2 O 3 oxide is formed; when burned in pure oxygen, Fe 3 O 4 oxide is formed. When oxygen or air is passed through molten iron, FeO oxide is formed. When sulfur and iron powder are heated, sulfide is formed, the approximate formula of which can be written as FeS.
Iron reacts with halogens when heated (cm. HALOGENS). Since FeF 3 is non-volatile, iron is resistant to fluorine up to a temperature of 200-300°C. When iron is chlorinated (at a temperature of about 200°C), volatile FeCl 3 is formed. If the interaction of iron and bromine proceeds at room temperature or with heating and elevated bromine vapor pressure, then FeBr 3 is formed. When heated, FeCl 3 and, especially, FeBr 3 split off the halogen and turn into iron (II) halides. When iron and iodine interact, Fe 3 I 8 iodide is formed.
When heated, iron reacts with nitrogen, forming iron nitride Fe 3 N, with phosphorus, forming phosphides FeP, Fe 2 P and Fe 3 P, with carbon, forming Fe 3 C carbide, with silicon, forming several silicides, for example, FeSi.
At elevated pressure, metallic iron reacts with carbon monoxide CO, and liquid, under normal conditions, easily volatile iron pentacarbonyl Fe (CO) 5 is formed. Iron carbonyls of compositions Fe 2 (CO) 9 and Fe 3 (CO) 12 are also known. Iron carbonyls serve as starting materials in the synthesis of organo-iron compounds, including ferrocene (cm. FERROCENE) composition.
Pure metallic iron is stable in water and in dilute alkali solutions. In concentrated sulfuric and nitric acids, iron does not dissolve, since a strong oxide film passivates its surface.
With hydrochloric and dilute (approximately 20%) sulfuric acids, iron reacts to form iron (II) salts:
Fe + 2HCl \u003d FeCl 2 + H 2
Fe + H 2 SO 4 \u003d FeSO 4 + H 2
When iron interacts with approximately 70% sulfuric acid, the reaction proceeds with the formation of iron (III) sulfate:
2Fe + 4H 2 SO 4 \u003d Fe 2 (SO 4) 3 + SO 2 + 4H 2 O
Iron oxide (II) FeO has basic properties, it corresponds to the base Fe (OH) 2. Iron oxide (III) Fe 2 O 3 is weakly amphoteric, it corresponds to an even weaker than Fe (OH) 2 base Fe (OH) 3, which reacts with acids:
2Fe(OH) 3 + 3H 2 SO 4 = Fe 2 (SO 4) 3 + 6H 2 O
Iron hydroxide (III) Fe(OH) 3 exhibits weakly amphoteric properties; it is able to react only with concentrated alkali solutions:
Fe (OH) 3 + KOH \u003d K
The hydroxocomplexes of iron (III) thus formed are stable in strongly alkaline solutions. When solutions are diluted with water, they are destroyed, and iron (III) Fe (OH) 3 hydroxide precipitates.
Iron (III) compounds in solutions are reduced by metallic iron:
Fe + 2FeCl 3 \u003d 3FeCl 2
When storing aqueous solutions of iron (II) salts, oxidation of iron (II) to iron (III) is observed:
4FeCl 2 + O 2 + 2H 2 O \u003d 4Fe (OH) Cl 2
Of the salts of iron (II) in aqueous solutions, Mohr's salt is stable - double ammonium sulfate and iron (II) (NH 4) 2 Fe (SO 4) 2 6H 2 O.
Iron (III) is able to form double sulfates with singly charged alum-type cations, for example, KFe (SO 4) 2 - potassium iron alum, (NH 4) Fe (SO 4) 2 - iron ammonium alum, etc.
Under the action of gaseous chlorine or ozone on alkaline solutions of iron (III) compounds, iron (VI) compounds are formed - ferrates, for example, potassium ferrate (VI) K 2 FeO 4. There are reports of the production of iron (VIII) compounds under the action of strong oxidizing agents.
To detect iron (III) compounds in solution, a qualitative reaction of Fe 3+ ions with thiocyanate ions CNS - is used. When Fe 3+ ions interact with CNS - anions, bright red iron thiocyanate Fe(CNS) 3 is formed. Another reagent for Fe 3+ ions is potassium hexacyanoferrate (II) K 4 (previously this substance was called yellow blood salt). When the Fe 3+ and 4- ions interact, a bright blue precipitate precipitates.
A solution of potassium hexacyanoferrate (III) K 3, previously called red blood salt, can serve as a reagent for Fe 2+ ions in solution. During the interaction of Fe 3+ and 3- ions, a bright blue precipitate of the same composition precipitates as in the case of the interaction of Fe 3+ and 4- ions.
Alloys of iron with carbon
Iron is used mainly in alloys, primarily in alloys with carbon - various cast irons and steels. In cast iron, the carbon content is higher than 2.14% by mass (usually at the level of 3.5-4%), in steels the carbon content is lower (usually at the level of 0.8-1%).
Cast iron is obtained in blast furnaces. The blast furnace is a giant (up to 30-40 m high) truncated cone, hollow inside. The walls of the blast furnace are lined with refractory bricks from the inside, the thickness of the masonry is several meters. From above, enriched (freed from waste rock) iron ore, coke reducing agent (special grades of hard coal subjected to coking - heated at a temperature of about 1000 ° C without air), as well as melting materials (limestone and others) that contribute to the separation from smelted metal impurities - slag. From below, blast (pure oxygen or oxygen-enriched air) is fed into the blast furnace. As the materials loaded into the blast furnace descend, their temperature rises to 1200-1300 °C. As a result of reduction reactions occurring mainly with the participation of coke C and CO:
Fe 2 O 3 + 3C \u003d 2Fe + 3CO;
Fe 2 O 3 + 3CO = 2Fe + 3CO 2
metallic iron is formed, which is saturated with carbon and flows down.
This melt is periodically discharged from the blast furnace through a special hole - a tap-hole - and the melt is allowed to solidify in special forms. Cast iron is white, the so-called pig iron (it is used to produce steel) and gray, or cast iron. White cast iron is a solid solution of carbon in iron. Graphite microcrystals can be distinguished in the microstructure of gray cast iron. Due to the presence of graphite, gray cast iron leaves a mark on white paper.
Cast iron is brittle, it pricks upon impact, so springs, springs, and any products that must work in bending cannot be made from it.
Solid cast iron is lighter than molten cast iron, so that when it solidifies, it does not contract (as is usual with the solidification of metals and alloys), but expand. This feature allows you to make various castings from cast iron, including using it as a material for artistic casting.
If the carbon content in cast iron is reduced to 1.0-1.5%, then steel is formed. Steels are carbon (in such steels there are no other components except Fe and C) and alloyed (such steels contain additives of chromium, nickel, molybdenum, cobalt and other metals that improve the mechanical and other properties of steel).
Steel is obtained by processing pig iron and scrap metal in an oxygen converter, in an electric arc or open-hearth furnace. With such processing, the carbon content in the alloy is reduced to the required level, as they say, excess carbon burns out.
The physical properties of steel differ significantly from the properties of cast iron: steel is elastic, it can be forged, rolled. Since steel, unlike cast iron, contracts during solidification, the resulting steel castings are subjected to compression in rolling mills. After rolling, voids and shells disappear in the volume of the metal, which appeared during the solidification of the melts.
Steel production in Russia has long deep traditions, and the steels obtained by our metallurgists are of high quality.
The use of iron, its alloys and compounds
Pure iron has rather limited uses. It is used in the manufacture of electromagnet cores, as a catalyst for chemical processes, and for some other purposes. But iron alloys - cast iron and steel - form the basis of modern technology. Many iron compounds are also widely used. So, iron (III) sulfate is used in water treatment, iron oxides and cyanide serve as pigments in the manufacture of dyes, and so on.
iron in the body
Iron is present in all plants and animals as a trace element. (cm. MICROELEMENTS) that is, in very small quantities (about 0.02% on average). However, iron bacteria (cm. IRON BACTERIA), using the energy of oxidation of iron (II) to iron (III) for chemosynthesis (cm. CHEMOSYNTHESIS), can accumulate up to 17-20% iron in their cells. The main biological function of iron is participation in oxygen transport and oxidative processes. Iron performs this function as part of complex proteins - hemoproteins. (cm. HEMOPROTEIDS), whose prosthetic group is the iron porphyrin complex - heme (cm. GEM). Among the most important hemoproteins, respiratory pigments are hemoglobin. (cm. HEMOGLOBIN) and myoglobin (cm. MYOGLOBIN) universal electron carriers in the reactions of cellular respiration, oxidation and cytochrome photosynthesis, (cm. CYTOCHROMES) catalose and peroxide enzymes, and others. In some invertebrates, the iron-containing respiratory pigments heloerythrin and chlorocruorin have a different structure from hemoglobins. During the biosynthesis of hemoproteins, iron passes to them from the protein ferritin (cm. FERRITIN) that stores and transports iron. This protein, one molecule of which includes about 4,500 iron atoms, is concentrated in the liver, spleen, bone marrow, and intestinal mucosa of mammals and humans. The daily human need for iron (6-20 mg) is covered in excess by food (meat, liver, eggs, bread, spinach, beets and others are rich in iron). The body of an average person (body weight 70 kg) contains 4.2 g of iron, 1 liter of blood contains about 450 mg. With a lack of iron in the body, glandular anemia develops, which is treated with drugs containing iron. Iron preparations are also used as general tonic. An excess dose of iron (200 mg or more) can be toxic. Iron is also necessary for the normal development of plants, so there are microfertilizers based on iron preparations.
encyclopedic Dictionary. 2009 .
Synonyms:See what "iron" is in other dictionaries:
Wed hall (s) zo south., west. metal, crusher, smelted from ore in the form of cast iron, and forged from this latter under a blooming hammer. When combined with carbon, it forms steel. Iron goes on sale in the form of: strip or high-quality; first straight... Dahl's Explanatory Dictionary
17. d - elements. Iron, general characteristics, properties. Oxides and hydroxides, CO and OM characteristics, biorole, ability to complex formation.
1. General characteristics.
Iron - d-element of the secondary subgroup of the eighth group of the fourth period of PSCE with atomic number 26.
One of the most common metals in the earth's crust (second place after aluminum).
A simple substance iron is a malleable silver-white metal with a high chemical reactivity: iron quickly corrodes at high temperatures or high humidity in the air.
4Fe + 3O2 + 6H2O = 4Fe(OH)3
In pure oxygen, iron burns, and in a finely dispersed state, it ignites spontaneously in air.
3Fe + 2O2 = FeO + Fe2O3
3Fe + 4H2O = FeO*Fe2O3
FeO*Fe2O3 = Fe3O4 (iron scale)
Actually, iron is usually called its alloys with a low content of impurities (up to 0.8%), which retain the softness and ductility of a pure metal. But in practice, alloys of iron with carbon are more often used: steel (up to 2.14 wt.% carbon) and cast iron (more than 2.14 wt.% carbon), as well as stainless (alloyed) steel with the addition of alloying metals (chromium, manganese, nickel etc.). The combination of the specific properties of iron and its alloys make it "metal No. 1" in importance to humans.
In nature, iron is rarely found in its pure form, most often it occurs as part of iron-nickel meteorites. The prevalence of iron in the earth's crust is 4.65% (4th place after O, Si, Al). It is also believed that iron makes up most of the earth's core.
2.Properties
1.Physical St. Iron is a typical metal, in the free state it is silvery-white in color with a grayish tint. Pure metal is ductile, various impurities (in particular, carbon) increase its hardness and brittleness. It has pronounced magnetic properties. The so-called "iron triad" is often distinguished - a group of three metals (iron Fe, cobalt Co, nickel Ni) that have similar physical properties, atomic radii and electronegativity values.
2.Chemical St. Islands.
|
Oxidation state |
Oxide |
Hydroxide |
Character |
Notes |
|
Weakly basic | ||||
|
Very weak base, sometimes amphoteric | ||||
|
Not received |
|
Acid |
Strong oxidizing agent |
For iron, the oxidation states of iron are characteristic - +2 and +3.
The oxidation state +2 corresponds to black oxide FeO and green hydroxide Fe(OH) 2 . They are basic. In salts, Fe(+2) is present as a cation. Fe(+2) is a weak reducing agent.
+3 oxidation states correspond to red-brown Fe 2 O 3 oxide and brown Fe(OH) 3 hydroxide. They are amphoteric in nature, although their acidic and basic properties are weakly expressed. So, Fe 3+ ions are completely hydrolyzed even in an acidic environment. Fe (OH) 3 dissolves (and even then not completely), only in concentrated alkalis. Fe 2 O 3 reacts with alkalis only when fused, giving ferrites(formal salts of an acid that does not exist in the free form of acid HFeO 2):
Iron (+3) most often exhibits weak oxidizing properties.
The +2 and +3 oxidation states easily transition between themselves when the redox conditions change.
In addition, there is Fe 3 O 4 oxide, the formal oxidation state of iron in which is +8/3. However, this oxide can also be considered as iron (II) ferrite Fe +2 (Fe +3 O 2) 2 .
There is also an oxidation state of +6. The corresponding oxide and hydroxide do not exist in free form, but salts - ferrates (for example, K 2 FeO 4) have been obtained. Iron (+6) is in them in the form of an anion. Ferrates are strong oxidizing agents.
Pure metallic iron is stable in water and in dilute solutions. alkalis. Iron does not dissolve in cold concentrated sulfuric and nitric acids due to the passivation of the metal surface with a strong oxide film. Hot concentrated sulfuric acid, being a stronger oxidizing agent, interacts with iron.
With hydrochloric and diluted (about 20%) sulfuric acids iron reacts to form iron(II) salts:
When iron reacts with approximately 70% sulfuric acid when heated, the reaction proceeds with the formation iron(III) sulfate:
3. Oxides and hydroxides, CO and OM char-ka ...
Iron(II) compounds
Iron oxide (II) FeO has basic properties, it corresponds to the base Fe (OH) 2. Salts of iron (II) have a light green color. When stored, especially in moist air, they turn brown due to oxidation to iron (III). The same process occurs during storage of aqueous solutions of iron(II) salts:
Of iron(II) salts in aqueous solutions, stable mora salt- double ammonium and iron (II) sulfate (NH 4) 2 Fe (SO 4) 2 6H 2 O.
The reagent for Fe 2+ ions in solution can be potassium hexacyanoferrate(III) K 3 (red blood salt). When Fe 2+ and 3− ions interact, a precipitate turnbull blue:
For the quantitative determination of iron (II) in solution, use phenanthroline, which forms a red FePhen 3 complex with iron (II) in a wide pH range (4-9)
Iron(III) compounds
Iron(III) oxide Fe 2 O 3 weakly amphoterene, it corresponds to an even weaker than Fe (OH) 2, base Fe (OH) 3, which reacts with acids:
Fe 3+ salts tend to form crystalline hydrates. In them, the Fe 3+ ion is usually surrounded by six water molecules. Such salts are pink or purple in color. The Fe 3+ ion is completely hydrolyzed even in an acidic environment. At pH>4, this ion is almost completely precipitated in the form of Fe (OH) 3:
With partial hydrolysis of the Fe 3+ ion, polynuclear oxo- and hydroxocations are formed, due to which the solutions become brown. The main properties of iron (III) hydroxide Fe (OH) 3 are very weakly expressed. It is able to react only with concentrated alkali solutions:
The resulting iron(III) hydroxocomplexes are stable only in strongly alkaline solutions. When solutions are diluted with water, they are destroyed, and Fe (OH) 3 precipitates.
When fused with alkalis and oxides of other metals, Fe 2 O 3 forms a variety of ferrites:
Iron(III) compounds in solutions are reduced by metallic iron:
Iron(III) is capable of forming double sulfates with singly charged cations type alum, for example, KFe (SO 4) 2 - potassium iron alum, (NH 4) Fe (SO 4) 2 - iron ammonium alum, etc.
For qualitative detection of iron(III) compounds in a solution, a qualitative reaction of Fe 3+ ions with thiocyanate ions is used SCN − . When Fe 3+ ions interact with SCN − anions, a mixture of bright red iron thiocyanate complexes 2+ , + , Fe(SCN) 3 , - is formed. The composition of the mixture (and hence the intensity of its color) depends on various factors, so this method is not applicable for an accurate qualitative determination of iron.
Another high-quality reagent for Fe 3+ ions is potassium hexacyanoferrate(II) K 4 (yellow blood salt). When Fe 3+ and 4− ions interact, a bright blue precipitate is formed prussian blue:
Iron(VI) compounds
ferrates- salts of iron acid H 2 FeO 4 that do not exist in free form. These are violet-colored compounds, reminiscent of permanganates in oxidizing properties, and sulfates in solubility. Ferrates are obtained by the action of gaseous chlorine or ozone on a suspension of Fe (OH) 3 in alkali , for example, potassium ferrate (VI) K 2 FeO 4 . Ferrates are colored purple.
Ferrates can also be obtained electrolysis 30% alkali solution on an iron anode:
Ferrates are strong oxidizing agents. In an acidic environment, they decompose with the release of oxygen:
The oxidizing properties of ferrates are used to water disinfection.
4.Biorol
1) In living organisms, iron is an important trace element that catalyzes the processes of oxygen exchange (respiration).
2) Iron is usually included in enzymes in the form of a complex. In particular, this complex is present in hemoglobin, the most important protein that provides oxygen transport with blood to all organs of humans and animals. And it is he who stains the blood in a characteristic red color.
4) An excessive dose of iron (200 mg and above) can have a toxic effect. An overdose of iron depresses the antioxidant system of the body, so it is not recommended for healthy people to use iron preparations.