Iron is one of the most common chemical elements on earth. Since ancient times, people have learned to use it to facilitate their work. With the development of technology, its scope has expanded significantly. If several thousand years ago iron was used only for the manufacture of simple tools used for cultivating the land, now this chemical element is used in almost all areas of high-tech industries.

As Pliny the Elder wrote. “Iron miners provide man with the most excellent and most harmful tool. For with this tool we cut through the earth, we cultivate fertile gardens and, cutting wild vines with grapes, we force them to succumb every year. With this tool we build houses, break stones and use iron for all such needs. But with the same iron we carry out battles, battles and robberies, and we use it not only near, but we carry winged afar either from loopholes, or from powerful hands, or in the form of feathered arrows. The most vicious, in my opinion, is a trick of the human mind. For in order that death befall man sooner, they made it winged, and gave iron feathers. For this reason, let the guilt be attributed to man, and not to nature. Very often it is used for the manufacture of various alloys, the composition of which includes iron in different proportions. The best known of these alloys are steel and cast iron.

Electricity melts iron

The properties of steels are varied. There are steels designed for a long stay in sea water, steels that can withstand high temperatures and the aggressive action of hot gases, steels from which soft tie wires are made, and steels for making elastic and hard springs ...

Such a variety of properties results from the variety of steel compositions. So, from steel containing 1% carbon and 1.5% chromium, high-strength ball bearings are made; steel containing 18% chromium and 89% nickelis the well-known "stainless steel", and steel containing 18% tungsten, 4% chromium and 1% vanadiummake turning tools.

This variety of steel compositions makes them very difficult to smelt. Indeed, in an open-hearth furnace and a converter, the atmosphere is oxidizing, and elements such as chromium are easily oxidized and turn into slag, i.e., are lost. This means that in order to obtain steel with a chromium content of 18%, much more chromium must be fed into the furnace than 180 kg per ton of steel. Chrome is an expensive metal. How to find a way out of this situation?

A way out was found at the beginning of the 20th century. For metal smelting, it was proposed to use the heat of an electric arc. Scrap metal was loaded into a circular furnace, cast iron was poured and carbon or graphite electrodes were lowered. Between them and the metal in the furnace ("bath") an electric arc with a temperature of about 4000°C. The metal melted easily and quickly. And in such a closed electric furnace, you can create any atmosphere - oxidizing, reducing or completely neutral. In other words, valuable items can be prevented from burning out. This is how the metallurgy of high-quality steels was created.

Later, another method of electric melting was proposed - induction. It is known from physics that if a metal conductor is placed in a coil through which a high-frequency current passes, then a current is induced in it and the conductor heats up. This heat is enough to melt the metal in a certain time. The induction furnace consists of a crucible with a spiral embedded in the lining. A high-frequency current is passed through the spiral, and the metal in the crucible is melted. In such a furnace, you can also create any atmosphere.

In electric arc furnaces, the melting process usually takes place in several stages. First, unnecessary impurities are burned out of the metal, oxidizing them (oxidation period). Then, slag containing oxides of these elements is removed (downloaded) from the furnace, and forroalloys are loaded - iron alloys with elements that need to be introduced into the metal. The furnace is closed and melting is continued without air access (recovery period). As a result, the steel is saturated with the required elements in a given amount. The finished metal is released into a ladle and poured.

Steels, especially high-quality ones, turned out to be very sensitive to the content of impurities. Even small amounts of oxygen, nitrogen, hydrogen, sulfur, phosphorus greatly impair their properties - strength, toughness, corrosion resistance. These impurities form non-metallic compounds with iron and other elements contained in the steel, which wedged between the grains of the metal, impair its uniformity and reduce quality. So, with an increased content of oxygen and nitrogen in steels, their strength decreases, hydrogen causes the appearance of flakes - microcracks in the metal, which lead to unexpected destruction of steel parts under load, phosphorus increases the brittleness of steel in the cold, sulfur causes red brittleness - the destruction of steel under load at high temperatures.

Metallurgists have been looking for ways to remove these impurities for a long time. After smelting in open-hearth furnaces, converters and electric furnaces, the metal is deoxidized - aluminum, ferrosilicon (an alloy of iron with silicon) or ferromanganese are added to it. These elements actively combine with oxygen, float into the slag and reduce the oxygen content in the steel. But oxygen still remains in the steel, and for high-quality steels, its remaining quantities are too large. It was necessary to find other, more effective ways.

In the 1950s, metallurgists began to evacuate steel on an industrial scale. A ladle with liquid metal is placed in a chamber from which air is pumped out. The metal begins to boil violently and gases are released from it. However, imagine a ladle with 300 tons of steel and estimate how long it will take until it boils completely, and how much the metal will cool during this time.

It will immediately become clear to you that this method is suitable only for small amounts of steel. Therefore, other, faster and more efficient vacuuming methods have been developed. Now they are used in all developed countries, and this has improved the quality of steel. But the requirements for it all grew and grew.

In the early 60s in Kyiv, at the All-Union Institute of Electric Welding. E. O. Paton, a method of electroslag remelting of steel was developed, which very soon began to be used in many countries. This method is very simple. In a water-cooled metal vessel - a mold - an ingot of metal is placed, which must be purified, and covered with slag of a special composition. Then the ingot is connected to a current source. An electric arc occurs at the end of the ingot, and the metal begins to melt. Liquid steel reacts with slag and is purified not only from oxides, but also from nitrides, phosphides and sulfides. A new ingot, purified from harmful impurities, solidifies in the mold. In 1963, for the development and implementation of the method of electroslag remelting, a group of workers from the All-Union Institute of Electric Welding, headed by B. I. Medovar and Yu. V. Latash, was awarded the Lenin Prize.

A slightly different path was taken by metallurgical scientists from the Central Research Institute of Ferrous Metallurgy. I. P. Bardina. In collaboration with metallurgical workers, they developed an even simpler method. Slags of a special composition for cleaning metal are melted and poured into a ladle, and then metal is released from the furnace into this liquid slag. The slag mixes with the metal and absorbs impurities. This method is fast, efficient and does not require large amounts of electricity. Its authors S. G. Voinov, A. I. Osipov, A. G. Shalimov and others were also awarded the Lenin Prize in 1966.

However, the reader probably already has a question: why all these difficulties? After all, we have already said that in a conventional electric oven you can create any atmosphere. This means that you can simply pump air out of the furnace and melt in a vacuum. But do not rush to the patent office! This method has long been used in small induction furnaces, and in the late 60s and early 70s it began to be used in fairly large electric arc and induction furnaces. Now, the methods of vacuum arc and vacuum induction remelting have become quite widespread in industrialized countries.

Here we have described only the main methods of cleaning steel from harmful impurities. There are dozens of their varieties. They help metallurgists remove the notorious fly in the ointment from a barrel of honey and get high-quality metal.

How to get iron without blast furnaces

It has already been said above that ferrous metallurgy from the point of view of a chemist is, to put it mildly, an illogical occupation. First, iron is saturated with carbon and other elements, and then a lot of labor and energy are spent to burn out these elements. Isn't it easier to immediately recover iron from ore. After all, this is exactly what the ancient metallurgists did, who received softened hot spongy iron in raw forges. In recent years, this point of view has already moved beyond the stage of rhetorical questions and is based on completely real and even implemented projects. Obtaining iron directly from the ore, bypassing the blast-furnace process, was engaged in the last century. Then this process was called direct reduction. However, until recently, it has not found wide distribution. Firstly, all proposed methods of direct reduction were inefficient, and secondly, the resulting product - sponge iron - was of poor quality and contaminated with impurities. And yet enthusiasts continued to work in this direction.

The situation has changed radically since the widespread use of natural gas in industry. It proved to be an ideal means of recovering iron ore. The main component of natural gas - methane CH 4 - is decomposed by oxidation in the presence of a catalyst in special apparatuses - reformers according to the reaction 2CH 4 + O 2 → 2CO + 2H 2.

It turns out a mixture of reducing gases - carbon monoxide and hydrogen. This mixture enters the reactor, which is fed with iron ore. Let's make a reservation right away - the forms and designs of reactors are very diverse. Sometimes the reactor is a rotating tubular cement type kiln, sometimes a shaft kiln, sometimes a closed retort. This explains the variety of names for direct reduction methods: Midrex, Purofer, Ohalata-i-Lamina, SL-RN, etc. The number of methods has already exceeded two dozen. But their essence is usually the same. Rich iron ore is reduced by a mixture of carbon monoxide and hydrogen.

But what to do with the received products? From sponge iron, not only a good ax - a good nail cannot be forged. No matter how rich the original ore is, pure iron will still not come out of it. According to the laws of chemical thermodynamics, it will not even be possible to restore all the iron contained in the ore; some of it will still remain in the product in the form of oxides. And here a tried friend comes to the rescue - an electric furnace. Sponge iron turns out to be an almost ideal raw material for electrometallurgy. It contains few harmful impurities and melts well.

So, again, a two-step process! But this is another way. The benefit of the direct reduction scheme - the electric furnace is its low cost. Direct reduction plants are much cheaper and use less energy than blast furnaces. Such a blast-furnace steelmaking technology was included in the project of the Oskol Electrometallurgical Plant.

In our country, near Stary Oskol, a large metallurgical plant is being built, which will work exactly according to this scheme. Its first phase has already been put into operation. Note that direct remelting is not the only way to use sponge iron in ferrous metallurgy. It can also be used as a substitute for scrap metal in open hearth furnaces, converters and electric arc furnaces.

The method of remelting sponge iron in electric furnaces is also rapidly spreading abroad, especially in countries with large reserves of oil and natural gas, that is, in Latin America and the Middle East. However, already on the basis of these considerations (the availability of natural gas), there is still no reason to believe that the new method will ever completely replace the traditional two-stage method - a blast furnace - a steelmaking unit.

The future of iron

The Iron Age continues. Approximately 90% of all metals and alloys used by mankind are iron-based alloys. Iron is smelted in the world about 50 times more than aluminum, not to mention other metals. Plastics? But in our time, they most often play an independent role in various designs, and if, in accordance with tradition, they are trying to introduce them into the rank of “irreplaceable substitutes”, then more often they replace non-ferrous metals, not ferrous ones. Only a few percent of the plastics we consume are replacing steel.

Iron-based alloys are universal, technologically advanced, available and cheap in bulk. The raw material base of this metal also does not cause concern: already explored reserves of iron ore would be enough for at least two centuries to come. Iron has long to be the foundation of civilization.

Iron is an element of a secondary subgroup of the eighth group of the fourth period of the periodic system of chemical elements of D. I. Mendeleev 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). Medium activity metal, reducing agent.

Main oxidation states - +2, +3

The 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. In pure oxygen, iron burns, and in a finely dispersed state, it ignites spontaneously in air.

Chemical properties of a simple substance - iron:

Rusting and burning in oxygen

1) In air, iron is easily oxidized in the presence of moisture (rusting):

4Fe + 3O 2 + 6H 2 O → 4Fe(OH) 3

A heated iron wire burns in oxygen, forming scale - iron oxide (II, III):

3Fe + 2O 2 → Fe 3 O 4

3Fe + 2O 2 → (Fe II Fe 2 III) O 4 (160 ° С)

2) At high temperatures (700–900°C), iron reacts with water vapor:

3Fe + 4H 2 O - t ° → Fe 3 O 4 + 4H 2

3) Iron reacts with non-metals when heated:

2Fe+3Cl 2 →2FeCl 3 (200 °С)

Fe + S – t° → FeS (600 °C)

Fe + 2S → Fe +2 (S 2 -1) (700 ° С)

4) In a series of voltages, it is to the left of hydrogen, reacts with dilute acids Hcl and H 2 SO 4, while iron (II) salts are formed and hydrogen is released:

Fe + 2HCl → FeCl 2 + H 2 (reactions are carried out without air access, otherwise Fe +2 is gradually converted by oxygen into Fe +3)

Fe + H 2 SO 4 (diff.) → FeSO 4 + H 2

In concentrated oxidizing acids, iron dissolves only when heated, it immediately passes into the Fe 3+ cation:

2Fe + 6H 2 SO 4 (conc.) – t° → Fe 2 (SO 4) 3 + 3SO 2 + 6H 2 O

Fe + 6HNO 3 (conc.) – t° → Fe(NO 3) 3 + 3NO 2 + 3H 2 O

(in the cold, concentrated nitric and sulfuric acids passivate

An iron nail immersed in a bluish solution of copper sulphate is gradually covered with a coating of red metallic copper.

5) Iron displaces metals to the right of it in solutions of their salts.

Fe + CuSO 4 → FeSO 4 + Cu

Amphotericity of iron is manifested only in concentrated alkalis during boiling:

Fe + 2NaOH (50%) + 2H 2 O \u003d Na 2 ↓ + H 2

and a precipitate of sodium tetrahydroxoferrate(II) is formed.

Technical iron- alloys of iron with carbon: cast iron contains 2.06-6.67% C, steel 0.02-2.06% C, other natural impurities (S, P, Si) and artificially introduced special additives (Mn, Ni, Cr) are often present, which gives iron alloys technically useful properties - hardness, thermal and corrosion resistance, malleability, etc. .

Blast furnace iron production process

The blast-furnace process of iron production consists of the following stages:

a) preparation (roasting) of sulfide and carbonate ores - conversion to oxide ore:

FeS 2 → Fe 2 O 3 (O 2, 800 ° С, -SO 2) FeCO 3 → Fe 2 O 3 (O 2, 500-600 ° С, -CO 2)

b) burning coke with hot blast:

C (coke) + O 2 (air) → CO 2 (600-700 ° C) CO 2 + C (coke) ⇌ 2CO (700-1000 ° C)

c) reduction of oxide ore with carbon monoxide CO in succession:

Fe2O3 →(CO)(Fe II Fe 2 III) O 4 →(CO) FeO →(CO) Fe

d) carburization of iron (up to 6.67% C) and melting of cast iron:

Fe (t ) →(C(coke)900-1200°С) Fe (g) (cast iron, t pl 1145°C)

In cast iron, cementite Fe 2 C and graphite are always present in the form of grains.

Steel production

The redistribution of cast iron into steel is carried out in special furnaces (converter, open-hearth, electric), which differ in the method of heating; process temperature 1700-2000 °C. Blowing oxygen-enriched air burns out excess carbon from cast iron, as well as sulfur, phosphorus and silicon in the form of oxides. In this case, oxides are either captured in the form of exhaust gases (CO 2, SO 2), or are bound into an easily separated slag - a mixture of Ca 3 (PO 4) 2 and CaSiO 3. To obtain special steels, alloying additives of other metals are introduced into the furnace.

Receipt pure iron in industry - electrolysis of a solution of iron salts, for example:

FeCl 2 → Fe↓ + Cl 2 (90°C) (electrolysis)

(there are other special methods, including the reduction of iron oxides with hydrogen).

Pure iron is used in the production of special alloys, in the manufacture of cores of electromagnets and transformers, cast iron is used in the production of castings and steel, steel is used as structural and tool materials, including wear-, heat- and corrosion-resistant materials.

Iron(II) oxide F EO . Amphoteric oxide with a large predominance of basic properties. Black, has an ionic structure of Fe 2+ O 2-. When heated, it first decomposes, then re-forms. It is not formed during the combustion of iron in air. Does not react with water. Decomposed by acids, fused with alkalis. Slowly oxidizes in moist air. Recovered by hydrogen, coke. Participates in the blast-furnace process of iron smelting. It is used as a component of ceramics and mineral paints. Equations of the most important reactions:

4FeO ⇌ (Fe II Fe 2 III) + Fe (560-700 ° С, 900-1000 ° С)

FeO + 2HC1 (razb.) \u003d FeC1 2 + H 2 O

FeO + 4HNO 3 (conc.) \u003d Fe (NO 3) 3 + NO 2 + 2H 2 O

FeO + 4NaOH \u003d 2H 2 O + Na 4FeO3(red.) trioxoferrate(II)(400-500 °С)

FeO + H 2 \u003d H 2 O + Fe (high purity) (350 ° C)

FeO + C (coke) \u003d Fe + CO (above 1000 ° C)

FeO + CO \u003d Fe + CO 2 (900 ° C)

4FeO + 2H 2 O (moisture) + O 2 (air) → 4FeO (OH) (t)

6FeO + O 2 \u003d 2 (Fe II Fe 2 III) O 4 (300-500 ° С)

Receipt in laboratories: thermal decomposition of iron (II) compounds without air access:

Fe (OH) 2 \u003d FeO + H 2 O (150-200 ° C)

FeSOz \u003d FeO + CO 2 (490-550 ° С)

Diiron oxide (III) - iron ( II ) ( Fe II Fe 2 III) O 4 . Double oxide. Black, has the ionic structure of Fe 2+ (Fe 3+) 2 (O 2-) 4. Thermally stable up to high temperatures. Does not react with water. Decomposed by acids. It is reduced by hydrogen, red-hot iron. Participates in the blast-furnace process of iron production. It is used as a component of mineral paints ( minium iron), ceramics, colored cement. The product of special oxidation of the surface of steel products ( blackening, bluing). The composition corresponds to brown rust and dark scale on iron. The use of the Fe 3 O 4 formula is not recommended. Equations of the most important reactions:

2 (Fe II Fe 2 III) O 4 \u003d 6FeO + O 2 (above 1538 ° С)

(Fe II Fe 2 III) O 4 + 8HC1 (razb.) \u003d FeC1 2 + 2FeC1 3 + 4H 2 O

(Fe II Fe 2 III) O 4 + 10HNO 3 (conc.) \u003d 3 Fe (NO 3) 3 + NO 2 + 5H 2 O

(Fe II Fe 2 III) O 4 + O 2 (air) \u003d 6Fe 2 O 3 (450-600 ° С)

(Fe II Fe 2 III) O 4 + 4H 2 \u003d 4H 2 O + 3Fe (high purity, 1000 ° C)

(Fe II Fe 2 III) O 4 + CO \u003d 3 FeO + CO 2 (500-800 ° C)

(Fe II Fe 2 III) O4 + Fe ⇌4 FeO (900-1000 ° С, 560-700 ° С)

Receipt: combustion of iron (see) in air.

magnetite.

Iron(III) oxide F e 2 O 3 . Amphoteric oxide with a predominance of basic properties. Red-brown, has an ionic structure (Fe 3+) 2 (O 2-) 3. Thermally stable up to high temperatures. It is not formed during the combustion of iron in air. Does not react with water, a brown amorphous hydrate Fe 2 O 3 nH 2 O precipitates from the solution. Slowly reacts with acids and alkalis. It is reduced by carbon monoxide, molten iron. Alloys with oxides of other metals and forms double oxides - spinels(technical products are called ferrites). It is used as a raw material in iron smelting in the blast furnace process, as a catalyst in the production of ammonia, as a component of ceramics, colored cements and mineral paints, in thermite welding of steel structures, as a sound and image carrier on magnetic tapes, as a polishing agent for steel and glass.

Equations of the most important reactions:

6Fe 2 O 3 \u003d 4 (Fe II Fe 2 III) O 4 + O 2 (1200-1300 ° С)

Fe 2 O 3 + 6HC1 (razb.) → 2FeC1 3 + ZH 2 O (t) (600 ° C, p)

Fe 2 O 3 + 2NaOH (conc.) → H 2 O+ 2 NbutFeO 2 (red)dioxoferrate(III)

Fe 2 O 3 + MO \u003d (M II Fe 2 II I) O 4 (M \u003d Cu, Mn, Fe, Ni, Zn)

Fe 2 O 3 + ZN 2 \u003d ZN 2 O + 2Fe (highly pure, 1050-1100 ° С)

Fe 2 O 3 + Fe \u003d ZFeO (900 ° C)

3Fe 2 O 3 + CO \u003d 2 (Fe II Fe 2 III) O 4 + CO 2 (400-600 ° С)

Receipt in the laboratory - thermal decomposition of iron (III) salts in air:

Fe 2 (SO 4) 3 \u003d Fe 2 O 3 + 3SO 3 (500-700 ° С)

4 (Fe (NO 3) 3 9 H 2 O) \u003d 2 Fe a O 3 + 12NO 2 + 3O 2 + 36H 2 O (600-700 ° С)

In nature - iron oxide ores hematite Fe 2 O 3 and limonite Fe 2 O 3 nH 2 O

Iron(II) hydroxide F e(OH) 2 . Amphoteric hydroxide with a predominance of basic properties. White (sometimes with a greenish tinge), Fe-OH bonds are predominantly covalent. Thermally unstable. Easily oxidizes in air, especially when wet (darkens). Insoluble in water. Reacts with dilute acids, concentrated alkalis. Typical restorer. An intermediate product in the rusting of iron. It is used in the manufacture of the active mass of iron-nickel batteries.

Equations of the most important reactions:

Fe (OH) 2 \u003d FeO + H 2 O (150-200 ° C, in atm.N 2)

Fe (OH) 2 + 2HC1 (razb.) \u003d FeC1 2 + 2H 2 O

Fe (OH) 2 + 2NaOH (> 50%) \u003d Na 2 ↓ (blue-green) (boiling)

4Fe(OH) 2 (suspension) + O 2 (air) → 4FeO(OH)↓ + 2H 2 O (t)

2Fe (OH) 2 (suspension) + H 2 O 2 (razb.) \u003d 2FeO (OH) ↓ + 2H 2 O

Fe (OH) 2 + KNO 3 (conc.) \u003d FeO (OH) ↓ + NO + KOH (60 ° С)

Receipt: precipitation from solution with alkalis or ammonia hydrate in an inert atmosphere:

Fe 2+ + 2OH (razb.) = Fe(OH) 2 ↓

Fe 2+ + 2 (NH 3 H 2 O) = Fe(OH) 2 ↓+ 2NH4

Iron metahydroxide F eO(OH). Amphoteric hydroxide with a predominance of basic properties. Light brown, Fe-O and Fe-OH bonds are predominantly covalent. When heated, it decomposes without melting. Insoluble in water. It precipitates from solution in the form of a brown amorphous polyhydrate Fe 2 O 3 nH 2 O, which, when kept under a dilute alkaline solution or when dried, turns into FeO (OH). Reacts with acids, solid alkalis. Weak oxidizing and reducing agent. Sintered with Fe(OH) 2 . An intermediate product in the rusting of iron. It is used as a base for yellow mineral paints and enamels, as an exhaust gas absorber, as a catalyst in organic synthesis.

Connection composition Fe(OH) 3 is not known (not obtained).

Equations of the most important reactions:

Fe 2 O 3 . nH 2 O→( 200-250 °С, —H 2 O) FeO(OH)→( 560-700°C in air, -H2O)→Fe 2 O 3

FeO (OH) + ZNS1 (razb.) \u003d FeC1 3 + 2H 2 O

FeO(OH)→ Fe 2 O 3 . nH 2 O-colloid(NaOH (conc.))

FeO(OH)→ Na 3 [Fe(OH) 6 ]White, Na 5 and K 4, respectively; in both cases, a blue product of the same composition and structure, KFe III, precipitates. In the laboratory, this precipitate is called Prussian blue, or turnbull blue:

Fe 2+ + K + + 3- = KFe III ↓

Fe 3+ + K + + 4- = KFe III ↓

Chemical names of initial reagents and reaction product:

K 3 Fe III - potassium hexacyanoferrate (III)

K 4 Fe III - potassium hexacyanoferrate (II)

KFe III - hexacyanoferrate (II) iron (III) potassium

In addition, the thiocyanate ion NCS - is a good reagent for Fe 3+ ions, iron (III) combines with it, and a bright red ("bloody") color appears:

Fe 3+ + 6NCS - = 3-

With this reagent (for example, in the form of KNCS salt), even traces of iron (III) can be detected in tap water if it passes through iron pipes covered with rust from the inside.

History

Iron as an instrumental material has been known since ancient times. The oldest iron products found during archaeological excavations date back to the 4th millennium BC. e. and belong to the ancient Sumerian and ancient Egyptian civilizations. These are made of meteorite iron, that is, an alloy of iron and nickel (the content of the latter ranges from 5 to 30%), jewelry from Egyptian tombs (about 3800 BC) and a dagger from the Sumerian city of Ur (about 3100 BC). e.). Apparently, one of the names of iron in Greek and Latin comes from the celestial origin of meteoric iron: “sider” (which means “starry”).

Products from iron obtained by smelting have been known since the time of the settlement of the Aryan tribes from Europe to Asia, the islands of the Mediterranean Sea, and beyond (the end of the 4th and 3rd millennium BC). The oldest known iron tools are steel blades found in the masonry of the pyramid of Cheops in Egypt (built around 2530 BC). As excavations in the Nubian desert have shown, already in those days the Egyptians, trying to separate the mined gold from heavy magnetite sand, calcined ore with bran and similar substances containing carbon. As a result, a layer of doughy iron floated on the surface of the gold melt, which was processed separately. Tools were forged from this iron, including those found in the pyramid of Cheops. However, after the grandson of Cheops Menkaur (2471-2465 BC), turmoil occurred in Egypt: the nobility, led by the priests of the god Ra, overthrew the ruling dynasty, and a leapfrog of usurpers began, ending with the accession of the pharaoh of the next dynasty, Userkar, whom the priests declared to be the son and incarnation the god Ra himself (since then this has become the official status of the pharaohs). During this turmoil, the cultural and technical knowledge of the Egyptians fell into decay, and, just as the art of building the pyramids degraded, the technology of iron production was lost, to the point that later, mastering the Sinai Peninsula in search of copper ore, the Egyptians did not pay any attention to iron ore deposits there, but received iron from neighboring Hittites and Mitannians.

The first mastered the production of iron Hatt, this is indicated by the oldest (2nd millennium BC) mention of iron in the texts of the Hittites, who founded their empire on the territory of the Hatt (modern Anatolia in Turkey). So, in the text of the Hittite king Anitta (about 1800 BC) it says:

When I went on a campaign to the city of Puruskhanda, a man from the city of Puruskhanda came to bow to me (...?) and he presented me with 1 iron throne and 1 iron scepter (?) as a sign of humility (?) ...

(a source: Giorgadze G. G.// Bulletin of ancient history. 1965. No. 4.)

In ancient times, khalibs were reputed to be masters of iron products. The legend of the Argonauts (their campaign to Colchis took place about 50 years before the Trojan War) tells that the king of Colchis, Eet, gave Jason an iron plow to plow the field of Ares, and describes his subjects, the halibers:

They do not plow the land, do not plant fruit trees, do not graze herds in rich meadows; they extract ore and iron from the uncultivated land and barter food for them. The day does not begin for them without hard work, they spend in the darkness of the night and thick smoke, working all day ...

Aristotle described their method of obtaining steel: “the Khalibs washed the river sand of their country several times - thereby separating black concentrate (a heavy fraction consisting mainly of magnetite and hematite), and melted it in furnaces; the metal thus obtained had a silvery color and was stainless."

Magnetite sands, which are often found along the entire coast of the Black Sea, were used as raw materials for steel smelting: these magnetite sands consist of a mixture of fine grains of magnetite, titanium-magnetite or ilmenite, and fragments of other rocks, so that the steel smelted by the Khalibs was alloyed, and had excellent properties. Such a peculiar way of obtaining iron suggests that the Khalibs only spread iron as a technological material, but their method could not be a method for the widespread industrial production of iron products. However, their production served as an impetus for the further development of iron metallurgy.

In the deepest antiquity, iron was valued more than gold, and according to the description of Strabo, African tribes gave 10 pounds of gold for 1 pound of iron, and according to the studies of the historian G. Areshyan, the cost of copper, silver, gold and iron among the ancient Hittites was in the ratio 1: 160 : 1280: 6400. In those days, iron was used as a jewelry metal, thrones and other regalia of royal power were made from it: for example, in the biblical book Deuteronomy 3.11, the “iron bed” of the Rephaim king Og is described.

In the tomb of Tutankhamen (circa 1350 BC) was found a dagger made of iron in a gold frame - possibly a gift from the Hittites for diplomatic purposes. But the Hittites did not strive for the widespread dissemination of iron and its technologies, which is also evident from the correspondence of the Egyptian pharaoh Tutankhamun and his father-in-law Hattusil, the king of the Hittites, that has come down to us. The pharaoh asks to send more iron, and the king of the Hittites evasively answers that the iron reserves have run out, and the blacksmiths are busy with agricultural work, so he cannot fulfill the request of the royal son-in-law, and sends only one dagger from “good iron” (that is, steel). As you can see, the Hittites tried to use their knowledge to achieve military advantages, and did not give others the opportunity to catch up with them. Apparently, therefore, iron products became widespread only after the Trojan War and the fall of the Hittites, when, thanks to the trading activity of the Greeks, iron technology became known to many, and new iron deposits and mines were discovered. So the Bronze Age was replaced by the Iron Age.

According to Homer's descriptions, although during the Trojan War (circa 1250 BC) weapons were mostly made of copper and bronze, iron was already well known and in great demand, although more as a precious metal. For example, in the 23rd song of the Iliad, Homer says that Achilles awarded the winner in a discus throwing competition with an iron cry disc. The Achaeans mined this iron from the Trojans and neighboring peoples (Iliad 7.473), including from the Khalibs, who fought on the side of the Trojans:

“Other men of the Achaeans bought wine with me,
Those for ringing copper, for gray iron changed,
Those for ox-skins or high-horned oxen,
Those for their captives. And a merry feast is prepared ... "

Perhaps iron was one of the reasons that prompted the Achaean Greeks to move to Asia Minor, where they learned the secrets of its production. And excavations in Athens showed that already around 1100 BC. e. and later iron swords, spears, axes, and even iron nails were already widespread. The biblical book of Joshua 17:16 (cf. Judges 14:4) describes that the Philistines (the biblical "PILISTIM", and these were proto-Greek tribes related to the later Hellenes, mainly Pelasgians) had many iron chariots, that is, in this iron has already become widely used in large quantities.

Homer in the Iliad and the Odyssey calls iron "a hard metal", and describes the hardening of tools:

“A quick forger, having made an ax or an ax,
Metal into the water, heating it up so that it doubles
He had a fortress, immerses ... "

Homer calls iron difficult, because in ancient times the main method of obtaining it was the raw-blowing process: alternating layers of iron ore and charcoal were calcined in special furnaces (forges - from the ancient "Horn" - a horn, a pipe, originally it was just a pipe dug in the ground , usually horizontally in the slope of a ravine). In the hearth, iron oxides are reduced to metal by hot coal, which takes away oxygen, oxidizing to carbon monoxide, and as a result of such calcination of ore with coal, doughy bloom (spongy) iron was obtained. Kritsu was cleaned of slag by forging, squeezing out impurities with strong hammer blows. The first hearths had a relatively low temperature - noticeably lower than the melting point of cast iron, so the iron turned out to be relatively low-carbon. In order to obtain strong steel, it was necessary to calcinate and forge the iron bar with coal many times, while the surface layer of the metal was additionally saturated with carbon and hardened. This was how “good iron” was obtained - and although it required a lot of work, the products obtained in this way were significantly stronger and harder than bronze ones.

Later, they learned how to make more efficient furnaces (in Russian - blast furnace, domnitsa) for steel production, and used furs to supply air to the furnace. Already the Romans were able to bring the temperature in the furnace to the melting of steel (about 1400 degrees, and pure iron melts at 1535 degrees). In this case, cast iron is formed with a melting point of 1100-1200 degrees, which is very brittle in the solid state (not even amenable to forging) and does not have the elasticity of steel. It was originally considered a harmful by-product. pig iron, in Russian, pig iron, ingots, where, in fact, the word cast iron comes from), but then it turned out that when remelted in a furnace with increased air blowing through it, cast iron turns into good quality steel, as excess carbon burns out. Such a two-stage process for the production of steel from cast iron turned out to be simpler and more profitable than bloomery, and this principle has been used without much change for many centuries, remaining to this day the main method for the production of iron materials.

Bibliography: Karl Bucks. Wealth of the earth's interior. M .: Progress, 1986, p. 244, chapter "Iron"

origin of name

There are several versions of the origin of the Slavic word "iron" (Belarusian zhalez, Ukrainian zalizo, old Slav. iron, bulg. iron, Serbohorv. zhezo, Polish. Zelazo, Czech železo, Slovenian zelezo).

One of the etymologies connects Praslav. *ZelEzo with the Greek word χαλκός , which meant iron and copper, according to another version *ZelEzo akin to words *zely"turtle" and *eye"rock", with the general seme "stone". The third version suggests an ancient borrowing from an unknown language.

The Germanic languages ​​borrowed the name iron (Gothic. eisarn, English iron, German Eisen, netherl. ijzer, dat. jern, swedish jarn) from Celtic.

Pra-Celtic word *isarno-(> OE iarn, OE Bret hoiarn), probably goes back to Proto-IE. *h 1 esh 2 r-no- "bloody" with the semantic development "bloody" > "red" > "iron". According to another hypothesis, this word goes back to pra-i.e. *(H)ish 2ro- "strong, holy, possessing supernatural power" .

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- stellar; 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 latin sidus, meaning "star", probably have a common origin.

isotopes

Natural iron consists of four stable isotopes: 54 Fe (isotopic abundance 5.845%), 56 Fe (91.754%), 57 Fe (2.119%) and 58 Fe (0.282%). More than 20 unstable isotopes of iron with mass numbers from 45 to 72 are also known, the most stable of which are 60 Fe (half-life according to data updated in 2009 is 2.6 million years), 55 Fe (2.737 years), 59 Fe ( 44.495 days) and 52 Fe (8.275 hours); the remaining isotopes have half-lives of less than 10 minutes.

The iron isotope 56 Fe is among the most stable nuclei: all of the following elements can reduce the binding energy per nucleon by decay, and all previous elements, in principle, could reduce the binding energy per nucleon due to fusion. It is believed that a series of synthesis of elements in the cores of normal stars ends with iron (see Iron star), and all subsequent elements can be formed only as a result of supernova explosions.

Geochemistry of iron

Hydrothermal source with ferruginous water. Iron oxides turn water brown

Iron is one of the most common elements in the solar system, especially on the terrestrial planets, in particular on Earth. A significant part of the iron of the terrestrial planets is located in the cores of the planets, where its content is estimated to be about 90%. The content of iron in the earth's crust is 5%, and in the mantle about 12%. Of the metals, iron is second only to aluminum in terms of abundance in the crust. At the same time, about 86% of all iron is in the core, and 14% in the mantle. The content of iron increases significantly in the igneous rocks of the basic composition, where it is associated with pyroxene, amphibole, olivine and biotite. In industrial concentrations, iron accumulates during almost all exogenous and endogenous processes occurring in the earth's crust. In sea water, iron is contained in very small amounts of 0.002-0.02 mg / l. In river water, it is slightly higher - 2 mg / l.

Geochemical properties of iron

The most important geochemical feature of iron is the presence of several oxidation states. Iron in a neutral form - metallic - composes the core of the earth, possibly present in the mantle and very rarely found in the earth's crust. Ferrous iron FeO is the main form of iron in the mantle and the earth's crust. Oxide iron Fe 2 O 3 is characteristic of the uppermost, most oxidized, parts of the earth's crust, in particular, sedimentary rocks.

In terms of crystal chemical properties, the Fe 2+ ion is close to the Mg 2+ and Ca 2+ ions, other main elements that make up a significant part of all terrestrial rocks. Due to their crystal chemical similarity, iron replaces magnesium and, in part, calcium in many silicates. The content of iron in minerals of variable composition usually increases with decreasing temperature.

iron minerals

A large number of ores and minerals containing iron are known. Of the greatest practical importance are red iron ore (hematite, Fe 2 O 3; contains up to 70% Fe), magnetic iron ore (magnetite, FeFe 2 O 4, Fe 3 O 4; contains 72.4% Fe), brown iron ore or limonite (goethite and hydrogoethite, FeOOH and FeOOH nH 2 O, respectively). Goethite and hydrogoethite are most often found in weathering crusts, forming the so-called "iron hats", the thickness of which reaches several hundred meters. They can also be of sedimentary origin, falling out of colloidal solutions in lakes or coastal areas of the seas. In this case, oolitic, or legume, iron ores are formed. Vivianite Fe 3 (PO 4) 2 8H 2 O is often found in them, forming black elongated crystals and radial-radiant aggregates.

Iron sulfides are also widespread in nature - pyrite FeS 2 (sulfur or iron pyrite) and pyrrhotite. They are not iron ore - pyrite is used to produce sulfuric acid, and pyrrhotite often contains nickel and cobalt.

In terms of iron ore reserves, Russia ranks first in the world. The content of iron in sea water is 1·10 −5 -1·10 −8%.

Other common iron minerals are:

• Siderite - FeCO 3 - contains approximately 35% iron. It has a yellowish-white (with a gray or brown tint in case of contamination) color. The density is 3 g / cm³ and the hardness is 3.5-4.5 on the Mohs scale.
• Marcasite - FeS 2 - contains 46.6% iron. It occurs in the form of yellow, like brass, bipyramidal rhombic crystals with a density of 4.6-4.9 g / cm³ and a hardness of 5-6 on the Mohs scale.
• Lollingite - FeAs 2 - contains 27.2% iron and occurs in the form of silver-white bipyramidal rhombic crystals. Density is 7-7.4 g / cm³, hardness is 5-5.5 on the Mohs scale.
• Mispikel - FeAsS - contains 34.3% iron. It occurs in the form of white monoclinic prisms with a density of 5.6-6.2 g / cm³ and a hardness of 5.5-6 on the Mohs scale.
• Melanterite - FeSO 4 7H 2 O - is less common in nature and is a green (or gray due to impurities) monoclinic crystals with a vitreous luster, fragile. The density is 1.8-1.9 g / cm³.
• Vivianite - Fe 3 (PO 4) 2 8H 2 O - occurs in the form of blue-gray or green-gray monoclinic crystals with a density of 2.95 g / cm³ and a hardness of 1.5-2 on the Mohs scale.

In addition to the above iron minerals, there are, for example:

Main deposits

According to the US Geological Survey (2011 estimate), the world's proven reserves of iron ore are about 178 billion tons. The main iron deposits are in Brazil (1st place), Australia, USA, Canada, Sweden, Venezuela, Liberia, Ukraine, France, India. In Russia, iron is mined at the Kursk Magnetic Anomaly (KMA), the Kola Peninsula, Karelia and Siberia. A significant role has recently been acquired by bottom oceanic deposits, in which iron, together with manganese and other valuable metals, is found in nodules.

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 (such as limestone) are fed in from above and are met by a stream of injected 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 a lack 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:

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. Iron melt 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:

,

while there is no contamination of 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.

Physical Properties

The phenomenon of polymorphism is extremely important for steel metallurgy. It is thanks to the α-γ transitions of the crystal lattice that the heat treatment of steel occurs. Without this phenomenon, iron as the basis of steel would not have received such widespread use.

Iron is a moderately refractory metal. In a series of standard electrode potentials, iron stands before hydrogen and easily reacts with dilute acids. Thus, iron belongs to the metals of medium activity.

The melting point of iron is 1539 °C, the boiling point is 2862 °C.

Chemical properties

Characteristic oxidation states

• Acid does not exist in its free form - only its salts have been obtained.

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. Thus, 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 a 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.

Properties of a simple substance

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 moist 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(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 the iron (II) salts in aqueous solutions, Mohr's salt is stable - double ammonium and iron (II) sulfate (NH 4) 2 Fe (SO 4) 2 6H 2 O.

Potassium hexacyanoferrate (III) K 3 (red blood salt) can serve as a reagent for Fe 2+ ions in solution. When Fe 2+ and 3− ions interact, turnbull blue precipitates:

For the quantitative determination of iron (II) in solution, phenanthroline Phen is used, which forms a red FePhen 3 complex with iron (II) (light absorption maximum - 520 nm) in a wide pH range (4-9).

Iron(III) compounds

Iron(III) compounds in solutions are reduced by metallic iron:

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.

For qualitative detection of iron(III) compounds in solution, the qualitative reaction of Fe 3+ ions with thiocyanate ions SCN − is used. 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 the 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 of Prussian blue precipitates:

Iron(VI) compounds

The oxidizing properties of ferrates are used to disinfect water.

Iron compounds VII and VIII

There are reports on the electrochemical preparation of iron(VIII) compounds. , , , however, there are no independent works confirming these results.

Application

Iron ore

Iron is one of the most used metals, accounting for up to 95% of the world's metallurgical production.

• Iron is the main component of steels and cast irons - the most important structural materials.
• Iron can be part of alloys based on other metals - for example, nickel.
• Magnetic iron oxide (magnetite) is an important material in the manufacture of long-term computer memory devices: hard drives, floppy disks, etc.
• Ultrafine magnetite powder is used in many black and white laser printers mixed with polymer granules as a toner. It uses both the black color of magnetite and its ability to adhere to a magnetized transfer roller.
• The unique ferromagnetic properties of a number of iron-based alloys contribute to their widespread use in electrical engineering for the magnetic cores of transformers and electric motors.
• Iron (III) chloride (ferric chloride) is used in amateur radio practice for etching printed circuit boards.
• Ferrous sulfate (iron sulfate) mixed with copper sulphate is used to control harmful fungi in gardening and construction.
• Iron is used as an anode in iron-nickel batteries, iron-air batteries.
• Aqueous solutions of chlorides of divalent and ferric iron, as well as its sulfates, are used as coagulants in the purification of natural and waste water in the water treatment of industrial enterprises.

The biological significance of iron

In living organisms, iron is an important trace element that catalyzes the processes of oxygen exchange (respiration). The body of an adult contains about 3.5 grams of iron (about 0.02%), of which 78% are the main active element of blood hemoglobin, the rest is part of the enzymes of other cells, catalyzing the processes of respiration in cells. Iron deficiency manifests itself as a disease of the body (chlorosis in plants and anemia in animals).

Normally, iron enters enzymes as a complex called heme. In particular, this complex is present in hemoglobin, the most important protein that ensures the transport of oxygen with blood to all organs of humans and animals. And it is he who stains the blood in a characteristic red color.

Iron complexes other than heme are found, for example, in the enzyme methane monooxygenase, which oxidizes methane to methanol, in the important enzyme ribonucleotide reductase, which is involved in DNA synthesis.

Inorganic iron compounds are found in some bacteria and are sometimes used by them to bind atmospheric nitrogen.

Iron enters the body of animals and humans with food (liver, meat, eggs, legumes, bread, cereals, beets are the richest in it). Interestingly, once spinach was erroneously included in this list (due to a typo in the analysis results - the “extra” zero after the decimal point was lost).

An excess dose of iron (200 mg or more) can be toxic. An overdose of iron depresses the antioxidant system of the body, so it is not recommended to use iron preparations for healthy people.

Notes

1. Chemical Encyclopedia: in 5 volumes / Ed.: Knunyants I. L. (chief editor). - M .: Soviet Encyclopedia, 1990. - T. 2. - S. 140. - 671 p. - 100,000 copies.
2. Karapetyants M. Kh., Drakin S. I. General and inorganic chemistry: Textbook for universities. - 4th ed., erased. - M.: Chemistry, 2000, ISBN 5-7245-1130-4, p. 529
3. M. Vasmer. Etymological dictionary of the Russian language. - Progress. - 1986. - T. 2. - S. 42-43.
4. Trubachev O. N. Slavic etymologies. // Questions of Slavic linguistics, No. 2, 1957.
5. Borys W. Slownik etymologiczny języka polskiego. - Krakow: Wydawnictwo Literackie. - 2005. - S. 753-754.
6. Walde A. Lateinisches etymologisches Wörterbuch. - Carl Winter's Universitätsbuchhandlung. - 1906. - S. 285.
7. Meye A. The main features of the Germanic group of languages. - URSS. - 2010. - S. 141.
8. Matasovic R. Etymological Dictionary of Proto-Celtic. - Brill. - 2009. - S. 172.
9. Mallory, J. P., Adams, D. Q. Encyclopedia of Indo-European Culture. - Fitzroy-Dearborn. - 1997. - P. 314.
10. "New Measurement of the 60 Fe Half-Life". Physical Review Letters 103 : 72502. DOI: 10.1103/PhysRevLett.103.072502 .
11. G. Audi, O. Bersillon, J. Blachot and A. H. Wapstra (2003). "The NUBASE evaluation of nuclear and decay properties". Nuclear Physics A 729 : 3–128. DOI:10.1016/j.nuclphysa.2003.11.001 .
12. Yu. M. Shirokov, N. P. Yudin. Nuclear physics. Moscow: Nauka, 1972. Chapter Nuclear space physics.
13. R. Ripan, I. Chetyanu. Inorganic chemistry // Chemistry of non-metals = Chimia metalelor. - Moscow: Mir, 1972. - T. 2. - S. 482-483. - 871 p.
14. Gold and Precious Metals
15. Metal science and heat treatment of steel. Ref. ed. In 3 volumes / Ed. M. L. Bershtein, A. G. Rakhshtadt. - 4th ed., revised. and additional T. 2. Fundamentals of heat treatment. In 2 books. Book. 1. M.: Metallurgiya, 1995. 336 p.
16. T. Takahashi & W.A. Bassett, "High-Pressure Polymorph of Iron," Science, Vol. 145 #3631, 31 Jul 1964, p 483-486.
17. Schilt A. Analytical Application of 1,10-phenantroline and Related Compounds. Oxford, Pergamon Press, 1969.
18. Lurie Yu. Yu. Handbook of analytical chemistry. M., Chemistry, 1989. S. 297.
19. Lurie Yu. Yu. Handbook of analytical chemistry. M., Chemistry, 1989, S. 315.
20. Brower G. (ed.) Guide to inorganic synthesis. v. 5. M., Mir, 1985. S. 1757-1757.
21. Remy G. Course of inorganic chemistry. vol. 2. M., Mir, 1966. S. 309.
22. Kiselev Yu. M., Kopelev N. S., Spitsyn V. I., Martynenko L. I. Octal iron // Dokl. Academy of Sciences of the USSR. 1987. T.292. pp.628-631
23. Perfil'ev Yu. D., Kopelev N. S., Kiselev Yu. Academy of Sciences of the USSR. 1987. T.296. C.1406-1409
24. Kopelev N.S., Kiselev Yu.M., Perfiliev Yu.D. Mossbauer spectroscopy of the oxocomplexes iron in higher oxidation states // J. Radioanal. Nucl. Chem. 1992. V.157. R.401-411.
25. "Norms of physiological needs for energy and nutrients for various groups of the population of the Russian Federation" MR 2.3.1.2432-08

Sources (to the History section)

• G. G. Giorgadze."Text of Anitta" and some questions of the early history of the Hittites
• R. M. Abramishvili. On the issue of the development of iron in the territory of Eastern Georgia, VGMG, XXII-B, 1961.
• Khakhutayshvili D. A. On the history of ancient Colchian iron metallurgy. Questions of ancient history (Caucasian-Middle Eastern collection, issue 4). Tbilisi, 1973.
• Herodotus."History", 1:28.
• Homer. Iliad, Odyssey.
• Virgil."Aeneid", 3:105.
• Aristotle."On Incredible Rumors", II, 48. VDI, 1947, No. 2, p. 327.
• Lomonosov M.V. The first foundations of metallurgy.

see also

• Category: Iron compounds

Links

• Diseases caused by deficiency and excess of iron in the human body

Periodic system of chemical elements of D. I. Mendeleev
																						Fe

Iron in its pure form is a gray ductile metal that is easily machined. And yet, for humans, the Fe element is more practical in combination with carbon and other impurities that allow the formation of metal alloys - steels and cast irons. 95% - that is how much of all metal products produced on the planet contain iron as the main element.

Iron: history

The first iron products made by man are dated by scientists to the 4th millennium BC. e., and studies have shown that meteoric iron was used for their production, which is characterized by a 5-30% nickel content. Interestingly, until mankind mastered the extraction of Fe by smelting it, iron was valued more than gold. This was explained by the fact that stronger and more reliable steel was much more suitable for the manufacture of tools and weapons than copper and bronze.

The ancient Romans learned how to make the first cast iron: their furnaces could raise the temperature of the ore to 1400 ° C, while 1100-1200 ° C was enough for cast iron. Subsequently, they also received pure steel, the melting point of which, as you know, is 1535 degrees Celsius. Celsius.

Chemical properties of Fe

What does iron interact with? Iron interacts with oxygen, which is accompanied by the formation of oxides; with water in the presence of oxygen; with sulfuric and hydrochloric acids:

• 3Fe + 2O 2 \u003d Fe 3 O 4
• 4Fe + 3O 2 + 6H 2 O \u003d 4Fe (OH) 3
• Fe + H 2 SO 4 \u003d FeSO 4 + H 2
• Fe + 2HCl \u003d FeCl 2 + H 2

Also, iron reacts to alkalis only if they are melts of strong oxidizing agents. Iron does not react with oxidizing agents at ordinary temperature, but always begins to react when it is raised.

The use of iron in construction

The use of iron by the construction industry today cannot be overestimated, because metal structures are the basis of absolutely any modern structure. In this area, Fe is used in the composition of conventional steels, cast iron and wrought iron. This element is everywhere, from critical structures to anchor bolts and nails.

The construction of building structures made of steel is much cheaper, besides, here we can talk about higher rates of construction. This markedly increases the use of iron in construction, while the industry itself masters the use of new, more efficient and reliable alloys based on Fe.

The use of iron in industry

The use of iron and its alloys - cast iron and steel - is the basis of modern machine, machine tool, aircraft, instrument making and the manufacture of other equipment. Thanks to cyanides and Fe oxides, the paint and varnish industry functions, iron sulfates are used in water treatment. Heavy industry is completely unthinkable without the use of alloys based on Fe + C. In a word, iron is an indispensable, but at the same time accessible and relatively inexpensive metal, which in the composition of alloys has an almost unlimited scope.

The use of iron in medicine

It is known that each adult contains up to 4 grams of iron. This element is extremely important for the functioning of the body, in particular, for the health of the circulatory system (hemoglobin in red blood cells). There are many iron-based drugs that allow you to increase the content of Fe in order to avoid the development of iron deficiency anemia.

Iron- metal, the use of which in industry and everyday life has practically no boundaries. The share of iron in the world production of metals is about 95%. Its use, like any other material, is due to certain properties.

Iron has played a huge role in the development of human civilization. Primitive man began to use iron tools several millennia BC. Then, the only source of this metal were meteorites that fell to Earth, which contained fairly pure iron. This gave rise to legends among many peoples about the heavenly origin of iron.

In the middle of the II millennium BC. In Egypt, the extraction of iron from iron ores was mastered. It is believed that this marked the beginning of the Iron Age in the history of mankind, which replaced the Stone and Bronze Ages. However, already 3-4 thousand years ago, the inhabitants of the Northern Black Sea region - the Cimmerians - smelted iron from swamp ore.

Iron has not lost its significance to this day. It is the most important metal of modern technology. Due to its low strength, iron is practically not used in its pure form. However, in everyday life, steel or cast iron products are often called "iron". After all, important structural materials - steels and cast irons - are alloys of iron with carbon. They make a wide variety of items.

The octagonal pedestal of the monument to Prince Vladimir is built of brick and lined with cast iron.

The prototype of the gigantic structure of the Atomium in Brussels was the model of the crystal lattice of iron. After the reconstruction, the Atomium is again open to the public. The original cover of each ball with an area of ​​240 m 2 was made of 720 triangular aluminum plates. Now they have been replaced by 48 stainless steel plates.

In addition, iron can be a component of alloys based on other metals, such as nickel. Magnetic alloys also contain iron.

Iron-based materials are created that can withstand high and low temperatures, vacuum and high pressures. They successfully resist aggressive environments, alternating voltage, radioactive radiation, etc.

The production of iron and its alloys is constantly growing. These materials are universal, technologically advanced, available and in bulk - cheap. The raw material base of iron is quite large. Already explored reserves of iron ore will last at least two centuries. Therefore, iron will long remain the "foundation" of civilization.

Iron has long been used as an artistic material in Egypt, Mesopotamia, and India. Since the Middle Ages, numerous highly artistic items made of iron alloys have been preserved. Modern artists also widely use iron alloys. material from the site

Among the many artistic products, one cannot leave out of sight the "Mertsalov's Palm" - a work of art by Ukrainian masters. It was forged by Aleksey Mertsalov at the Yuzovsky Metallurgical Plant in 1886. She was recognized as worthy of the Grand Prix of the All-Russian Industrial and Art Exhibition in Nizhny Novgorod. In 1900, Mertsalov's Palm, as part of the exposition of the Yuzovsky Plant, received the highest award at the World Exhibition in Paris.

And in the XXI century. it is difficult to find an industry where iron is not used. Its importance has not diminished with the transition of many metal functions to synthetic materials created by the chemical industry.

Lesson Objectives:

• to form an idea of ​​the physical and chemical properties of iron, depending on the degree of oxidation it exhibits and the nature of the oxidizing agent;
• develop the theoretical thinking of students and their ability to predict the properties of matter, based on knowledge of its structure;
• develop conceptual thinking of such operations as analysis, comparison, generalization, systematization;
• develop such qualities of thinking as objectivity, conciseness and clarity, self-control and activity.

Lesson objectives:

• update students' knowledge on the topic: "The structure of the atom";
• organize the collective work of students from setting a learning task to the final result (draw up a reference diagram for the lesson);
• summarize the material on the topic: “Metals” and consider the properties of iron and its application;
• organize independent research work in pairs to study the chemical properties of iron;
• organize mutual control of students in the classroom.

Lesson type: learning new material.

Reagents and equipment:

• iron (powder, plate, paper clip),
• sulfur,
• hydrochloric acid,
• copper(II) sulfate,
• iron crystal lattice,
• game posters,
• magnet,
• a selection of illustrations on the topic,
• test tubes,
• spirit lamp,
• matches,
• spoon for burning combustible substances,
• geographic Maps.

Lesson structure

1. Introductory part.
2. Learning new material.
3. Homework message.
4. Consolidation of the studied material.

During the classes

1. Introduction

Organizing time.

Checking for students.

The topic of the lesson. Write the topic on the board and in students' notebooks.

2. Learning new material

What do you think the topic of our lesson today will be?

1. The appearance of iron in human civilization marked the beginning of the Iron Age.

Where did the ancient people get iron at a time when they still did not know how to extract it from ore? Iron, translated from the Sumerian language, is a metal “dropped from the sky, heavenly”. The first iron that mankind encountered was iron from meteorites. He proved for the first time that “iron stones fall from the sky”, in 1775 the Russian scientist P.S. Palace, who brought to St. Petersburg a block of native iron meteorite weighing 600 kg. The largest iron meteorite is the Goba meteorite, found in 1920 in Southwest Africa, weighing about 60 tons. Let us recall the tomb of Tutankhamun: gold, gold. Magnificent work delights, brilliance blinds the eyes. But here is what K. Kerram writes in the book “Gods, Tombs, Scholars” about the small iron amulet of Tutankhamen: the greatest value from the point of view of the history of culture”. Only a few iron items were found in the tomb of the pharaoh, among them an iron amulet of the god Horus, a small dagger with an iron blade and a golden handle, a small iron bench “Urs”.

Scientists suggest that it was the countries of Asia Minor, where the Hittite tribes lived, that were the place where ferrous metallurgy appeared. Iron came to Europe from Asia Minor as early as the 1st millennium BC; Thus began the Iron Age in Europe.

The famous damask steel (or damask steel) was made in the East back in the time of Aristotle (4th century BC). But the technology of its manufacture was kept secret for many centuries.

I dreamed of a different sadness
About gray Damascus steel.
I saw the steel temper
As one of the young slaves
Chose, fed him,
So that the flesh of his strength was recruited.
Waiting for the due date
And then a hot blade
Immersed in muscular flesh
They took out the finished blade.
Stronger than steel, did not see the East,
Stronger than steel and bitterer than sorrow.

Since damask steel is a steel with very high hardness and elasticity, products made from it have the ability not to blunt when sharply sharpened. The Russian metallurgist P.P. revealed the secret of damask steel. Anosov. He very slowly cooled hot steel in a special solution of technical oil heated to a certain temperature; during the cooling process, the steel was forged.

(Demonstration of drawings.)

Iron - silver gray metal	Iron - silver gray metal
These nails are made of iron	Steel is used in the automotive industry
Steel is used to make medical instruments	Steel is used to make locomotives
	All metals are susceptible to corrosion
All metals are susceptible to corrosion

2. The position of iron in PSCHEM.

We find out the position of iron in the PSCM, the charge of the nucleus and the distribution of electrons in the atom.

3. Physical properties of iron.

What physical properties of iron do you know?

Iron is a silvery-white metal with a melting point of 1539 o C. It is very ductile, therefore it is easily processed, forged, rolled, stamped. Iron has the ability to be magnetized and demagnetized, therefore it is used as the cores of electromagnets in various electrical machines and apparatuses. It can be given greater strength and hardness by methods of thermal and mechanical action, for example, by quenching and rolling.

There are chemically pure and technically pure iron. Technically pure iron, in fact, is a low-carbon steel, it contains 0.02 -0.04% carbon, and even less oxygen, sulfur, nitrogen and phosphorus. Chemically pure iron contains less than 0.01% impurities. chemically pure iron silvery-gray, shiny, in appearance very similar to platinum metal. Chemically pure iron is resistant to corrosion (remember what is corrosion? Demonstration of a corrosive nail) and well resists the action of acids. However, insignificant fractions of impurities deprive it of these precious properties.

4. Chemical properties of iron.

Based on the knowledge about the chemical properties of metals, what do you think the chemical properties of iron will be?

Demonstration of experiences.

• The interaction of iron with sulfur.

Practical work.

• The interaction of iron with hydrochloric acid.
• Interaction of iron with copper (II) sulfate.

5. The use of iron.

Conversation on:

- How do you think up, what is the distribution of iron in nature?

Iron is one of the most common elements in nature. In the earth's crust, its mass fraction is 5.1%, according to this indicator, it is second only to oxygen, silicon and aluminum. A lot of iron is also found in celestial bodies, which is established from the data of spectral analysis. In samples of lunar soil, which were delivered by the automatic station "Luna", iron was found in an unoxidized state.

Iron ores are quite widespread on Earth. The names of the mountains in the Urals speak for themselves: High, Magnetic, Iron. Agricultural chemists find iron compounds in soils.

In what form does iron occur in nature?

Iron is found in most rocks. To obtain iron, iron ores with an iron content of 30-70% or more are used. The main iron ores are: magnetite - Fe 3 O 4 contains 72% iron, deposits are found in the South Urals, the Kursk magnetic anomaly; hematite - Fe 2 O 3 contains up to 65% iron, such deposits are found in the Krivoy Rog region; limonite - Fe 2 O 3 * nH 2 O contains up to 60% iron, deposits are found in the Crimea; pyrite - FeS 2 contains approximately 47% iron, deposits are found in the Urals. (Working with contour maps).

What is the role of iron in human and plant life?

Biochemists have discovered the important role of iron in the life of plants, animals and humans. Being part of an extremely complex organic compound called hemoglobin, iron determines the red color of this substance, which in turn determines the color of the blood of humans and animals. The body of an adult contains 3 g of pure iron, 75% of which is part of hemoglobin. The main role of hemoglobin is the transfer of oxygen from the lungs to the tissues, and in the opposite direction - CO 2.

Plants also need iron. It is part of the cytoplasm, participates in the process of photosynthesis. Plants grown on an iron-free substrate have white leaves. A small addition of iron to the substrate - and they turn green. Moreover, it is worth smearing a white sheet with a solution of salt containing iron, and soon the smeared place turns green.

So from the same reason - the presence of iron in juices and tissues - the leaves of plants turn green cheerfully and the cheeks of a person blush brightly.

Approximately 90% of the metals used by mankind are iron-based alloys. There is a lot of iron smelted in the world, about 50 times more than aluminum, not to mention other metals. Iron-based alloys are universal, technologically advanced, affordable, and cheap. Iron has long to be the foundation of civilization.

3. Post home stuff

14, ex. No. 6, 8, 9 (according to the workbook for the textbook by O.S Gabrielyan “Chemistry 9”, 2003).

4. Consolidation of the studied material

1. Using the reference diagram written on the blackboard, conclude: what is iron and what are its properties?
2. Graphic dictation (prepare in advance leaflets with a drawn straight line, divided into 8 segments and numbered according to the questions of the dictation. Mark with a hut “^” on the segment the number of the position that is considered correct).

Option 1.

1. Iron is an active alkali metal.
2. Iron is easily forged.
3. Iron is part of the bronze alloy.
4. The outer energy level of an iron atom has 2 electrons.
5. Iron interacts with dilute acids.
6. With halogens it forms halides with an oxidation state of +2.
7. Iron does not interact with oxygen.
8. Iron can be obtained by electrolysis of its salt melt.

1	2	3	4	5	6	7	8

Option 2.

1. Iron is a silver-white metal.
2. Iron does not have the ability to be magnetized.
3. Iron atoms exhibit oxidizing properties.
4. The outer energy level of an iron atom has 1 electron.
5. Iron displaces copper from solutions of its salts.
6. With halogens, it forms compounds with an oxidation state of +3.
7. With a solution of sulfuric acid forms iron sulfate (III).
8. Iron does not corrode.

1	2	3	4	5	6	7	8

After completing the assignment, students change their work and check it (the answers to the work are posted on the board, or show through the projector).

Mark criteria:

• "5" - 0 errors,
• “4” - 1-2 errors,
• "3" - 3-4 errors,
• "2" - 5 or more errors.

Used Books

1. Gabrielyan O.S. Chemistry grade 9. – M.: Bustard, 2001.
2. Gabrielyan O.S. The book for the teacher. – M.: Bustard, 2002.
3. Gabrielyan O.S. Chemistry grade 9. Workbook. – M.: Bustard, 2003.
4. Education industry. Digest of articles. Issue 3. - M .: MGIU, 2002.
5. Malyshkina V. Entertaining chemistry. - St. Petersburg, "Trigon", 2001.
6. Program-methodical materials. Chemistry 8-11 grades. – M.: Bustard, 2001.
7. Stepin B.D., Alikberova L.Yu. Chemistry book for home reading. – M.: Chemistry, 1995.
8. I'm going to chemistry class. The book for the teacher. – M.: “First of September”, 2000.

Applications

Do you know that?

Iron is one of the most important elements of life. Blood contains iron, and it is iron that determines the color of blood, as well as its main property - the ability to bind and release oxygen. This ability is possessed by a complex compound - heme - an integral part of the hemoglobin molecule. In addition to hemoglobin, iron in our body is also in myoglobin, a protein that stores oxygen in the muscles. There are also iron-containing enzymes.

Near the city of Delhi in India, there is an iron column without the slightest speck of rust, although its age is almost 2800 years. This is the famous Kutub column, about seven meters high and weighing 6.5 tons. The inscription on the column says that it was erected in the 9th century. BC e. The rusting of iron - the formation of iron metahydroxide - is associated with its interaction with moisture and atmospheric oxygen.

However, this reaction, in the absence of various impurities in iron, and primarily carbon, silicon and sulfur, does not proceed. The column was made of very pure metal: iron in the column turned out to be 99.72%. This explains its durability and corrosion resistance.

In 1934, an article appeared in the "Mining Journal" "Improvement of iron and steel by ... rusting in the ground." The method of turning iron into steel through rusting in the earth has been known to people since ancient times. For example, the Circassians in the Caucasus buried strip iron in the ground, and after digging it out after 10-15 years, they forged their sabers from it, which could even cut through a gun barrel, shield, and bones of the enemy.

Hematite

Hematite, or red iron ore - the main ore of the main metal of our time - iron. The iron content in it reaches 70%. Hematite has been known for a long time. In Babylon and Ancient Egypt, it was used in jewelry, for the manufacture of seals, along with chalcedony served as a favorite material as a carved stone. Alexander the Great had a ring inlaid with hematite, which he believed made him invulnerable in battle. In antiquity and in the Middle Ages, hematite was known as a blood-stopping medicine. Powder from this mineral has been used for gold and silver products since ancient times.

The name of the mineral comes from the Greek deta- blood, which is associated with the cherry or wax-red color of the powder of this mineral.

An important feature of the mineral is the ability to retain color and transfer it to other minerals, which get even a small admixture of hematite. The pink color of the granite columns of St. Isaac's Cathedral is the color of feldspars, which in turn are painted with finely powdered hematite. The picturesque patterns of jasper used in the decoration of the metro stations of the capital, the orange and pink cornelians of the Crimea, the coral-red interlayers of sylvin and carnallite in the salt strata - all owe their color to hematite.

Red paint has long been made from hematite. All famous frescoes made 15-20 thousand years ago - the wonderful bison of the Altamira cave and mammoths from the famous Cape cave - are made with both brown oxides and iron hydroxides.

Magnetite

Magnetite, or magnetic iron ore - a mineral containing 72% iron. It is the richest iron ore. The remarkable thing about this mineral is its natural magnetism - the property due to which it was discovered.

According to the Roman scientist Pliny, magnetite is named after the Greek shepherd Magnes. Magnes grazed the herd near the hill above the river. Hindu in Thessaly. Suddenly, a staff with an iron tip and sandals lined with nails were attracted to itself by a mountain composed of solid gray stone. The mineral magnetite, in turn, gave the name to the magnet, the magnetic field and the whole mysterious phenomenon of magnetism, which has been closely studied since the time of Aristotle to this day.

The magnetic properties of this mineral are still used today, primarily to search for deposits. This is how unique iron deposits were discovered in the area of ​​the Kursk Magnetic Anomaly (KMA). The mineral is heavy: an apple-sized sample of magnetite weighs 1.5 kg.

In ancient times, magnetite was endowed with all sorts of healing properties and the ability to work miracles. It was used to extract metal from wounds, and Ivan the Terrible among his treasures, along with other stones, kept his unremarkable crystals.

Pyrite is a mineral similar to fire.

Pyrite - one of those minerals, seeing which you want to exclaim: "Is it really so?" It is hard to believe that the highest class of cutting and polishing that strikes us in man-made products, in pyrite crystals, is a generous gift of nature.

Pyrite got its name from the Greek word "pyros" - fire, which is associated with its property to spark when struck by steel objects. This beautiful mineral strikes with a golden color, a bright sheen on almost always clear edges. Due to its properties, pyrite has been known since ancient times, and during epidemics of the gold rush, pyrite sparkles in a quartz vein turned more than one hot head. Even now, novice stone lovers often mistake pyrite for gold.

Pyrite is an omnipresent mineral: it is formed from magma, from vapors and solutions, and even from sediments, each time in specific forms and combinations. A case is known when, over several decades, the body of a miner who fell into a mine turned into pyrite. There is a lot of iron in pyrite - 46.5%, but it is expensive and unprofitable to extract it.