What does iron taste like chemistry. The use of iron: from foundation reinforcement to a magnetic drive

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;
• to 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. 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 resists well to 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 board, draw a conclusion: 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.

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.

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 oxygen in the air.

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, into which at least a small admixture of hematite gets. 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.

IRON, Fe, chemical element, atomic weight 55.84, serial number 26; located in the VIII group of the periodic system in the same row with cobalt and nickel, melting point - 1529 ° C, boiling point - 2450 ° C; in the solid state has a bluish-silver color. In free form, iron is found only in meteorites, which, however, contain admixtures of Ni, P, C, and other elements. In nature, iron compounds are widely distributed throughout (soil, minerals, animal hemoglobin, plant chlorophyll), Ch. arr. in the form of oxides, hydrates of oxides and sulfur compounds, as well as iron carbonate, of which most iron ores are composed.

Chemically pure iron is obtained by heating oxalic iron, and at 440 ° C, at first, an opaque powder of ferrous oxide is obtained, which has the ability to ignite in air (the so-called pyrophoric iron); upon subsequent reduction of this oxide, the resulting powder acquires a gray color and loses its pyrophoric properties, turning into metallic iron. During the reduction of ferrous oxide at 700° C., iron precipitates in the form of small crystals, which are then fused in vacuum. Another way to obtain chemically pure iron is the electrolysis of a solution of iron salts, such as FeSO 4 or FeCl 3 mixed with MgSO 4 , CaCl 2 or NH 4 Cl (at temperatures above 100°C). However, at the same time, iron occludes a significant amount of electrolytic hydrogen, as a result of which it acquires hardness. When calcined to 700 ° C, hydrogen is released, and iron becomes soft and is cut with a knife, like lead (hardness on the Mohs scale is 4.5). Very pure iron can be obtained aluminothermally from pure iron oxide. (see Aluminothermy). Well-formed iron crystals are rare. Octahedral crystals sometimes form in the cavities of large pieces of cast iron. A characteristic property of iron is its softening, malleability and ductility at a temperature much lower than the melting point. When strong nitric acid (not containing lower nitrogen oxides) acts on iron, iron becomes covered with a coating of oxides and becomes insoluble in nitric acid.

Iron compounds

Easily combining with oxygen, iron forms several oxides: FeO - ferrous oxide, Fe 2 O 3 - iron oxide, FeO 3 - ferric anhydride and FeO 4 - anhydride of ironic acid. In addition, iron also forms an oxide of the mixed type Fe 3 O 4 - ferrous oxide, the so-called. iron scale. In dry air, however, iron does not oxidize; rust is an aqueous iron oxide formed with the participation of air moisture and CO 2 . Ferrous oxide FeO corresponds to hydrate Fe (OH) 2 and a number of salts of divalent iron, capable of being oxidized into salts of iron oxide, Fe 2 O 3, in which iron manifests itself as a trivalent element; in air, iron oxide hydrate, which has strong reducing properties, is easily oxidized, turning into iron oxide hydrate. Ferrous oxide hydrate is slightly soluble in water, and this solution has a clearly alkaline reaction, indicating the basic character of ferrous iron. Iron oxide is found in nature (see. Iron minium), while artificially m. obtained in the form of a red powder by calcining iron powder and by burning sulfur pyrites to obtain sulfur dioxide. Anhydrous iron oxide, Fe 2 O 3, m. obtained in two modifications, and the transition from one of them to another occurs when heated and is accompanied by a significant release of heat (self-heating). With strong calcination, Fe 2 O 3 releases oxygen and passes into magnetic oxide, Fe 3 O 4. Under the action of alkalis on solutions of ferric iron salts, a precipitate of hydrate Fe 4 O 9 H 6 (2Fe 2 O 3 3H 2 O) precipitates; when it is boiled with water, Fe 2 O 3 ·H 2 O hydrate is formed, which is difficult to dissolve in acids. Iron forms compounds with various metalloids: with C, P, S, with halides, as well as with metals, for example, with Mn, Cr, W, Cu, etc.

Iron salts are divided into ferrous - ferrous iron (ferro-salt) and oxide - ferric iron (ferri-salt).

ferrous salts . ferric chloride, FeCl 2 , obtained by the action of dry chlorine on iron, in the form of colorless leaves; when iron is dissolved in HCl, ferric chloride is obtained in the form of FeCl 2 4H 2 O hydrate and is used in the form of aqueous or alcoholic solutions in medicine. Iron iodide, FeJ 2 , is obtained from iron and iodine under water in the form of green leaves and is used in medicine (Sirupus ferri jodati); with further action of iodine, FeJ 3 (Liquor ferri sesquijodati) is formed.

ferrous sulfate, ferrous sulfate, FeSO 4 7H 2 O (green crystals) is formed in nature as a result of the oxidation of pyrite and sulfur pyrites; this salt is also formed as a by-product in the production of alum; when weathered or when heated to 300 ° C, it turns into a white anhydrous salt - FeSO 4; also forms hydrates with 5, 4, 3, 2 and 1 water particles; easily soluble in cold water (in hot water up to 300%); the solution is acidic due to hydrolysis; oxidizes in air, especially easily in the presence of another oxidizing substance, for example, oxalic acid salts, which FeSO 4 involves in a coupled oxidation reaction, discolors KMnO 4; the process proceeds according to the following equation:

2KMnO 4 + 10FeSO 4 + 8H 2 SO 4 = 2MnSO 4 + K 2 SO 4 + 5Fe 2 (SO 4) 2 + 8H 2 O.

For this purpose, however, the more permanent double salt of Mohr (NH 4) 2 Fe (SO 4) 2 6H 2 O is used for this purpose. -brown color of the (FeNO) SO 4 complex, as well as for the production of ink (with tannic acids), as a stain for dyeing, for binding malodorous gases (H 2 S, NH 3) in latrines, etc.

Iron ferrous salts are used in photography due to their ability to reduce silver compounds in a latent image imprinted on a photographic plate.

iron carbonate, FeCO 3 , occurs naturally as siderite or iron spar; obtained by precipitation of aqueous solutions of iron ferrous salts with carbonates, iron carbonate easily loses CO 2 and is oxidized in air to Fe 2 O 3.

Iron bicarbonate, H 2 Fe (CO 3) 2, soluble in water and occurs naturally in ferruginous sources, from which, oxidizing, it is released on the surface of the earth in the form of iron oxide hydrate, Fe (OH) 3, turning into brown iron ore.

Phosphate iron, Fe 3 (PO 4) 2 8H 2 O, white precipitate; occurs in nature slightly colored, due to the oxidation of iron, in a blue color, in the form of vivianite.

Iron oxide salts . Ferric chloride, FeCl 3 (Fe 2 Cl 6), is obtained by the action of excess chlorine on iron in the form of hexagonal red plates; ferric chloride dissolves in air; crystallizes from water in the form of FeCl 3 6H 2 O (yellow crystals); solutions are acidic; during dialysis, it is gradually hydrolyzed almost to the end with the formation of a colloidal solution of Fe (OH) 3 hydrate. FeCl 3 dissolves in alcohol and in a mixture of alcohol and ether, when heated, FeCl 3 6H 2 O decomposes into HCl and Fe 2 O 3; used as a dressing and as a hemostatic agent (Liquor ferri sesquichlorati).

Sulphate oxide iron, Fe 2 (SO 4) 3 , yellowish in anhydrous state, highly hydrolyzed in solution; when the solution is heated, basic salts precipitate; ferrous alum, MFe(SO 4) 2 12H 2 O, M - monovalent alkali metal; ammonium alum crystallize best of all, NH 4 Fe (SO 4) 2 12H 2 O.

The oxide FeO 3 is an anhydride of iron acid, as well as the hydrate of this oxide H 2 FeO 4 - ferric acid- in a free state not m. obtained in view of their extreme fragility; but in alkaline solutions there may be salts of iron acid, ferrates (for example, K 2 FeO 4), which are formed by heating iron powder with nitrate or KClO 3. Also known sparingly soluble barium salt of iron acid BaFeO 4 ; thus, ferric acid is in some respects very similar to sulfuric and chromic acids. In 1926, the Kyiv chemist Goralevich described compounds of octavalent iron oxide - supraferrous anhydride FeO 4 obtained by fusing Fe 2 O 3 with saltpeter or Bertolet salt in the form of potassium salt of ironic acid K 2 FeO 5; FeO 4 is a gaseous substance that does not form ironic acid H 2 FeO 5 with water, which, however, can. isolated in the free state by decomposition of salt K 2 FeO 5 with acids. The barium salt BaFeO 5 7H 2 O, as well as the calcium and strontium salts, were obtained by Goralevich in the form of non-decomposing white crystals that release water only at 250-300 ° C and turn green at the same time.

Iron gives compounds: with nitrogen - nitrous iron(nitride) Fe 2 N when iron powder is heated in a jet of NH 3 , with carbon - Fe 3 C carbide when iron is saturated with coal in an electric furnace. In addition, a number of compounds of iron with carbon monoxide have been studied - iron carbonyls, for example, pentacarbonyl Fe(CO) 5 - slightly colored liquid with about 102.9 ° C (at 749 mm, specific gravity 1.4937), then an orange solid Fe 2 (CO) 9, insoluble in ether and chloroform, with specific gravity 2.085.

Of great importance are iron cyanide compounds. In addition to simple cyanides Fe (CN) 2 and Fe (CN) 3, iron forms a number of complex compounds with cyanide salts, such as salts of ferric acid H 4 Fe (CN) 6 and salts of ferric acid H 3 Fe (CN) 6, for example, red blood salt, which, in turn, enter into metabolic decomposition reactions with salts of ferrous and oxide iron, forming blue-colored compounds - Prussian blue and turnbull blue. When replacing one CN group with monovalent groups (NO, NO 2, NH 3, SO 3, CO) in the salts of ferruginous acid H 4 Fe (CN) 6 , prusso salts are formed, for example, sodium nitroprusside (nitroferrous cyanide sodium) Na 2 2H 2 O, obtained by the action of fuming HNO 3 on K 4 Fe (CN) 6, followed by neutralization with soda, in the form of ruby-red crystals, separated by crystallization from the saltpeter formed simultaneously; the corresponding nitroferric-cyanotic acid H 2 also crystallizes as dark red crystals. Sodium nitroprusside is used as a sensitive reagent for hydrogen sulfide and metal sulfides, with which it gives a blood-red, then turning into blue, color. Under the action of copper sulphate on sodium nitroprusside, a pale green precipitate, insoluble in water and alcohol, is formed, which is used to test essential oils.

Analytically, iron is detected by the action on its salts, in an alkaline solution, of the yellow blood salt. Salts of ferric iron form a blue precipitate of Prussian blue. Salts of ferrous iron form a blue precipitate of turnbull blue when exposed to red blood salt. With ammonium thiocyanate NH 4 CNS, ferric iron salts form water-soluble, blood-red colored rhodan iron Fe(CNS) 3 ; with tannin, iron oxide salts form ink. Copper salts of ferric-cyanotic acid are also distinguished by intense coloration, which are used (uvahrom method) in color photography. Of the iron compounds used in medicine, in addition to the mentioned iron halides, the following are important: metallic iron (F. hydrogenio reductum), iron citrate (F. Citricum - 20% Fe), malic iron extract (Extractum ferri pomatum), iron albuminate ( Liquor ferri albuminatum), ferratin is a protein compound with 6% iron; ferratose - a solution of ferratin, carniferrin - a compound of iron with nuclein (30% Fe); ferratogen from yeast nuclein (1% Fe), hematogen - 70% solution of hemoglobin in glycerol, hemol - hemoglobin reduced by zinc dust.

Physical properties of iron

The numerical data available in the literature characterizing the various physical properties of iron fluctuate due to the difficulty of obtaining iron in a chemically pure state. Therefore, the most reliable are the data obtained for electrolytic iron, in which the total content of impurities (C, Si, Mn, S, P) does not exceed 0.01-0.03%. The data below in most cases refer to such hardware. For it, the melting point is 1528°C ± 3°C (Ruer and Klesper, 1914), and the boiling point is ≈ 2450°C. In the solid state, iron exists in four different modifications - α, β, γ and δ, for which the following temperature limits are fairly accurately established:

The transition of iron from one modification to another is detected on the cooling and heating curves by critical points, for which the following designations are accepted:

These critical points are shown in Fig. 1 with schematic heating and cooling curves. The existence of δ-, γ- and α-Fe modifications is currently considered indisputable, while the independent existence of β-Fe is disputed due to the insufficiently sharp difference between its properties and those of α-Fe. All modifications of iron crystallize in the form of a cube, and α, β and δ have a spatial lattice of a centered cube, and γ-Fe - a cube with centered faces. The most distinct crystallographic characteristics of iron modifications are obtained from X-ray spectra, as shown in Fig. 2 (Westgreen, 1929). It follows from the presented X-ray diffraction patterns that for α-, β-, and δ-Fe the lines of the X-ray spectrum are the same; they correspond to the lattice of a centered cube with parameters 2.87, 2.90 and 2.93 Ȧ, and for γ-Fe the spectrum corresponds to the lattice of a cube with centered faces and parameters 3.63-3.68 A.

The specific gravity of iron ranges from 7.855 to 7.864 (Cross and Gill, 1927). When heated, the specific gravity of iron decreases due to thermal expansion, for which the coefficients increase with temperature, as shown in Table. 1 (Driesen, 1914).

The decrease in the expansion coefficients in the ranges of 20–800°C, 20–900°C, 700–800°C, and 800–900°C is explained by anomalies in the expansion upon passing through the critical points A C2 and A C3 . This transition is accompanied by contraction, especially pronounced at point A C3 as shown by the contraction and expansion curves in FIG. 3. The melting of iron is accompanied by its expansion by 4.4% (Gonda and Enda, 1926). The heat capacity of iron is quite significant in comparison with other metals and is expressed for different temperature ranges from 0.11 to 0.20 Cal, as shown in Table. 2 (Obergoffer and Grosse, 1927) and the curve constructed from them (Fig. 4).

In the given data, the transformations A 2 , A 3 , A 4 and the melting of iron are found so clearly that thermal effects are easily calculated for them: A 3 ... + 6.765 Cal, A 4 ... + 2.531 Cal, iron melting ... - 64.38 Cal (according to S. Umino, 1926, - 69.20 Cal).

Iron is characterized by approximately 6-7 times lower thermal conductivity than silver, and 2 times lower than aluminum; namely, the thermal conductivity of iron is at 0°C - 0.2070, at 100°C - 0.1567, at 200°C - 0.1357 and at 275°C - 0.1120 Cal/cm·s·°С. The most characteristic properties of iron are magnetic, expressed by a number of magnetic constants obtained during a complete cycle of iron magnetization. These constants for electrolytic iron are expressed by the following values ​​in gauss (Gumlich, 1909 and 1918):

When passing through point A c2, the ferromagnetic properties of iron almost disappear and can be. detected only with very precise magnetic measurements. In practice, β-, γ-, and δ-modifications are considered non-magnetic. The electrical conductivity for iron at 20°C is R -1 mo m/mm 2 (where R is the electrical resistance of iron, equal to 0.099 Ω mm 2 /m). The temperature coefficient of electrical resistance a0-100 ° x10 5 ranges from 560 to 660, where

Cold working (rolling, forging, broaching, stamping) has a very noticeable effect on the physical properties of iron. So, their % change during cold rolling is expressed by the following figures (Gerens, 1911): coercive voltage + 323%, magnetic hysteresis + 222%, electrical resistance + 2%, specific gravity - 1%, magnetic permeability - 65%. The latter circumstance makes understandable those significant fluctuations in physical properties that are observed by different researchers: the influence of impurities is often accompanied by the influence of cold mechanical treatment.

Very little is known about the mechanical properties of pure iron. Electrolytic iron fused in a void found: tensile strength 25 kg / mm 2, elongation - 60%, cross-sectional compression - 85%, Brinell hardness - from 60 to 70.

The structure of iron depends on the content of impurities in it (even in small quantities) and the pre-treatment of the material. The microstructure of iron, like other pure metals, consists of more or less large grains (crystallites), which are called ferrite here.

The sizes and sharpness of their outlines depend ch. arr. on the iron cooling rate: the lower the latter, the more developed the grains and the sharper their contours. From the surface, the grains are most often unequally colored due to unequal crystallography, their orientation, and the unequal etching action of reagents in different directions in the crystal. It is not uncommon for grains to be elongated in one direction as a result of mechanical processing. If the processing took place at low temperatures, then shear lines (Neumann lines) appear on the surface of the grains as a result of the sliding of individual parts of the crystallites along their cleavage planes. These lines are one of the signs of hardening and those changes in properties that were mentioned above.

Iron in metallurgy

The term iron in modern metallurgy is assigned only to wrought iron, i.e., a low-carbon product obtained in a pasty state at a temperature not sufficient to melt iron, but so high that its individual particles are well welded to each other, giving after forging a homogeneous soft product , not accepting hardening. Iron (in the indicated sense of the word) is obtained: 1) directly from the ore in a paste-like state by a cheese-blowing process; 2) in the same way, but at a lower temperature, insufficient for welding iron particles; 3) redistribution of cast iron by the blooming process; 4) redistribution of cast iron by puddling.

1) Cheese blowing process in present. time is used only by uncultured peoples and in such areas where (due to the lack of convenient means of communication) American or European iron, obtained by modern methods, cannot penetrate. The process is carried out in open raw furnaces and furnaces. The raw materials for it are iron ore (usually brown iron ore) and charcoal. Coal is poured into the hearth in that half of it where the blast is supplied, while the ore is in a heap, from the opposite side. Carbon monoxide formed in a thick layer of burning coal passes through the entire thickness of the ore and, having a high temperature, reduces iron. Ore recovery is carried out gradually - from the surface of individual pieces to the core. Starting at the top of the heap, it accelerates as the ore moves into an area of ​​higher temperature; in this case, iron oxide passes first into magnetic oxide, then into oxide, and, finally, metallic iron appears on the surface of the ore pieces. At the same time, earthy impurities of the ore (waste rock) are combined with iron oxide that has not yet been reduced and form a low-melting ferrous slag, which melts through the cracks of the metal shell, which forms, as it were, a shell in each piece of ore. Being heated to a white-hot heat, these shells are welded to each other, forming a spongy mass of iron at the bottom of the hearth - a kritsu, penetrated by slag. To separate from the latter, the kritsa taken out of the hearth is cut into several parts, each of which is forged, welded, after cooling in the same hearth into strips or directly into products (household items, weapons). In India, the cheese-making process is still carried out in cheese-making furnaces, which differ from furnaces only in a slightly higher height - about 1.5 m. The walls of the furnaces are made of clay mass (not brick) and serve only one smelting. The blast is fed into the furnace through one tuyere by bellows driven by feet or hands. A certain amount of charcoal (“idle head”) is loaded into an empty furnace, and then alternately, in separate layers, ore and coal, with the amount of the first gradually increasing until it reaches a certain relationship to coal; the weight of the whole ore filled is determined by the desired weight of the bloom, which, generally speaking, is negligible. The recovery process is the same as in the forge; iron is also not completely restored, and the resulting bloom contains a lot of ferruginous slag. Kritsu is extracted by breaking the oven and cut into pieces, 2-3 kg in weight. Each of them is heated in a forge and processed under a hammer; the result is an excellent soft iron, which, among other things, is the material for the manufacture of Indian steel "woots" (damask steel). Its composition is as follows (in%):

The negligible content of elements - iron impurities - or their complete absence is explained by the purity of the ore, the incomplete reduction of iron and the low temperature in the furnace. The consumption of charcoal due to the small size of furnaces and furnaces and the frequency of their action is very high. In Finland, Sweden and the Urals, iron was smelted in the Husgavel cheese-blast furnace, in which it was possible to control the process of reduction and saturation of iron with carbon; coal consumption in it - up to 1.1 per unit of iron, the output of which reached 90% of its content in the ore.

2) In the future, it is necessary to expect the development of iron production directly from ore, not by using a raw-blast process, but by reducing iron at a temperature insufficient for the formation of slag and even for sintering waste ore (1000 ° C). The advantages of such a process are the possibility of using low-grade fuels, the elimination of flux and the heat consumption for slag melting.

3) The production of wrought iron by the redistribution of cast iron by the blooming process is carried out in the blooming furnaces of Ch. arr. in Sweden (we have - in the Urals). For redistribution, special cast iron is smelted, the so-called. Lancashire, giving the least waste. It contains: 0.3-0.45% Si, 0.5-0.6% Mn, 0.02 P,<0,01% S. Такой чугун в изломе кажется белым или половинчатым. Горючим в кричных горнах может служить только древесный уголь.

The process is being followed. arr.: the hearth, freed from the cry, but with the ripe slag of the end of the process remaining on the bottom board, is filled with coal, ch. arr. pine, on which cast iron heated by combustion products is laid in the amount of 165-175 kg (for 3/8 m 2 of the cross section of the hearth there are 100 kg of cast iron cages). By turning the valve in the air duct, the blast is directed through the pipes located in the under-roof space of the hearth, and is heated here to a temperature of 150-200 ° C, thus accelerating. melting iron. The melting pig iron is constantly supported (with the help of crowbars) on the coal above the tuyeres. During such work, the entire mass of cast iron is subjected to the oxidative action of atmospheric oxygen and carbon dioxide, passing through the combustion zone in the form of droplets. Their large surface contributes to the rapid oxidation of iron and its impurities - silicon, manganese and carbon. Depending on the content of these impurities, cast iron loses them to a greater or lesser extent before it collects at the bottom of the hearth. Since low-silicon and low-manganese cast iron is reworked in the Swedish forge, then, passing the tuyere horizon, it loses all its Si and Mn (the oxides of which form the main slag with ferrous oxide) and a significant part of the carbon. Cast iron melting lasts 20-25 minutes. At the end of this process, cold blast is put into the furnace. The metal that has settled to the bottom of the hearth begins to react with the ripe slags located there, which contain a large excess (compared to the amount of silica) of iron oxides - Fe 3 O 4 and FeO, which oxidize carbon with the release of carbon monoxide, which boils the entire metal. When the metal thickens (from the loss of carbon) and "sits down as a commodity", the latter is lifted with crowbars above the tuyeres, hot blast is again started and the "commodity" is melted.

During the secondary melting, the metal is oxidized by the oxygen of both the blast and the slags that are melted out of it. At the bottom of the forge, after the first rise, metal falls, soft enough to collect kritsu from some of the most ripe parts of it. But before, when using silicon grades of cast iron, it was necessary to resort to a second and even third rise in goods, which, of course, reduced the productivity of the furnace, increased fuel consumption and iron waste. The results of the work were influenced by the distance of the lances from the bottom board (the depth of the hearth) and the slope of the lances: the steeper the tuyere is set and the smaller the depth of the hearth, the greater the effect of the oxidizing atmosphere on the metal. The more gentle slope of the lances, as well as the greater depth of the hearth, reduces the direct action of the blast oxygen, thus giving a greater role to the action of the slag on the iron impurities; oxidation by them is slower, but without iron fumes. Under any given conditions, the most advantageous position of the lances relative to the bottom board is determined by experience; in a modern swedish forge, the eye of the lance is set at a distance of 220 mm from the bottom board, and the inclination of the tuyeres varies within close limits - from 11 to 12°.

The crack obtained at the bottom of the hearth contains, in contrast to the raw blow, very little mechanically entrained slag; as for the chemical impurities of iron, then Si, Mn and C can be. are completely removed (the negligible content of Si and Mn indicated by the analyzes is part of the mechanical impurity - slag), and sulfur is only partially oxidized by blast during melting. At the same time, phosphorus is also oxidized, leaving in the slag in the form of phosphorus-iron salt, but the latter is then reduced by carbon, and the final metal can contain even relatively more phosphorus (from iron fumes) than the original cast iron. That is why, in order to obtain first-class metal for export in Sweden, exclusively pure pig iron in relation to P is taken into the redistribution. The finished kritsa taken out of the forge is cut into three parts (each 50-55 kg) and compressed under a hammer, giving the appearance of a parallelepiped.

The duration of the redistribution process in the Swedish bloomery is from 65 to 80 minutes; from 2.5 to 3.5 tons of compressed pieces “for fire” are obtained per day, with a consumption of charcoal of only 0.32-0.40 per unit of finished material and its output from 89 to 93.5% of the cast iron specified in the redistribution. Most recently, successful experiments have been made in Sweden in the conversion of liquid iron taken from blast furnaces, and in accelerating the boiling process by stirring the metal with a mechanical rake; while waste decreased to 7%, and coal consumption - to 0.25.

The following data (in%) give the concept of the chemical composition of Swedish and South Ural iron:

Of all the types of iron obtained by industrial methods, Swedish bloomery is the closest to chemically pure and is used instead of the latter in laboratory practice and research work. It differs from raw iron in its uniformity, and from the softest open-hearth metal (cast iron) in the absence of manganese; it is characterized by the highest degree of weldability, ductility and malleability. Swedish bloomery iron exhibits negligible tensile strength of only about 30 kg/mm ​​2 , with an elongation of 40% and a reduction in cross-section of 75%. At present, the annual production of bloomery iron in Sweden has fallen to 50,000 tons, since after the war of 1914-18. the scope of industrial applications for this iron has been greatly reduced. The largest amount of it is used in the manufacture (in England, main arr. and in Germany) of the highest grades of tool and special steels; in Sweden itself, it is used to make special wire (“flower”), horseshoe nails, well forged in a cold state, chains and strip blanks for welded pipes. For the last two purposes, the properties of bloomery iron are especially important: reliable weldability, and for pipes, moreover, the highest resistance to rusting.

4) The development of iron production by the blooming process entailed the destruction of forests; after the latter were taken under the protection of a law in various countries, which limited their felling to an annual increase, Sweden, and then Russia - wooded countries abounding in high quality ores - became the main suppliers of iron on the international market throughout the 18th century. In 1784, the Englishman Cort invented puddling - the process of redistribution of cast iron on the hearth of a fiery furnace, in the furnace of which coal was burned. After Cort's death, Rogers and Gall introduced significant improvements in the design of the puddling furnace, which contributed to the rapid spread of puddling in all industrial countries and completely changed the nature and extent of their iron production during the first half of the 19th century. By this process, they obtained the mass of metal that was needed for the construction of iron ships, railways, locomotives, steam boilers and cars.

The fuel for puddling is long-flame bituminous coal, but where it is not available, we had to resort to brown coal, and here in the Urals - to firewood. Pine wood gives a longer flame than hard coal; it heats well, but the moisture content in the wood should not exceed 12%. Subsequently, the Siemens regenerative oven was used for puddling in the Urals. Finally, in the USA and in our country (in the Volga and Kama basins) puddling furnaces operated on oil sprayed directly into the working space of the furnace.

For speed of redistribution and reduction of fuel consumption, it is desirable to have cold puddling cast iron; when smelting it on coke, however, a lot of sulfur is obtained in the product (0.2 and even 0.3%), and with a high content of phosphorus in the ore, phosphorus. For ordinary commercial grades of iron, such pig iron with a low silicon content (less than 1%), called pig iron, was previously smelted in large quantities. Charcoal cast iron, which was reworked in the Urals and in central Russia, did not contain sulfur and gave a product that was also used for the manufacture of roofing iron. At present, puddling is used to produce high-quality metal according to special specifications, and therefore not ordinary pig iron is supplied to puddling furnaces, but high-quality, for example, manganese or "hematite" (low phosphorus), or, conversely, high-phosphorus for the production of nut iron. Below is the content (in%) of the main elements in some grades of cast iron used for puddling:

The puddling furnace, at the end of the previous operation, usually has a normal amount of slag on the bottom to work with the next charge. When processing strongly silicon cast iron, a lot of slag remains in the furnace, and it has to be lowered; on the contrary, white cast iron is left “dry” under the furnace, and work has to be started by throwing in the required amount of slag, which is taken from under the hammer (“ripe”, the most rich in magnetic oxide). An iron charge is thrown onto the slag, heated in a cast iron (250-300 kg in ordinary and 500-600 kg in double furnaces); then a fresh portion of fuel is thrown into the furnace, the grate is cleaned, and full draft is installed in the furnace. Within 25-35 min. cast iron melts, undergoing b. or m. a significant change in its composition. Hard cast iron is oxidized by the oxygen of the flame, and iron, manganese and silicon give a double silicate flowing down on the hearth of the furnace; melting cast iron exposes more and more layers of solid cast iron, which also oxidizes and melts. At the end of the melting period, two liquid layers are formed on the hearth - cast iron and slag, on the contact surface of which carbon is oxidized, albeit to a weak degree, by magnetic iron oxide, as evidenced by bubbles of carbon monoxide released from the bath. Depending on the content of silicon and manganese in cast iron, an unequal amount of them remains in the molten metal: in low-silicon charcoal cast iron or white cast iron - coke melting - silicon in most cases burns out completely during melting; sometimes a certain amount of it remains in the metal (0.3-0.25%), as well as manganese. Phosphorus is also oxidized at this time, turning into a phosphoric iron salt. From a decrease in the weight of the metal during the burning out of these impurities, the % carbon content may even increase, although some of it is undoubtedly burned by the oxygen of the flame and slag covering the first portions of the molten metal.

To accelerate the burnout of the remaining amounts of silicon, manganese and carbon, puddling is resorted to, i.e., mixing cast iron with slag using a club with a right-angled end. If the metal is liquid (grey cast iron, highly carbonaceous), then the mixing does not reach the goal, and the bath is first made thick by throwing cold ripe slag into it, or by reducing the thrust, incomplete combustion is set in the furnace, accompanied by a very smoky flame (languishing). After a few minutes, during which continuous stirring is carried out, abundant bubbles of burning carbon monoxide appear on the surface of the bath - a product of the oxidation of cast iron carbon by oxygen of magnetic oxide dissolved in the main ferrous slag. As the process progresses, the oxidation of C intensifies and turns into a violent “boiling” of the entire mass of the metal, which is accompanied by its swelling and such a significant increase in volume that part of the slag overflows through the threshold of the working holes. As C burns out, the melting point of the metal rises, and in order for the boiling to continue, the temperature in the furnace is continuously increased. Boiling completed at a low temperature gives a raw product, i.e., a high-carbon spongy mass of iron, unable to weld; ripe goods “sit down” in a hot oven. The process of oxidation of iron impurities in a puddling furnace begins with the oxygen of the slag, which is an alloy of iron monosilica (Fe 2 SiO 4) with magnetic oxide and iron oxide of variable composition. In English furnaces, the composition of the mixture of oxides is expressed by the formula 5Fe 3 O 4 ·5 FeO; at the end of boiling, the ratio of oxides in the depleted slag is expressed by the formula Fe 3 O 4 5FeO, i.e., 80% of the entire magnetic oxide of the slag takes part in the oxidation process. Oxidation reactions m. b. are represented by the following thermochemical equations:

As can be seen from these equations, the oxidation of Si, P and Mn is accompanied by the release of heat and, therefore, heats the bath, while the oxidation of C during the reduction of Fe 3 O 4 to FeO absorbs heat and therefore requires a high temperature. This explains the order of removal of iron impurities and the fact that carbon burnout ends sooner in a hot furnace. Fe 3 O 4 is not reduced to metal, because this requires a higher temperature than that at which “boiling” occurs.

The shrunken "goods", in order to become well-welded iron, still need to be steamed: the goods are left for several minutes in the oven and from time to time they are turned over with crowbars, and its lower parts are placed on top; under the combined action of the oxygen of the flame and slag, impregnating the entire mass of iron, carbon at this time continues to burn out. As soon as a certain amount of well-welded metal is obtained, screams begin to roll out of it, avoiding excessive oxidation. In total, from 5 to 10 kritz are rolled as the goods ripen (no more than 50 kg each); The crackers are kept (steamed) at the threshold in the area of ​​​​the highest temperature and fed under the hammer for compression, which achieves the separation of slag, and giving them the shape of a piece (section from 10x10 to 15x15 cm), convenient for rolling in rolls. To the place of issued shouts, the following ones move forward by moving forward, until the last one. The duration of the process in the production of the highest quality metal (fibrous iron) from ripe (high-carbon) charcoal cast iron in the Urals was as follows: 1) planting cast iron - 5 minutes, 2) melting - 35 minutes, 3) languishing - 25 minutes, 4) puddling (mixing) - 20 min., 5) steaming the goods - 20 min., 6) knurling and steaming the crackers - 40 minutes, 7) issuing the crackers (10-11 pieces) - 20 minutes; total - 165 min. When working on white cast iron, on ordinary commercial iron, the duration of the process was reduced (in Western Europe) to 100 and even 75 minutes.

As for the results of the work, in different metallurgical regions they varied depending on the type of fuel, the quality of cast iron and the grade of iron produced. The Ural stoves, which worked on wood, gave a yield of usable iron per 1 m 3 of firewood from 0.25 to 0.3 tons; oil consumption per unit of iron is 0.33, coal in European furnaces is from 0.75 to 1.1. The daily output of our large stoves (600 kg of cast iron) when working on dried firewood was 4-5 tons; the output of material suitable for the production of roofing iron was 95-93% of the amount of cast iron supplied to the process. In Europe, the daily productivity of ordinary furnaces (cage 250-300 kg) is about 3.5 tons with a loss of 9%, and for high-quality iron - 2.5 tons with a loss of 11%.

In terms of chemical composition and physical properties, puddling iron is a much worse product than blooming iron, on the one hand, and cast open-hearth iron, on the other. The ordinary grades of iron that were previously produced in Western Europe contained a lot of sulfur and phosphorus, since they were produced from impure coke irons, and both of these harmful impurities only partly pass into slag; the amount of slag in puddling iron is 3-6%, in high-quality metal it does not exceed 2%. The presence of slag greatly reduces the results of mechanical testing of puddling iron. Below are some data in% characterizing puddling iron - ordinary Western European and good Ural:

A valuable property, for the sake of which the production of puddling iron is now supported, is its excellent weldability, which is sometimes of particular importance from the point of view of safety. Railway specifications Societies require the manufacture of puddling iron coupling devices, rods for transfer switches and bolts. Due to its better resistance to the corrosive action of water, puddling iron is also used for the production of water pipes. Nuts (a phosphorous coarse-grained metal) and high-quality fibrous iron for rivets and chains are also made from it.

The structure of wrought iron, detected under a microscope even at low magnification, is characterized by the presence of black and light components in the photographic image; the former belong to the slag, and the latter to the iron grains or fibers obtained by drawing the metal.

Trade iron

Metallurgical plants produce iron of two main types for the needs of industry: 1) sheet and 2) high-quality.

Sheet iron is currently rolled up to 3 m wide; with a thickness of 1-3 mm, we call it fine-rolled; from 3 mm and above (usually up to 40 mm) - boiler, tank, ship, depending on the purpose, which corresponds to the composition and mechanical properties of the material. The softest is boiler iron; it usually contains 0.10-0.12% C, 0.4-0.5% Mn, P and S - each not more than 0.05%; its temporary resistance to rupture is not b. more than 41 kg / mm 2 (but not less than 34 kg / mm 2), elongation at break - about 28%. Reservoir iron is made more solid and durable; it contains 0.12-0.15% C; 0.5-0.7% Mn and not more than 0.06% of both P and S; tear resistance 41-49 kg/mm ​​2 , elongation 25-28%. The length of the sheets of boiler and reservoir iron is set by order according to the dimensions of the product riveted from the sheets (avoiding unnecessary seams and trimmings), but usually it does not exceed 8 m, as it is limited for thin sheets by their rapid cooling during the rolling process, and for thick sheets - by the weight of the ingot .

Sheet iron less than 1 mm thick is called tinplate; it is used for making tinplate and as a roofing material. For the latter purpose, in the USSR, sheets are rolled with dimensions of 1422x711 mm, weighing 4-5 kg, with a thickness of 0.5-0.625 mm. Roofing iron is produced by factories in packs weighing 82 kg. Abroad, black tin is classified in trade according to special caliber numbers - from 20 to 30 (the normal thickness of German tin is from 0.875 to 0.22 mm, and English - from 1.0 to 0.31 mm). Tin is made from the softest cast iron, containing 0.08-0.10% C, 0.3-0.35% Mn, if it is made from charcoal cast iron (we have it), and 0.4-0.5% Mn, if the starting material is coke pig iron; tear resistance - from 31 to 34 kg / mm 2, elongation - 28-30%. A variety of sheet iron is corrugated (corrugated) iron. It is divided according to the nature of the waves into iron with low and high waves; in the first, the ratio of wave width to depth ranges from 3 to 4, in the second, 1-2. Corrugated iron is made with a thickness of 0.75-2.0 mm and a sheet width of 0.72-0.81 m (with low waves) and 0.4-0.6 m (with high waves). Corrugated iron is used for roofs, walls of light structures, blinds, and with high waves, in addition, it is used for the construction of rafterless ceilings.

Sectional iron is divided into two classes according to the cross-sectional shape: ordinary sectional iron and shaped.

The first class includes round iron (with a diameter of less than 10 mm called wire), square, flat or strip. The latter, in turn, is divided into: the strip itself - from 10 to 200 mm wide and more than 5 mm thick; hoop - the same width, but with a thickness of 5 to 1 mm, indicated by the caliber number (from the 3rd to the 19th normal German and from the 6th to the 20th new English caliber); tire - from 38 to 51 mm wide and up to 22 mm thick; universal - from 200 to 1000 mm wide and at least 6 mm thick (rolled in special rolls - universal). Both tire and hoop iron are produced by factories in slopes, rolled wire - in coils; other grades - in the form of straight (straightened) strips, usually no more than 8 m long (normal - from 4.5 to 6 m), but by special order for concrete structures, strips are cut up to 18 mm long, and sometimes more.

The main types of shaped iron: angular (equilateral and unequal), box-shaped (channel), tee, I-beam (beam), column (square) and zet iron; there are also some other less common types of shaped iron. According to our normal metric assortment, the dimensions of shaped iron are indicated by the profile number (# - the number, see the width of the shelf or the maximum height of the profile). Angular unequal and tee iron have a double number; for example, No. 16/8 means corner with shelves of 16 and 8 cm or tee with a shelf of 16 cm and a tee height of 8 cm. - double tee.

The composition of ordinary weldable sectional iron: 0.12% C, 0.4% Mn, less than 0.05% P and S - each; its tear resistance is 34-40 kg/mm ​​2 ; but round iron for rivets is made from a softer material of composition: less than 0.10% C, 0.25-0.35% Mn, about 0.03% P and S each. Tensile strength 32-35 kg/mm ​​2 and elongation 28-32%. Shaped not weldable, but riveted iron ("building steel") contains: 0.15 - 0.20% C, 0.5% Mn, up to 0.06% P and S - each; its tear resistance is 40-50 kg/mm ​​2 , elongation is 25-20%. For the production of nuts, iron (Thomas) is made, containing about 0.1% C, but from 0.3 to 0.5% P (the larger the nuts, the more P). Abroad, to meet the needs of special rolling mills, a semi-finished product is circulated in trade - a square billet, usually 50 x 50 mm in cross section.

DEFINITION

Iron is the twenty-sixth element of the Periodic Table. Designation - Fe from the Latin "ferrum". Located in the fourth period, VIIIB group. Refers to metals. The nuclear charge is 26.

Iron is the most common metal on the globe after aluminum: it makes up 4% (mass) of the earth's crust. Iron occurs in the form of various compounds: oxides, sulfides, silicates. Iron is found in the free state only in meteorites.

The most important ores of iron include magnetic iron ore Fe 3 O 4 , red iron ore Fe 2 O 3 , brown iron ore 2Fe 2 O 3 ×3H 2 O and spar iron ore FeCO 3 .

Iron is a silvery (Fig. 1) ductile metal. It lends itself well to forging, rolling and other types of machining. The mechanical properties of iron strongly depend on its purity - on the content of even very small amounts of other elements in it.

Rice. 1. Iron. Appearance.

Atomic and molecular weight of iron

Relative molecular weight of a substance(M r) is a number showing how many times the mass of a given molecule is greater than 1/12 of the mass of a carbon atom, and relative atomic mass of an element(A r) - how many times the average mass of atoms of a chemical element is greater than 1/12 of the mass of a carbon atom.

Since in the free state iron exists in the form of monatomic Fe molecules, the values ​​of its atomic and molecular masses are the same. They are equal to 55.847.

Allotropy and allotropic modifications of iron

Iron forms two crystalline modifications: α-iron and γ-iron. The first of them has a cubic body-centered lattice, the second - a cubic face-centered one. α-Iron is thermodynamically stable in two temperature ranges: below 912 o C and from 1394 o C to the melting point. The melting point of iron is 1539 ± 5 o C. Between 912 o C and 1394 o C, γ-iron is stable.

The temperature ranges of stability of α- and γ-iron are due to the nature of the change in the Gibbs energy of both modifications with a change in temperature. At temperatures below 912 o C and above 1394 o C, the Gibbs energy of α-iron is less than the Gibbs energy of γ-iron, and in the range 912 - 1394 o C - more.

Isotopes of iron

It is known that iron can occur in nature in the form of four stable isotopes 54Fe, 56Fe, 57Fe, and 57Fe. Their mass numbers are 54, 56, 57 and 58, respectively. The nucleus of an atom of the iron isotope 54 Fe contains twenty-six protons and twenty-eight neutrons, and the remaining isotopes differ from it only in the number of neutrons.

There are artificial isotopes of iron with mass numbers from 45 to 72, as well as 6 isomeric states of nuclei. The most long-lived among the above isotopes is 60 Fe with a half-life of 2.6 million years.

iron ions

The electronic formula showing the distribution of iron electrons over the orbits is as follows:

1s 2 2s 2 2p 6 3s 2 3p 6 3d 6 4s 2 .

As a result of chemical interaction, iron gives up its valence electrons, i.e. is their donor, and turns into a positively charged ion:

Fe 0 -2e → Fe 2+;

Fe 0 -3e → Fe 3+.

Molecule and atom of iron

In the free state, iron exists in the form of monatomic Fe molecules. Here are some properties that characterize the atom and molecule of iron:

iron alloys

Until the 19th century, iron alloys were mainly known for their alloys with carbon, which received the names of steel and cast iron. However, in the future, new iron-based alloys containing chromium, nickel and other elements were created. At present, iron alloys are divided into carbon steels, cast irons, alloy steels and steels with special properties.

In technology, iron alloys are usually called ferrous metals, and their production is called ferrous metallurgy.

Examples of problem solving

EXAMPLE 1

The first products made of iron and its alloys were found during excavations and date back to about the 4th millennium BC. That is, even the ancient Egyptians and Sumerians used meteorite deposits of this substance to make jewelry and household items, as well as weapons.

Today, various kinds of iron compounds, as well as pure metal, are the most common and used substances. No wonder the 20th century was considered iron. After all, before the advent and widespread use of plastic and related materials, it was this compound that was of decisive importance for humans. What is this element and what substances it forms, we will consider in this article.

Chemical element iron

If we consider the structure of the atom, then first of all we should indicate its location in the periodic system.

1. Ordinal number - 26.
2. The period is the fourth big one.
3. The eighth group, the secondary subgroup.
4. The atomic weight is 55.847.
5. The structure of the outer electron shell is denoted by the formula 3d 6 4s 2 .
6. - Fe.
7. The name is iron, the reading in the formula is "ferrum".
8. In nature, there are four stable isotopes of the element in question with mass numbers 54, 56, 57, 58.

The chemical element iron also has about 20 different isotopes that are not stable. The possible oxidation states that a given atom can exhibit are:

Not only the element itself is important, but also its various compounds and alloys.

Physical Properties

As a simple substance, iron has a pronounced metallicity. That is, it is a silvery-white metal with a gray tint, which has a high degree of ductility and ductility and a high melting and boiling point. If we consider the characteristics in more detail, then:

• melting point - 1539 0 С;
• boiling - 2862 0 С;
• activity - average;
• refractoriness - high;
• exhibits pronounced magnetic properties.

Depending on the conditions and different temperatures, there are several modifications that iron forms. Their physical properties differ from the fact that the crystal lattices differ.

All modifications have different types of structure of crystal lattices, and also differ in magnetic properties.

Chemical properties

As mentioned above, the simple substance iron exhibits medium chemical activity. However, in a finely dispersed state, it is capable of self-ignition in air, and the metal itself burns out in pure oxygen.

The corrosion ability is high, so the alloys of this substance are coated with alloying compounds. Iron is able to interact with:

• acids;
• oxygen (including air);
• gray;
• halogens;
• when heated - with nitrogen, phosphorus, carbon and silicon;
• with salts of less active metals, reducing them to simple substances;
• with sharp water vapor;
• with iron salts in the oxidation state +3.

It is obvious that, showing such activity, the metal is able to form various compounds, diverse and polar in properties. And so it happens. Iron and its compounds are extremely diverse and are used in various branches of science, technology, and industrial human activity.

Distribution in nature

Natural iron compounds are quite common, because it is the second most common element on our planet after aluminum. At the same time, in its pure form, the metal is extremely rare, as part of meteorites, which indicates its large accumulations in space. The main mass is contained in the composition of ores, rocks and minerals.

If we talk about the percentage of the element in question in nature, then the following figures can be given.

1. The cores of the terrestrial planets - 90%.
2. In the earth's crust - 5%.
3. In the Earth's mantle - 12%.
4. In the earth's core - 86%.
5. In river water - 2 mg/l.
6. In the sea and ocean - 0.02 mg / l.

The most common iron compounds form the following minerals:

• magnetite;
• limonite or brown iron ore;
• vivianite;
• pyrrhotite;
• pyrite;
• siderite;
• marcasite;
• lellingite;
• mispikel;
• milanterite and others.

This is still a long list, because there are really a lot of them. In addition, various alloys that are created by man are widespread. These are also such iron compounds, without which it is difficult to imagine the modern life of people. These include two main types:

• cast irons;
• become.

Iron is also a valuable addition to many nickel alloys.

Iron(II) compounds

These include those in which the oxidation state of the forming element is +2. They are quite numerous, because they include:

• oxide;
• hydroxide;
• binary compounds;
• complex salts;
• complex compounds.

The formulas of chemical compounds in which iron exhibits the indicated degree of oxidation are individual for each class. Consider the most important and common of them.

1. Iron(II) oxide. Black powder, insoluble in water. The nature of the connection is basic. It is able to quickly oxidize, however, it can also be easily reduced to a simple substance. It dissolves in acids to form the corresponding salts. Formula - FeO.
2. Iron(II) hydroxide. It is a white amorphous precipitate. Formed by the reaction of salts with bases (alkalis). It shows weak basic properties, is able to quickly oxidize in air to iron compounds +3. Formula - Fe (OH) 2.
3. The salts of an element in the specified oxidation state. They have, as a rule, a pale green color of the solution, oxidize well even in air, acquiring and turning into iron salts 3. Dissolve in water. Examples of compounds: FeCL 2 , FeSO 4 , Fe(NO 3) 2 .

   

   Several compounds are of practical importance among the designated substances. First, (II). This is the main supplier of ions to the human body with anemia. When such an ailment is diagnosed in a patient, he is prescribed complex preparations, which are based on the compound in question. This is how iron deficiency in the body is replenished.

   Secondly, that is, iron (II) sulfate, together with copper, is used to destroy agricultural pests in crops. The method has been proving its effectiveness for more than a dozen years, therefore it is very much appreciated by gardeners and gardeners.

   Mora Salt

   This is a compound that is a crystalline hydrate of iron and ammonium sulfate. Its formula is written as FeSO 4 * (NH 4) 2 SO 4 * 6H 2 O. One of the iron (II) compounds, which has been widely used in practice. The main areas of human use are as follows.

   1. Pharmaceutics.
   2. Scientific research and laboratory titrimetric analyzes (to determine the content of chromium, potassium permanganate, vanadium).
   3. Medicine - as an additive to food with a lack of iron in the patient's body.
   4. For impregnation of wooden products, as Mora salt protects against decay processes.

   There are other areas in which this substance finds application. It got its name in honor of the German chemist who first discovered the manifested properties.

   Substances with an oxidation state of iron (III)

   The properties of iron compounds, in which it exhibits an oxidation state of +3, are somewhat different from those discussed above. Thus, the nature of the corresponding oxide and hydroxide is no longer basic, but pronounced amphoteric. We give a description of the main substances.

   
   

   Among the examples given, from a practical point of view, such a crystalline hydrate as FeCL 3 * 6H 2 O, or iron (III) chloride hexahydrate, is important. It is used in medicine to stop bleeding and replenish iron ions in the body with anemia.

   Iron(III) sulfate pentahydrate is used to purify drinking water, as it behaves as a coagulant.

   Iron(VI) compounds

   The formulas of the chemical compounds of iron, where it exhibits a special oxidation state of +6, can be written as follows:

   • K 2 FeO 4 ;
   • Na 2 FeO 4 ;
   • MgFeO 4 and others.

   All of them have a common name - ferrates - and have similar properties (strong reducing agents). They are also able to disinfect and have a bactericidal effect. This allows them to be used for the treatment of drinking water on an industrial scale.

   Complex compounds

   Special substances are very important in analytical chemistry and not only. Those that form in aqueous solutions of salts. These are complex compounds of iron. The most popular and well-studied of them are as follows.

   1. Potassium hexacyanoferrate (II) K 4 . Another name for the compound is yellow blood salt. It is used for qualitative determination of iron ion Fe 3+ in solution. As a result of exposure, the solution acquires a beautiful bright blue color, since another complex is formed - Prussian blue KFe 3+. Since ancient times it has been used as
   2. Potassium hexacyanoferrate (III) K 3 . Another name is red blood salt. It is used as a qualitative reagent for the determination of iron ions Fe 2+ . As a result, a blue precipitate is formed, which is called Turnbull blue. Also used as a dye for fabric.

   

   Iron in organic matter

   Iron and its compounds, as we have already seen, are of great practical importance in the economic life of man. However, in addition to this, its biological role in the body is no less great, on the contrary.

   There is one very important protein, which includes this element. This is hemoglobin. It is thanks to him that oxygen is transported and uniform and timely gas exchange is carried out. Therefore, the role of iron in the vital process - respiration - is simply enormous.

   

   In total, the human body contains about 4 grams of iron, which must be constantly replenished through the food consumed.

IRON (Ferrum, Fe) - an element of group VIII of the periodic system of D. I. Mendeleev; is part of the respiratory pigments, including hemoglobin, is involved in the process of binding and transporting oxygen to tissues in the body of animals and humans; stimulates the function of hematopoietic organs; It is used as a medicine for anemic and some other pathological conditions. The radioactive isotope 59 Fe is used as a radioactive indicator in a wedge, laboratory researches. Ordinal number 26, at. weight 55.847.

Four stable isotopes of iron have been found in nature, with mass numbers 54 (5.84%), 56 (91.68%), 57 (2.17%), and 58 (0.31%).

Iron is found everywhere, both on the Earth, especially in its core, and in meteorites. The earth's crust contains 4.2 weight percent, or 1.5 atomic percent iron. The content of iron in stony meteorites averages 23%, and sometimes reaches 90% (such meteorites are called iron meteorites). In the form of complex organic compounds, iron is a constituent of plant and animal organisms.

Zh. is a part of many minerals, which are iron oxides (red iron ore - Fe 2 O 3, magnetic iron ore - FeO-Fe 2 O 3, brown iron ore - 2Fe 2 O 3 -3H 2 O), or carbonates (siderite - FeCO 3), or sulfur compounds (iron pyrite, magnetic pyrite), or, finally, silicates (eg, olivine, etc.). Zh. is found in ground waters and waters of various reservoirs. Zh. is contained in sea water in a concentration of 5 10 -6%.

In the technique of zinc, it is used in the form of alloys with other elements that significantly change its properties. Iron alloys with carbon are of the greatest importance.

Physico-chemical properties of iron and its compounds

Pure Zh. - a brilliant white malleable metal with a grayish tint; t° pl 1539 ± 5°, t° boiling approx. 3200°; beats weight 7.874; possesses, in comparison with other pure metals, the highest ferromagnetic properties, i.e., the ability to acquire the properties of a magnet under the influence of an external magnetic field.

Two crystalline modifications of iron are known: alpha and gamma iron. The first, alpha modification, is stable below 911° and above 1392°, the second, gamma modification, in the temperature range from 911° to 1392°. At temperatures above 769°, alpha iron is non-magnetic, and below 769°, it is magnetic. Non-magnetic alpha iron is sometimes called beta iron, and high temperature alpha iron is sometimes called delta iron. Zh. easily interacts with diluted acids (for example, with hydrochloric, sulfuric, acetic) with the release of hydrogen and the formation of the corresponding ferrous salts of Zh., i.e., Fe (II) salts. Zh.'s interaction with highly diluted nitric acid occurs without hydrogen evolution with the formation of the ferrous nitrate salt of Zh. - Fe (NO 3) 2 and nitrogen ammonium salt - NH 4 NO 3. At interaction Zh. with konts. nitric acid forms an oxide salt Zh., i.e., a salt of Fe (III), - Fe (NO 3) 3, and nitrogen oxides are simultaneously released.

In dry air, iron is covered with a thin (3 nm thick) oxide film (Fe 2 O 3), but does not rust. At high temperatures, in the presence of air, iron is oxidized, forming iron scale - a mixture of oxide (FeO) and oxide (Fe 2 O 3) Zh. In the presence of moisture and air, iron corrodes; it oxidizes with the formation of rust, the edge is a mixture of hydrated iron oxides. To protect the iron from rusting, it is covered with a thin layer of other metals (zinc, nickel, chromium, etc.) or with oil paints and varnishes, or the formation of iron on the surface is achieved. thin film of nitrous oxide - Fe 3 O 4 (bluing of steel).

Zh. belongs to the elements with variable valence, and therefore its compounds are able to take part in redox reactions. Compounds of bi-, tri- and hexavalent iron are known.

The most stable are compounds of bi- and trivalent iron. Oxygen compounds Zh. - oxide (FeO) and oxide (Fe 2 O 3) - have basic properties and form salts with to-tami. Hydrates of these oxides Fe(OH) 2 , Fe(OH) 3 are insoluble in water. Salts of ferrous, i.e. divalent, liquid (FeCl 2, FeSO 4, etc.), called Fe (II) salts or ferrosalts, are colorless in the anhydrous state, and in the presence of crystallization water or in the dissolved state they have a bluish green color;, they dissociate with the formation of Fe 2+ ions. The crystalline hydrate of double ammonium sulphate and divalent J. (NH 4) 2 SO 4 -FeSO 4 -6H 2 O is called Mohr's salt. A sensitive reaction to salts of Fe (II) is the formation of a precipitate of turnbull blue - Fe 3 2 with p-rum K 3 Fe (CN) 6 .

Salts of oxide, i.e. trivalent iron or Fe (III), called Fe (III) salts or ferrisols, are colored yellow-brown or red-brown, for example, ferric chloride, which is commercially available in the form of a yellow hygroscopic FeCl crystalline hydrate 3 -6H 2 O. Double sulfate salts of Fe (III), called iron alum, for example, iron-ammonium alum (NH 4) 2 SO 4 Fe 2 (SO 4) 3 24H 2 O. In the solution of Fe salts (III) dissociate with the formation of Fe 3+ ions. Sensitive reactions to Fe (III) salts are: 1) the formation of a precipitate of Prussian blue Fe 4 3 with a solution of K 4 Fe (CN) 6 and 2) the formation of red rhodan iron Fe (CNS) 3 with the addition of thiocyanate salts (NH 4 CNS or KCNs).

Compounds of hexavalent iron are salts of iron to-you (ferrates K2FeO4, BaFeO4). Corresponding to these salts iron to - that (H2FeO4) and its anhydride are unstable and in a free state are not received. Ferrates are strong oxidizing agents, they are unstable and easily decompose with the release of oxygen.

There are a large number of complex compounds of liquid. For example, when potassium cyanide is added to salts of ferrous liquid, potassium cyanide first forms a precipitate of cyanide liquid. Fe (CN) 2, which then, with an excess of KCN, dissolves again to form K 4 Fe (CN) 6 [hexacyano- (II) potassium ferrate, potassium ferricyanide, or potassium ferricyanide]. Another example is K 3 Fe (CN) 6 [potassium hexacyano-(III) ferrate, potassium ferricyanide, or potassium ferrocyanide], etc. Ferrocyanide gives the Fe (CN) 4 - ion in solution, and ferricinide gives the Fe ( CN) 6 3- . Zh., contained in these anions, does not give qualitative reactions to iron ions Fe 3+ and Fe 2+. Zh. easily forms complex compounds with many organic acids, as well as with nitrogenous bases. The formation of colored complex compounds of iron with a, alpha1-dipyridyl or with o-phenanthroline underlies very sensitive methods for detecting and quantifying small amounts of iron. Substances such as heme (see Hemoglobin) of biogenic origin are also complex compounds of iron.

With carbon monoxide, iron gives volatile compounds - carbonyls. Carbonyl Zh. Fe (CO) 5 is called pentacarbonyl Zh. and is used to obtain the most pure, free from any impurities Zh. for the purposes of obtaining chemical. catalysts, as well as for some electrical purposes.

Iron in the human body

The body of an adult contains an average of 4-5 g of Fe, of which approx. 70% is in the composition of hemoglobin, (see), 5-10% - in the composition of myoglobin (see), 20-25% in the form of reserve Zh. and no more than 0.1% - in the blood plasma. A nek-swarm quantity Zh. is a part of various organic compounds intracellularly. OK. 1% Zh. is also part of a number of respiratory enzymes (see Respiratory pigments, Respiratory enzymes, Biological oxidation), which catalyze the processes of respiration in cells and tissues.

Zh., found in a blood plasma, is a transport form Zh., a cut is connected with protein transferrin representing beta-globulins and, possibly, alpha-globulins and albumins. Theoretically, 1.25 micrograms of fat can be associated with 1 mg of protein, i.e., in total, approx. 3 mg Zh. However, in fact, transferrin is saturated with Zh. only by 20-50% (an average of one third). Additional quantity Zh., a cut in certain conditions can contact transferrin, defines the unsaturated iron-binding ability (NZhSS) of blood; total amount Zh., a cut can be connected by transferrin, defines the general iron-binding ability (OZHSS) of blood. In the blood serum, the content of Zh. is determined according to Valkvist (V. Vahlquist) in the modification of Hagberg (V. Hagberg) and E. A. Efimova. The method is based on the fact that iron-protein complexes in blood plasma in an acidic environment dissociate with the release of F. Proteins are precipitated, and in a protein-free filtrate, Fe (III) is converted to Fe (II), which forms a colored soluble complex with o-phenanthroline, the color intensity is horn is proportional to the amount of Zh. in the solution. For determination, 0.3 ml of non-hemolyzed blood serum is taken, the calculation is made according to the calibration curve.

The iron-binding ability of blood serum is determined by A. Schade in the modification of Rath (C. Rath) and Finch (C. Finch). The method is based on the fact that the interaction of beta-globulins and divalent iron produces an orange-red complex. Therefore, when ferrosalts (usually Mohr's salts) are added to the blood serum, the intensity of this color increases, edges sharply stabilize at the saturation point of the protein. By quantity Zh., necessary for saturation of protein, judge NZhSS. This value, summed up with the amount of fluid in the blood serum, reflects OZHSS.

Zh.'s maintenance in a blood plasma is subject to daily fluctuations; it decreases by the second half of the day. Zh.'s concentration in a blood plasma also depends on age: at newborns it is equal to 175 mcg%, at children at the age of 1 year - 73 mcg%; then the concentration of Zh. again increases to 110-115 μg% and does not change significantly until the age of 13. In adults, there are differences in the concentration of Zh. in the blood serum depending on gender: the content of Zh. in men is 120 mcg%, and in women - 80 mcg%. In whole blood, this difference is less pronounced. OZHSS of normal blood serum is 290-380 mcg%. With urine in a person, 60-100 mcg of F is excreted per day.

Deposition of iron in tissues

Zh., which is deposited in the tissues of the body, can be of exogenous and endogenous origin. Exogenous siderosis is observed in some professions as an occupational hazard, in particular among miners employed in the development of red iron ore, and among electric welders. In these cases, Fe (III) oxides (Fe 2 O 3) are deposited in the lungs, sometimes with the formation of siderotic nodules diagnosed by radiography. Histologically, nodules are an accumulation of dust containing iron in the lumen of the alveoli, in desquamated alveolar cells, in the interalveolar septa, and in the adventitia of the bronchi with development around the connective tissue. In electric welders, the amount of fluid deposited in the lungs is usually small; its particles are predominantly less than 1 micron; at miners massive deposits are observed., the amount to-rogo in both lungs can reach 45 g and make 39,6% of the weight of the ashes remaining after combustion of a lung. Pure siderosis of the lungs, for example, in electric welders, is not accompanied by pneumosclerosis and disability; miners, however, usually have sidero-silicosis with the development of pneumosclerosis (see).

Exogenous siderosis of the eyeball is observed when iron fragments, shavings, etc. are introduced into the eye; at the same time, metallic fluid passes into bicarbonate, then into hydrate of fluid oxide and is deposited in the processes of the ciliary body, the epithelium of the anterior chamber, the lens capsule, the episcleral tissue, the retina, and the optic nerve, where it can be detected using the appropriate microchem. reactions. Exogenous local siderosis can be observed around iron fragments that have fallen into tissues during household and combat trauma (fragments of grenades, shells, etc.).

The source of endogenous siderosis in the vast majority of cases is hemoglobin with its extra- and intravascular destruction. One of the end products of hemoglobin breakdown is the iron-containing pigment hemosiderin, which is deposited in organs and tissues. Hemosiderin was discovered in 1834 by I. Müller, but the term "hemosiderin" was proposed by A. Neumann only later, in 1888. Hemosiderin is formed by cleavage of heme. It is a polymer of ferritin (see) [Granik (S. Granick)]. Chemically, hemosiderin is an aggregate of Fe(III) hydroxide, more or less firmly bound to proteins, mucopolysaccharides, and cell lipids. The formation of hemosiderin occurs in cells of both mesenchymal and epithelial nature. These cells

V. V. Serov and V. S. Paukov proposed to call them sideroblasts. Hemosiderin granules are synthesized in siderosomes of sideroblasts. Microscopically, hemosiderin has the appearance of grains from yellowish to golden brown, located mostly inside the cells, but sometimes extracellularly. Hemosiderin granules contain up to 35% Zh.; hemosiderin never forms crystalline forms.

Due to the fact that the source of hemosiderin in most cases is hemoglobin, focal deposits of the latter can be observed anywhere in the human body where hemorrhage has occurred (see Hemosiderosis). In hemosiderosis, SH-ferritin (active sulfhydryl form), which has vasoparalytic properties, is detected in the places of hemosiderin deposition. Especially large deposits of hemosiderin, arising from ferritin due to a violation of cellular metabolism Zh., are observed with hemochromatosis (see); while in the liver the amount of deposited fat often exceeds 20-30 g. Deposits of fat in hemochromatosis, in addition to the liver, are observed in the pancreas, kidneys, myocardium, organs of the reticuloendothelial system, sometimes the mucous glands of the trachea, in the thyroid gland, muscles and epithelium of the tongue etc.

In addition to deposits of hemosiderin, sometimes there is impregnation (ferruginization) of the elastic framework of the lungs, elastic membranes of the vessels of the lung with brown induration, or cerebral vessels in the circumference of the hemorrhage (see Brown compaction of the lungs). There is also a ferruginization of individual muscle fibers in the uterus, nerve cells in the brain in certain mental illnesses (idiocy, early and senile dementia, Pick's atrophy, some hyperkinesis). These formations are impregnated with colloidal iron, and ferruginization can be detected only with the help of special reactions.

To detect ionized iron in tissues, the reaction of formation of turnbull blue according to Tiermann-Schmelzer to detect Fe (II) and the reaction of formation of Prussian blue [Perls method using Fe (III)] are most widely used.

The reaction for the formation of turnbull blue is carried out as follows: the prepared sections are placed for 1-24 hours in 10% ammonium sulfide solution to convert all of the fluid into bivalent sulfuric fluid. Then the sections thoroughly rinsed in distilled water are transferred for 10-20 minutes. in a freshly prepared mixture of equal parts of 20% solution of potassium ferricyanide and 1% solution of hydrochloric acid. Zh. is painted in a bright blue color; kernels can be finished with carmine. Use only glass needles to transfer sections.

According to the method of Perls, the sections are placed for several minutes in a freshly prepared mixture of 1 hour 2% aqueous solution of potassium ferricyanide and 1.5 hours 1% solution of hydrochloric acid; then the sections are rinsed with water and the kernels are stained with carmine. J. is painted blue. SH-ferritin is detected using cadmium sulfate (N. D. Klochkov).

Bibliography: Biochemical research methods in the clinic, ed. A. A. Pokrovsky, p. 440, M., 1969; In e r b about l the island and the p. A. and At t e sh e in A. B. Iron in an animal organism, Alma-Ata, 1967, bibliogr.; Glinka N. L. General chemistry, p. 682, L., 1973; Kassirsky I. A. and Alekseev G. A. Clinical hematology, p. 168, M., 1970, bibliogr.; Levin V.I. Production of radioactive isotopes, p. 149, M., 1972; Mashkovsky M. D. Medicines, part 2, p. 94, Moscow, 1977; Normal hematopoiesis and its regulation, ed. N. A. Fedorova, p. 244, M., 1976; Petrov V. N. and Shcherba M. M. Identification, prevalence and geography of iron deficiency, Klin, medical, t. 20, 1972, bibliogr.; P Ya-bov S. I. and Shostka G. D. Molecular genetic aspects of erythropoiesis, L., 1973, bibliogr.; Shch erb and M. M. Iron deficiency states, L., 197 5; Klinische Hamatologie, hrsg. v. H. Begemann, S. 295, Stuttgart, 1970; Pharmacological basis of therapeutics, ed. by L. S. Goodman a. A. Gilman, L., 1975.

G. E. Vladimirov; G. A. Alekseev (gem.), V. V. Bochkarev (rad.), A. M. Vikhert (stalemate. an.), V. V. Churyukanov (farm.).