Known to people since ancient times: scientists attribute ancient household items made from this material to the 4th millennium BC.

It is impossible to imagine human life without iron. It is believed that iron is used for industrial purposes more often than other metals. The most important structures are made from it. Iron is also found in small quantities in the blood. It is the content of the twenty-sixth element that colors the blood red.

Physical properties of iron

Iron burns in oxygen, forming an oxide:

3Fe + 2O₂ = Fe₃O₄.

When heated, iron can react with nonmetals:

Also at a temperature of 700-900 °C it reacts with water vapor:

3Fe + 4H₂O = Fe₃O₄ + 4H₂.

Iron compounds

As is known, iron oxides have ions with two oxidation states: +2 and + 3. Knowing this is extremely important, because completely different qualitative reactions will be carried out for different elements.

Qualitative reactions to iron

A qualitative reaction is needed so that one can easily determine the presence of ions of one substance in solutions or impurities of another. Let us consider the qualitative reactions of divalent and trivalent iron.

Qualitative reactions to iron (III)

The content of ferric ions in a solution can be determined using alkali. If the result is positive, a base is formed - iron (III) hydroxide Fe(OH)₃.

Iron (III) hydroxide Fe(OH)₃

The resulting substance is insoluble in water and has a brown color. It is the brown precipitate that may indicate the presence of ferric ions in the solution:

FeCl₃ + 3NaOH = Fe(OH)₃↓+ 3NaCl.

Fe(III) ions can also be determined using K₃.

A solution of ferric chloride is mixed with a yellowish solution of blood salt. As a result, you can see a beautiful bluish precipitate, which will indicate that ferric ions are present in the solution. You will find spectacular experiments to study the properties of iron.

Qualitative reactions to iron (II)

Fe²⁺ ions react with red blood salt K₄. If a bluish precipitate forms when salt is added, then these ions are present in the solution.

(so-called meteorite iron, which contains more than 90% Fe). In compounds with oxygen and other elements, it is widely distributed in many minerals and ores. It is the third most abundant element in the earth's crust (5.00%) (after silicon and aluminum); It is believed that the earth's core consists mainly of iron. The main minerals are hematite (red iron ore) Fe 2 O 3; limonite Fe 2 O 3 ·nH 2 O (n = 1 - 4), contained, for example, in bog ore; magnetite (magnetic iron ore) Fe 3 O 4 and siderite FeCO 3 . The most common iron mineral, although not the source of its production, is pyrite (sulfur pyrite, iron pyrite) FeS 2, which is sometimes called fool's gold or cat's gold for its yellow luster, although in reality it often contains small impurities of copper, gold , cobalt and other metals.

PROPERTIES OF IRON
Atomic number	26
Atomic mass	55,847
Isotopes:
stable	54, 56, 57, 58
unstable	52, 53, 55, 59
Melting point, °C	1535
Boiling point, °C	3000
Density, g/cm3	7,87
Hardness (Mohs)	4,0-5,0
Content in the earth's crust, % (mass.)	5,00
Oxidation state:
characteristic	+2, +3
other meanings	+1, +4, +6

Story

Iron (elemental) has been known and used since prehistoric times. The first iron objects were probably made from meteorite iron in the form of amulets, jewelry, and working tools. About 3,500 years ago, man discovered a way to reduce red earth containing iron oxide into metal. Since then, a huge number of different products have been made from iron. It played an important role in the development of the material culture of mankind. Nowadays, iron is mainly (95%) smelted from ores in the form of cast iron and steel and is obtained in relatively small quantities by the reduction of metallized pellets, and pure iron is obtained by the thermal decomposition of its compounds or electrolysis of salts.

Properties

Metallic iron is a greyish-white, shiny, hard, plastic substance. Iron crystallizes in three modifications (α, γ, δ). α-Fe has a body-centered cubic crystal lattice, chemically stable up to 910°C. At 910°C, α-Fe transforms into γ-Fe, which is stable in the range 910-1400°C; γ-Fe crystallizes in a face-centered cubic crystal lattice. At temperatures above 1400°C, δ-Fe is formed with a lattice essentially similar to that of α-Fe. Iron is ferromagnetic; it is easily magnetized, but loses its magnetic properties when the magnetic field is removed. With increasing temperature, the magnetic properties of iron deteriorate and above 769°C it is practically impossible to magnetize (sometimes iron in the range 769-910°C is called -Fe); γ-Fe is not a magnetic material.

Usage

Iron- one of the most serviceable metals in an alloy with carbon (steel, cast iron) - a high-strength basis for structural materials. As a material with magnetic properties, iron is used for the cores of electromagnets and armatures of electric machines, as well as as layers and films on magnetic tapes. Pure iron is a catalyst in chemical processes and a component of medicines in medicine.

Iron as a chemical component of the body

Iron is an essential chemical component of many vertebrates, invertebrates and some plants. It is part of the heme (erythrocyte pigment - red blood cells) hemoglobin in the blood, muscle tissue, bone marrow, liver and spleen. Each hemoglobin molecule contains 4 iron atoms, which are capable of creating a reversible and weak bond with oxygen, forming oxyhemoglobin. Blood containing oxyhemoglobin circulates throughout the body, supplying oxygen to tissues for cellular respiration. Therefore, iron is necessary for respiration and the formation of red blood cells. Myoglobin (or muscle hemoglobin) supplies oxygen to the muscles. The total amount of iron in the human body (average weight 70 kg) is 3-5 g. Of this amount, 65% of Fe is in hemoglobin. 10 to 20 mg of Fe daily is required to support the normal metabolism of the average adult. Red meat, eggs, yolk, carrots, fruits, any wheat and green vegetables mainly provide the body with iron in a normal diet; For anemia associated with a lack of iron in the body, take iron supplements.

Iron as a chemical element

From a chemical point of view, iron is a fairly active metal, exhibiting characteristic oxidation states of +2, +3, less often +1, +4, +6. It combines directly with some elements, with S it forms FeS - iron(III) sulfide, with halogens, except iodine, - iron(III) halides, such as FeCl 3. Easily oxidized; with oxygen produces oxides FeO, Fe 2 O 3, Fe 3 O 4 (FeO + Fe 2 O 3), easily corrodes (rusts). Displaces hydrogen from water vapor at high temperatures. It dissolves in dilute acids (for example, HCl, H 2 SO 4, HNO 3), displacing hydrogen and forming Fe(II) salts (respectively, FeCl 2, FeSO 4, Fe(NO 3) 2). In moderately concentrated H 2 SO 4 and HNO 3, iron dissolves to form Fe(III) salts, and in highly concentrated ones it is passivated and does not react. The passivity of iron is apparently explained by the formation of an iron oxide film on its surface, which, however, is easily destroyed by simple scraping.

Iron corrosion

Rusting of iron (atmospheric corrosion of iron)- this is its oxidation by atmospheric oxygen. The reaction occurs in the presence of salt ions dissolved in water and ions formed during the dissociation of carbonic acid, a product of the interaction of atmospheric carbon dioxide and moisture. As a result, loose red rust or hydrated oxide with the composition Fe 2 O 3 nH 2 O is formed.

Connections

Complex connections

Chemical elements and materials
Chemical elements

Brazhnikova Alla Mikhailovna,

GBOU secondary school No. 332

Nevsky district of St. Petersburg

This manual examines questions on the topic “Iron Chemistry”. In addition to traditional theoretical issues, issues that go beyond the basic level are considered. Contains questions for self-control, which enable students to check their level of mastery of the relevant educational material in preparation for the Unified State Exam.

CHAPTER 1. IRON - A SIMPLE SUBSTANCE.

Structure of the iron atom .

Iron is a d-element, located in a secondary subgroup of group VIII of the periodic table. The most common metal in nature after aluminum It is part of many minerals: brown iron ore (hematite) Fe 2 O 3, magnetic iron ore (magnetite) Fe 3 O 4, pyrite FeS 2.

Electronic structure : 1s 2 2s 2 2p 6 3s 2 3p 6 3d 6 4s 2 .

Valence : II, III, (IV).

Oxidation states: 0, +2, +3, +6 (only in ferrates K 2 FeO 4).

Physical properties.

Iron is a shiny, silvery-white metal, mp. - 1539 0 C.

Receipt.

Pure iron can be obtained by reducing oxides with hydrogen when heated, as well as by electrolysis of solutions of its salts. Blast furnace process - producing iron in the form of alloys with carbon (cast iron and steel):

1) 3Fe 2 O 3 + CO → 2Fe 3 O 4 + CO 2

2) Fe 3 O 4 + CO → 3FeO + CO 2

3) FeO + CO → Fe + CO 2

Chemical properties.

I. Interaction with simple substances - non-metals

1) With chlorine and sulfur (when heated). The stronger oxidizing agent chlorine oxidizes iron to Fe 3+, and the weaker oxidizing agent chlorine oxidizes it to Fe 2+:

2Fe 2 + 3Cl → 2FeCl 3

2) With coal, silicon and phosphorus (at high temperature).

3) In dry air it is oxidized by oxygen, forming scale - a mixture of iron (II) and (III) oxides:

3Fe + 2O 2 → Fe 3 O 4 (FeO Fe 2 O 3)

II. Interaction with complex substances.

1) Corrosion (rusting) of iron occurs in humid air:

4Fe + 3O 2 + 6H 2 O → 4Fe(OH) 3

At high temperatures (700 - 900 0 C) in the absence of oxygen, iron reacts with water vapor, displacing hydrogen from it:

3Fe+ 4H 2 O→ Fe 3 O 4 + 4H 2

2) Displaces hydrogen from dilute hydrochloric and sulfuric acids:

Fe+ 2HCl= FeCl 2 + H 2

Fe + H 2 SO 4 (diluted) = FeSO 4 + H 2

Highly concentrated sulfuric and nitric acids do not react with iron at ordinary temperatures due to its passivation.

With dilute nitric acid, iron is oxidized to Fe 3+, the reduction products of HNO 3 depend on its concentration and temperature:

8Fe + 30HNO 3(ultra dil.) →8Fe(NO 3) 3 + 3NH 4 NO 3 + 9H 2 O

Fe + 4HNO 3(dil.) → Fe(NO 3) 3 + NO + 2H 2 O

Fe + 6HNO 3(conc.) → (temperature) Fe(NO 3) 3 + 3NO 2 + 3H 2 O

3) Reaction with solutions of metal salts located to the right of iron in the electrochemical series of metal voltages:

Fe + CuSO 4 → Fe SO 4 + Cu

CHAPTER2. IRON (II) COMPOUNDS.

Iron oxide(II) .

FeO oxide is a black powder, insoluble in water.

Receipt.

Reduction from iron oxide (III) at 500 0 C by the action of carbon monoxide (II):

Fe 2 O 3 + CO→2FeO+ CO 2

Chemical properties.

Basic oxide, it corresponds to Fe(OH) 2 hydroxide: dissolves in acids, forming iron (II) salts:

FeO+ 2HCl→ FeCl 2 + H 2 O

Iron hydroxide (II).

Iron hydroxide Fe(OH) 2 is a water-insoluble base.

Receipt.

The effect of alkalis on iron salts () without air access:

FeSO 4 + NaOH → Fe(OH) 2 ↓+ Na 2 SO 4

Chemical properties.

Fe(OH)2 hydroxide exhibits basic properties and is highly soluble in mineral acids, forming salts.

Fe(OH) 2 + H 2 SO 4 →FeSO 4 + 2H 2 O

When heated, it decomposes:

Fe(OH) 2 → (temperature) FeO+ H 2 O

Redox properties.

Iron (II) compounds exhibit fairly strong reducing properties and are stable only in an inert atmosphere; in air (slowly) or in an aqueous solution under the action of oxidizing agents (quickly) they transform into iron (III) compounds:

4 Fe(OH) 2 (precipitated)+ O 2 + 2H 2 O→ 4 Fe(OH) 3 ↓

2FeCl 2 + Cl 2 → 2FeCl 3

10FeSO 4 + 2KMnO 4 + 8H 2 SO 4 → 5 Fe 2 (SO 4) 3 + 2MnSO 4 + K 2 SO 4 + 8 H 2 O

Iron (II) compounds can also act as oxidizing agents:

FeO+ CO→ (temperature) Fe+ CO

CHAPTER 3. IRON COMPOUNDS (III).

Iron oxide(III)

Fe 2 O 3 oxide is the most stable natural oxygen-containing iron compound. It is an amphoteric oxide, insoluble in water. It is formed when FeS 2 pyrite is roasted (see 20.4 “Obtaining SO 2”.

Chemical properties.

1) Dissolving in acids, it forms iron (III) salts:

Fe 2 O 3 + 6HCl→ 2FeCl 3 + 3H 2 O

2) When fused with potassium carbonate, it forms potassium ferrite:

Fe 2 O 3 + K 2 CO 3 → (temperature) 2KFeO 2 + CO 2

3) Under the action of reducing agents it acts as an oxidizing agent:

Fe 2 O 3 + 3H 2 → (temperature) 2Fe+ 3H 2 O

Iron hydroxide (III)

Iron hydroxide Fe(OH) 3 is a red-brown substance, insoluble in water.

Receipt.

Fe 2 (SO 4) 3 + 6NaOH → 2Fe(OH) 3 ↓ + 3Na 2 SO 4

Chemical properties.

Fe(OH) 3 hydroxide is a weaker base than iron (II) hydroxide and has weak amphotericity.

1) Dissolves in weak acids:

2Fe(OH) 3 + 3H 2 SO 4 → Fe 2 (SO 4) 3 + 6H 2 O

2) When boiled in a 50% NaOH solution, it forms

Fe(OH) 3 + 3NaOH → Na 3

Iron salts (III).

Subject to strong hydrolysis in aqueous solution:

Fe 3+ + H 2 O ↔ Fe(OH) 2+ + H +

Fe 2 (SO 4) 3 + 2H 2 O ↔ Fe(OH)SO 4 + H 2 SO 4

When exposed to strong reducing agents in an aqueous solution, they exhibit oxidizing properties, turning into iron (II) salts:

2FeCl 3 + 2KI → 2FeCl 2 + I 2 + 2KCl

Fe 2 (SO 4) 3 + Fe → 3 Fe

CHAPTER4. QUALITATIVE REACTIONS.

Qualitative reactions to Fe 2+ and Fe 3+ ions.

1. The reagent for the Fe 2+ ion is potassium hexacyanoferrate (III) (red blood salt), which gives with it an intensely blue precipitate of a mixed salt - potassium iron (II) hexacyanoferrate (III) or Turnbull blue:

FeCl 2 + K 3 → KFe 2+ ↓ + 2KCl

1. The reagent for the Fe 3+ ion is the thiocyanate ion (rodanide ion) CNS -, the interaction of which with iron (III) salts produces a blood-red substance - iron (III) thiocyanate:

FeCl 3 + 3KCNS→ Fe(CNS) 3 + 3KCl

3)Fe 3+ ions can also be detected using potassium hexacyanoferrate (II) (yellow blood salt). In this case, a water-insoluble substance of intense blue color is formed - potassium iron (III) hexacyanoferrate (II) or Prussian blue:

FeCl 3 + K 4 → KFe 3+ ↓ + 3KCl

CHAPTER 5. MEDICAL AND BIOLOGICAL IMPORTANCE OF IRON.

The role of iron in the body.

Iron participates in the formation of hemoglobin in the blood, in the synthesis of thyroid hormones, and in protecting the body from bacteria. It is necessary for the formation of immune protective cells and is required for the “work” of B vitamins.

Iron is part of more than 70 different enzymes, including respiratory ones, which ensure respiration processes in cells and tissues, and participate in the neutralization of foreign substances entering the human body.

Hematopoiesis. Hemoglobin.

Gas exchange in the lungs and tissues.

Iron-deficiency anemia.

Lack of iron in the body leads to diseases such as anemia and anemia.

Iron deficiency anemia (IDA) is a hematological syndrome characterized by impaired hemoglobin synthesis due to iron deficiency and manifested by anemia and sideropenia. The main causes of IDA are blood loss and lack of heme-rich food and drink.

The patient may experience fatigue, shortness of breath and palpitations, especially after physical activity, often dizziness and headaches, noise in the ears, and even fainting is possible. The person becomes irritable, sleep is disturbed, and concentration decreases. Because blood flow to the skin is reduced, increased sensitivity to cold may develop. Symptoms also arise from the gastrointestinal tract - a sharp decrease in appetite, dyspeptic disorders (nausea, changes in the nature and frequency of stool).

Iron is an integral part of vital biological complexes, such as hemoglobin (transport of oxygen and carbon dioxide), myoglobin (storage of oxygen in muscles), cytochromes (enzymes). The adult body contains 4-5 g of iron.

LIST OF REFERENCES USED:

1. K.N. Zelenin, V.P. Sergutin, O.V. Malt “We pass the chemistry exam perfectly.” Elbl-SPb LLC, 2001.
2. K.A. Makarov “Medical chemistry”. Publishing house of St. Petersburg State Medical University of St. Petersburg, 1996.
3. N.L. Glinka "General Chemistry". Leningrad "Chemistry", 1985.
4. V.N. Doronkin, A.G. Berezhnaya, T.V. Sazhneva, V.A. Februaryev “Chemistry. Thematic tests for preparing for the Unified State Exam." Publishing house "Legion", Rostov-on-Don, 2012.

The human body contains about 5 g of iron, most of it (70%) is part of blood hemoglobin.

Physical properties

In its free state, iron is a silvery-white metal with a grayish tint. Pure iron is ductile and has ferromagnetic properties. In practice, iron alloys - cast iron and steel - are usually used.

Fe is the most important and most abundant element of the nine d-metals of the Group VIII subgroup. Together with cobalt and nickel it forms the “iron family”.

When forming compounds with other elements, it often uses 2 or 3 electrons (B = II, III).

Iron, like almost all d-elements of group VIII, does not exhibit a higher valency equal to the group number. Its maximum valency reaches VI and appears extremely rarely.

The most typical compounds are those in which the Fe atoms are in oxidation states +2 and +3.

Methods for obtaining iron

1. Technical iron (alloyed with carbon and other impurities) is obtained by carbothermic reduction of its natural compounds according to the following scheme:

Recovery occurs gradually, in 3 stages:

1) 3Fe 2 O 3 + CO = 2Fe 3 O 4 + CO 2

2) Fe 3 O 4 + CO = 3FeO + CO 2

3) FeO + CO = Fe + CO 2

The cast iron resulting from this process contains more than 2% carbon. Subsequently, cast iron is used to produce steel - iron alloys containing less than 1.5% carbon.

2. Very pure iron is obtained in one of the following ways:

a) decomposition of Fe pentacarbonyl

Fe(CO) 5 = Fe + 5СО

b) reduction of pure FeO with hydrogen

FeO + H 2 = Fe + H 2 O

c) electrolysis of aqueous solutions of Fe +2 salts

FeC 2 O 4 = Fe + 2CO 2

iron(II) oxalate

Chemical properties

Fe is a metal of medium activity and exhibits general properties characteristic of metals.

A unique feature is the ability to “rust” in humid air:

In the absence of moisture with dry air, iron begins to react noticeably only at T > 150°C; upon calcination, “iron scale” Fe 3 O 4 is formed:

3Fe + 2O 2 = Fe 3 O 4

Iron does not dissolve in water in the absence of oxygen. At very high temperatures, Fe reacts with water vapor, displacing hydrogen from water molecules:

3 Fe + 4H 2 O(g) = 4H 2

The mechanism of rusting is electrochemical corrosion. The rust product is presented in a simplified form. In fact, a loose layer of a mixture of oxides and hydroxides of variable composition is formed. Unlike the Al 2 O 3 film, this layer does not protect iron from further destruction.

Types of corrosion

Protecting iron from corrosion

1. Interaction with halogens and sulfur at high temperatures.

2Fe + 3Cl 2 = 2FeCl 3

2Fe + 3F 2 = 2FeF 3

Fe + I 2 = FeI 2

Compounds are formed in which the ionic type of bond predominates.

2. Interaction with phosphorus, carbon, silicon (iron does not directly combine with N2 and H2, but dissolves them).

Fe + P = Fe x P y

Fe + C = Fe x C y

Fe + Si = Fe x Si y

Substances of variable composition are formed, such as berthollides (the covalent nature of the bond predominates in the compounds)

3. Interaction with “non-oxidizing” acids (HCl, H 2 SO 4 dil.)

Fe 0 + 2H + → Fe 2+ + H 2

Since Fe is located in the activity series to the left of hydrogen (E° Fe/Fe 2+ = -0.44 V), it is capable of displacing H 2 from ordinary acids.

Fe + 2HCl = FeCl 2 + H 2

Fe + H 2 SO 4 = FeSO 4 + H 2

4. Interaction with “oxidizing” acids (HNO 3, H 2 SO 4 conc.)

Fe 0 - 3e - → Fe 3+

Concentrated HNO 3 and H 2 SO 4 “passivate” iron, so at ordinary temperatures the metal does not dissolve in them. With strong heating, slow dissolution occurs (without releasing H 2).

In the section HNO 3 iron dissolves, goes into solution in the form of Fe 3+ cations and the acid anion is reduced to NO*:

Fe + 4HNO 3 = Fe(NO 3) 3 + NO + 2H 2 O

Very soluble in a mixture of HCl and HNO 3

5. Relation to alkalis

Fe does not dissolve in aqueous solutions of alkalis. It reacts with molten alkalis only at very high temperatures.

6. Interaction with salts of less active metals

Fe + CuSO 4 = FeSO 4 + Cu

Fe 0 + Cu 2+ = Fe 2+ + Cu 0

7. Interaction with gaseous carbon monoxide (t = 200°C, P)

Fe (powder) + 5CO (g) = Fe 0 (CO) 5 iron pentacarbonyl

Fe(III) compounds

Fe 2 O 3 - iron (III) oxide.

Red-brown powder, n. R. in H 2 O. In nature - “red iron ore”.

Methods of obtaining:

1) decomposition of iron (III) hydroxide

2Fe(OH) 3 = Fe 2 O 3 + 3H 2 O

2) pyrite firing

4FeS 2 + 11O 2 = 8SO 2 + 2Fe 2 O 3

3) nitrate decomposition

Chemical properties

Fe 2 O 3 is a basic oxide with signs of amphotericity.

I. The main properties are manifested in the ability to react with acids:

Fe 2 O 3 + 6H + = 2Fe 3+ + ZH 2 O

Fe 2 O 3 + 6HCI = 2FeCI 3 + 3H 2 O

Fe 2 O 3 + 6HNO 3 = 2Fe(NO 3) 3 + 3H 2 O

II. Weak acid properties. Fe 2 O 3 does not dissolve in aqueous solutions of alkalis, but when fused with solid oxides, alkalis and carbonates, ferrites form:

Fe 2 O 3 + CaO = Ca(FeO 2) 2

Fe 2 O 3 + 2NaOH = 2NaFeO 2 + H 2 O

Fe 2 O 3 + MgCO 3 = Mg(FeO 2) 2 + CO 2

III. Fe 2 O 3 - feedstock for the production of iron in metallurgy:

Fe 2 O 3 + ZS = 2Fe + ZSO or Fe 2 O 3 + ZSO = 2Fe + ZSO 2

Fe(OH) 3 - iron (III) hydroxide

Methods of obtaining:

Obtained by the action of alkalis on soluble Fe 3+ salts:

FeCl 3 + 3NaOH = Fe(OH) 3 + 3NaCl

At the time of preparation, Fe(OH) 3 is a red-brown mucous-amorphous sediment.

Fe(III) hydroxide is also formed during the oxidation of Fe and Fe(OH) 2 in moist air:

4Fe + 6H 2 O + 3O 2 = 4Fe(OH) 3

4Fe(OH) 2 + 2H 2 O + O 2 = 4Fe(OH) 3

Fe(III) hydroxide is the end product of the hydrolysis of Fe 3+ salts.

Chemical properties

Fe(OH) 3 is a very weak base (much weaker than Fe(OH) 2). Shows noticeable acidic properties. Thus, Fe(OH) 3 has an amphoteric character:

1) reactions with acids occur easily:

2) fresh precipitate of Fe(OH) 3 dissolves in hot conc. solutions of KOH or NaOH with the formation of hydroxo complexes:

Fe(OH) 3 + 3KOH = K 3

In an alkaline solution, Fe(OH) 3 can be oxidized to ferrates (salts of iron acid H 2 FeO 4 not released in the free state):

2Fe(OH) 3 + 10KOH + 3Br 2 = 2K 2 FeO 4 + 6KBr + 8H 2 O

Fe 3+ salts

The most practically important are: Fe 2 (SO 4) 3, FeCl 3, Fe(NO 3) 3, Fe(SCN) 3, K 3 4 - yellow blood salt = Fe 4 3 Prussian blue (dark blue precipitate)

b) Fe 3+ + 3SCN - = Fe(SCN) 3 thiocyanate Fe(III) (blood red solution)

Definition. Story. Geochemistry. Properties of iron. Place of Birth. Physical and chemical properties. Connections. Use of iron.

Iron

Iron is an element of the eighth group (according to the old classification, a secondary subgroup of the eighth group) of the fourth period of the periodic table of chemical elements. I. Mendeleev with atomic number 26. Indicated by the symbol Fe(lat. Ferrum). One of the most common metals in the earth's crust (second place after aluminum).
The simple substance iron (CAS number: 7439-89-6) is a malleable silver-white metal with high chemical reactivity: iron quickly corrodes at high temperatures or high humidity in the air. Iron burns in pure oxygen, and in a finely dispersed state it spontaneously ignites in air.
Actually, iron is usually called its alloys with a low impurity content (up to 0.8%), which retain the softness and ductility of pure metal. But in practice, alloys of iron with carbon are more often used: steel (up to 2.14 wt.% carbon) and cast iron (more than 2.14 wt.% carbon), as well as stainless (alloy) steel with additions of alloying metals (chrome, manganese, nickel, etc.). The combination of specific properties of iron and its alloys make it “metal No. 1” in importance for humans.
In nature, iron is rarely found in its pure form; most often it is found in iron-nickel meteorites. The abundance of iron in the earth's crust is 4.65% (4th place after O, Si, Al). Iron is also believed to make up most of the earth's core.

Story. Iron, as a tool material, has been known since ancient times. The oldest iron objects 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 from 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 meteorite iron: “sider” (which means “stellar”).

Products made from iron obtained by smelting have been known since the settlement of the Aryan tribes from Europe to Asia, the islands of the Mediterranean Sea, and beyond (late 4th and 3rd millennium BC. The most ancient iron tools known are steel blades found in the stonework of the Cheops pyramid in Egypt (built around 2530 BC).As excavations in the Nubian Desert showed, already at that time the Egyptians, trying to separate the mined gold from heavy magnetite sand, calcined the ore with bran and similar substances containing carbon. As a result, a layer of doughy iron floated on the surface of the molten gold, which was processed separately. Tools were forged from this iron, including those found in the pyramid of Cheops. However, after Cheops' grandson Menkaure (2471-2465 BC) in Egypt, turmoil: 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 of 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 decline, and, just as the art of building pyramids degraded, the technology of iron production was lost, to the point that later, when exploring the Sinai Peninsula in search of copper ore, the Egyptians did not pay any attention to the deposits of iron ore that existed there, and received iron from the neighboring Hittites and Mitannians.
The first to master the Hatti method of smelting iron, 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 Hutts (modern Anatolia in Turkey). Thus, the text of the Hittite king Anitta (circa 1800 BC) says:
In ancient times, the Khalibs were known as masters of iron products. The legend of the Argonauts (their campaign in Colchis took place about 50 years before the Trojan War) tells that the king of Colchis, Eet, gave Jason an iron plow so that he could plow the field of Ares, and his subjects, the Calibers, are described:
They do not plow the land, do not plant fruit trees, do not graze flocks in rich meadows; they extract ore and iron from uncultivated land and exchange food for it. The day does not begin for them without hard work; they spend the whole day in the darkness of the night and thick smoke...
Aristotle described their method of producing steel: “the Khalibs washed the river sand of their country several times, thereby releasing black concentrate (a heavy fraction consisting mainly of magnetite and hematite), and smelted it in furnaces; The metal thus obtained had a silvery color and was stainless.”
As a raw material for steel smelting, magnetite sands were used, which are often found along the entire Black Sea coast: these magnetite sands consist of a mixture of small grains of magnetite, titanium-magnetite or ilmenite, and fragments of other rocks, so the steel smelted by the Khalibs was alloyed and had excellent properties. This unique method 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.
Clement of Alexandria in his encyclopedic work "Stromata" mentions that according to Greek legends, iron (apparently smelted from ore) was discovered on Mount Ida - that was the name of the mountain range near Troy (in the Iliad it is mentioned as Mount Ida, from which Zeus watched battle between the Greeks and the Trojans). This happened 73 years after the Deucalion flood, and this flood, according to the Parian Chronicle, took place in 1528 BC. e., that is, the method of smelting iron from ore was discovered around 1455 BC. e. However, from Clement’s description it is not clear whether he is talking about this particular mountain in Western Asia (Ida of Phrygia in Virgil), or about Mount Ida on the island of Crete, which the Roman poet Virgil writes in the Aeneid as the ancestral home of the Trojans:
“The island of Jupiter, Creta, lies in the middle of a wide sea,
Our tribe has its cradle there, where Ida rises..."
It is more likely that Clement of Alexandria is talking specifically about the Phrygian Ida near Troy, since ancient iron mines and centers of iron production were found there. The first written evidence of iron is found in clay tablets from the archives of the Egyptian pharaohs Amenhotep III and Akhenaten, and dates back to the same time (1450-1400 BC). It mentions the production of iron in the south of Transcaucasia, which the Greeks called Colchis (and it is possible that the word “kolhidos” may be a modification of the word “halibos”) - namely, what the king of the country of Mitanni and the ruler of Armenia and South Transcaucasia sent to the Egyptian pharaoh Amenhotep II " along with 318 concubines, daggers and rings made of good iron.” The Hittites also gave the same gifts to the pharaohs.
In very ancient times, iron was valued more than gold, and according to Strabo’s description, African tribes gave 10 pounds of gold for 1 pound of iron, and according to the research of 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, the biblical book of Deuteronomy 3.11 describes the “iron bed” of the Rephaim king Og.
In the tomb of Tutankhamun (circa 1350 BC) an iron dagger with a gold frame was found, possibly a gift from the Hittites for diplomatic purposes. But the Hittites did not strive for the widespread dissemination of iron and its technologies, as can be seen from the correspondence that has come down to us between the Egyptian pharaoh Tutankhamun and his father-in-law Hattusil, the king of the Hittites. The pharaoh asks to send more iron, and the king of the Hittites evasively replies that iron reserves have dried up, 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 made of “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, this is why iron products became widespread only after the Trojan War and the fall of the Hittite power, 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 mainly 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 a discus made of iron to the winner in a discus throwing competition. The Achaeans mined this iron from the Trojans and neighboring peoples (Iliad 7.473), including the Khalibs.
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 (biblical "PILISTIM", and these were proto-Greek tribes related to the later Hellenes, mainly Pelasgians) had many iron chariots, that is, in this At the time, iron had already become widely used in large quantities.
Homer calls iron difficult because in ancient times the main method of its production was the cheese-blowing process: alternating layers of iron ore and charcoal were calcined in special furnaces (furnaces - from the ancient “Horn” - horn, pipe, originally it was just a pipe dug in ground, usually horizontally in the slope of a ravine). In the forge, iron oxides are reduced to metal by hot coal, which takes up oxygen, oxidizing to carbon monoxide, and as a result of such calcination of ore with coal, dough-like krichine (sponge) iron was obtained. Kritsa was cleaned of slag by forging, squeezing out impurities with strong blows of a hammer. The first forges had a relatively low temperature - noticeably lower than the melting point of cast iron, so the iron turned out to be relatively low-carbon. To obtain strong steel, it was necessary to calcinate and forge the iron core with coal many times, while the surface layer of the metal was additionally saturated with carbon and strengthened. This is 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 to make more efficient furnaces (in Russian - blast furnace, domnitsa) for the production of steel, and used bellows to supply air to the furnace. Already the Romans knew how to bring the temperature in the furnace to melting steel (about 1400 degrees, and pure iron melts at 1535 degrees). This produces cast iron with a melting point of 1100-1200 degrees, which is very brittle in the solid state (not even forgeable) and does not have the elasticity of steel. Initially it was considered a harmful by-product, but then it was discovered that when re-melted in a furnace with increased air blowing through it, cast iron turns into good quality steel, as the excess carbon burns out. This two-stage process for producing steel from cast iron turned out to be simpler and more profitable than the critical one, and this principle has been used without much change for many centuries, remaining to this day the main method of producing iron materials.

Isotopes

Natural iron consists of four stable isotopes: 54Fe (isotopic abundance 5.845%), 56Fe (91.754%), 57Fe (2.119%) and 58Fe (0.282%). More than 20 unstable isotopes of iron are also known with mass numbers from 45 to 72, the most stable of which are 60Fe (half-life according to data updated in 2009 is 2.6 million years), 55Fe (2.737 years), 59Fe (44.495 days) and 52Fe (8.275 hours); other isotopes have half-lives of less than 10 minutes.
The iron isotope 56Fe is one of the most stable nuclei: all of the following elements can reduce the binding energy per nucleon through decay, and all previous elements, in principle, could reduce the binding energy per nucleon through fusion. It is believed that iron ends the series of synthesis of elements in the cores of normal stars, and all subsequent elements can only be formed as a result of supernova explosions.

Geochemistry of iron

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 iron content in the earth's crust is 5%, and in the mantle about 12%. Of the metals, iron is second only to aluminum in abundance in the bark. At the same time, about 86% of all iron is found in the core, and 14% in the mantle. The iron content increases significantly in mafic igneous rocks, where it is associated with pyroxene, amphibole, olivine and biotite. Iron accumulates in industrial concentrations during almost all exogenous and endogenous processes occurring in the earth's crust. Sea water contains iron in very small quantities, 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 - makes up the core of the earth, is possibly present in the mantle and is very rarely found in the earth's crust. Ferrous iron FeO is the main form of iron found in the mantle and crust. Iron oxide Fe2O3 is characteristic of the uppermost, most oxidized parts of the earth's crust, in particular sedimentary rocks.
In terms of crystal chemical properties, the Fe2+ ion is close to the Mg2+ and Ca2+ ions - other main elements that make up a significant part of all earthly rocks. Due to crystal chemical similarity, iron replaces magnesium and, partially, calcium in many silicates. In this case, the iron content in minerals of variable composition usually increases with decreasing temperature.
Iron minerals. Iron is quite widespread in the earth's crust - it accounts for about 4.1% of the mass of the earth's crust (4th place among all elements, 2nd among metals). In the mantle and earth's crust, iron is concentrated mainly in silicates, while its content is significant in basic and ultrabasic rocks, and low in acidic and intermediate rocks.
A large number of ores and minerals containing iron are known. Of greatest practical importance are red iron ore (hematite, Fe2O3; contains up to 70% Fe), magnetic iron ore (magnetite, FeFe2O4, Fe3O4; contains 72.4% Fe), brown iron ore or limonite (goethite and hydrogoethite, respectively FeOOH and FeOOH nH2O ). Goethite and hydrogoethite are most often found in weathering crusts, forming 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 Fe3(PO4)2·8H2O is often found in them, forming black elongated crystals and radial aggregates.
Iron sulfides are also widespread in nature - pyrite FeS2 (sulfur or iron pyrite) and pyrrhotite. They are not iron ore - pyrite is used to make sulfuric acid, and pyrrhotite often contains nickel and cobalt.
Russia ranks first in the world in terms of iron ore reserves.
The iron content in sea water is 1·10−5—1·10−8%.
Other commonly found iron minerals:

• Siderite - FeCO3 - contains approximately 35% iron. It has a yellowish-white (with a gray or brown tint if dirty) color. The density is 3 g/cm³ and the hardness is 3.5-4.5 on the Mohs scale.
• Marcasite - FeS2 - contains 46.6% iron. It occurs in the form of yellow, brass-like, bipyramidal rhombic crystals with a density of 4.6-4.9 g/cm³ and a hardness of 5-6 on the Mohs scale.
• Löllingite - FeAs2 - contains 27.2% iron and occurs in the form of silvery-white bipyramidal rhombic crystals. Density is 7-7.4 g/cm³, hardness 5-5.5 on the Mohs scale.
• Mispickel - 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.
• Melantherite - FeSO4 7H2O - is less common in nature and is green (or gray due to impurities) monoclinic crystals with a glassy luster and fragile. The density is 1.8-1.9 g/cm³.
• Vivianite - Fe3(PO4)2 8H2O - 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.

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 located in Brazil (1st place), Australia, USA, Canada, Sweden, Venezuela, Liberia, Ukraine, France, India. In Russia, iron is mined in the Kursk Magnetic Anomaly (KMA), the Kola Peninsula, Karelia and Siberia, in Ukraine - Krivbass, Poltava region, Kerch Peninsula. Bottom ocean deposits, in which iron, together with manganese and other valuable metals, are found in nodules, have recently acquired a significant role.

Receipt. Industrially, iron is obtained from iron ore, mainly hematite (Fe2O3) and magnetite (FeO Fe2O3).

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 agglomerate or pellets, and flux (such as limestone) are fed from above, and are met by a stream of forced hot air from below.
In the furnace, carbon in the form of coke is oxidized to carbon monoxide. This oxide is formed during combustion in a lack of oxygen:

In turn, carbon monoxide reduces iron from the ore. To make this reaction go faster, heated carbon monoxide is passed through iron(III) oxide:

Flux is added to get rid of unwanted impurities (primarily silicates; for example, quartz) in the mined ore. A typical flux contains limestone (calcium carbonate) and dolomite (magnesium carbonate). To remove other impurities, other fluxes are used.
The effect of flux (in this case calcium carbonate) is that when it is heated, it decomposes to its oxide:

Calcium oxide combines with silicon dioxide, forming slag - calcium metasilicate:

Slag, unlike silicon dioxide, is melted in a furnace. Slag, lighter than iron, floats on the surface - this property allows you to separate the slag from the metal. The slag can then be used in construction and agriculture. The molten iron produced in a blast furnace contains quite a lot of carbon (cast iron). Except in cases where cast iron is used directly, it requires further processing.
Excess carbon and other impurities (sulfur, phosphorus) are removed from cast iron by oxidation in open-hearth furnaces or converters. Electric furnaces are also used for smelting alloy steels.
In addition to the blast furnace process, the process of direct iron production is common. In this case, pre-crushed ore is mixed with special clay, forming pellets. The pellets are fired and treated in a shaft furnace with hot methane conversion products, which contain hydrogen. Hydrogen easily reduces iron:
,
in this case, the iron does not become contaminated with such impurities as sulfur and phosphorus, which are common impurities in coal. Iron is obtained in solid form and is subsequently melted in electric furnaces.
Chemically pure iron is obtained by electrolysis of solutions of its salts.

Physical properties

Iron is a typical metal; in its free state it is silvery-white in color with a grayish tint. Pure metal is ductile; various impurities (in particular carbon) increase its hardness and brittleness. It has pronounced magnetic properties. The so-called “iron triad” is often distinguished - a group of three metals (iron Fe, cobalt Co, nickel Ni) with similar physical properties, atomic radii and electronegativity values.
Iron is characterized by polymorphism; it has four crystalline modifications:

• up to 769 °C there is α-Fe (ferrite) with a body-centered cubic lattice and ferromagnetic properties (769 °C ≈ 1043 K - the Curie point for iron);
• in the temperature range 769–917 °C there is β-Fe, which differs from α-Fe only in the parameters of the body-centered cubic lattice and the magnetic properties of the paramagnet;
• in the temperature range 917–1394 °C there is γ-Fe (austenite) with a face-centered cubic lattice;
• above 1394 °C δ-Fe with a body-centered cubic lattice is stable.

Metallurgy does not distinguish β-Fe as a separate phase, and considers it as a variety of α-Fe. When iron or steel is heated above the Curie point (769 °C ≈ 1043 K), the thermal movement of ions upsets the orientation of the spin magnetic moments of the electrons, the ferromagnet becomes paramagnetic - a second-order phase transition occurs, but a first-order phase transition with a change in the basic physical parameters of the crystals does not occur.
For pure iron at normal pressure, from the point of view of metallurgy, there are the following stable modifications:

• from absolute zero to 910 °C, the α-modification with a body-centered cubic (bcc) crystal lattice is stable;
• from 910 to 1400 °C the γ-modification with a face-centered cubic (fcc) crystal lattice is stable;
• from 1400 to 1539 °C the δ modification with a body-centered cubic (bcc) crystal lattice is stable.

The presence of carbon and alloying elements in steel significantly changes the temperatures of phase transitions (see iron-carbon phase diagram). A solid solution of carbon in α- and δ-iron is called ferrite. A distinction is sometimes made between high-temperature δ-ferrite and low-temperature α-ferrite (or simply ferrite), although their atomic structures are the same. A solid solution of carbon in γ-iron is called austenite.

• In the region of high pressures (over 13 GPa, 128.3 thousand atm.), a modification of ε-iron with a hexagonal close-packed (hcp) lattice appears.

The phenomenon of polymorphism is extremely important for steel metallurgy. It is thanks to α-γ transitions in the crystal lattice that 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 the series of standard electrode potentials, iron is ranked before hydrogen and easily reacts with dilute acids. Thus, iron belongs to the metals of intermediate activity.
The melting point of iron is 1539 °C, the boiling point is 2862 °C.

Chemical properties

Characteristic oxidation states

Iron is characterized by iron oxidation states - +2 and +3.
The oxidation state +2 corresponds to black oxide FeO and green hydroxide Fe(OH)2. They are basic in nature. In salts, Fe(+2) is present as a cation. Fe(+2) is a weak reducing agent.
The oxidation state +3 corresponds to the red-brown oxide Fe2O3 and the brown hydroxide Fe(OH)3. They are amphoteric in nature, although acidic, and their basic properties are weakly expressed. Thus, Fe3+ ions are completely hydrolyzed even in an acidic environment. Fe(OH)3 dissolves (and even then not completely) only in concentrated alkalis. Fe2O3 reacts with alkalis only upon fusion, giving ferrites (formal salts of the acid HFeO2, which does not exist in free form):

Iron (+3) most often exhibits weak oxidizing properties.
Oxidation states +2 and +3 easily change between each other when redox conditions change.
In addition, there is the oxide Fe3O4, 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+3O2)2.
There is also an oxidation state of +6. The corresponding oxide and hydroxide do not exist in free form, but salts are obtained - ferrates (for example, K2FeO4). Iron (+6) is present in them in the form of an anion. Ferrates are strong oxidizing agents.

Iron(II) compounds

Iron(II) oxide FeO has basic properties; the base Fe(OH)2 corresponds to it. Iron (II) salts have a light green color. When stored, especially in humid air, they turn brown due to oxidation to iron (III). The same process occurs when storing aqueous solutions of iron(II) salts:

Of the iron(II) salts, the most stable in aqueous solutions is Mohr's salt—double ammonium and iron(II) sulfate (NH4)2Fe(SO4)2 6H2O.
Potassium hexacyanoferrate(III) K3 (red blood salt) can serve as a reagent for Fe2+ ions in solution. When Fe2+ and 3− ions interact, a precipitate of potassium iron (II) hexacyanoferrate (III) (Prussian blue) precipitates:

which rearranges intramolecularly into potassium iron(III) hexacyanoferrate(II):

For the quantitative determination of iron (II) in solution, phenanthroline Phen is used, which forms a red complex FePhen3 with iron (II) (maximum light absorption - 520 nm) in a wide pH range (4-9).

Iron(III) compounds

Iron(III) oxide Fe2O3 is weakly amphoteric; it is matched by an even weaker base than Fe(OH)2, Fe(OH)3, which reacts with acids:

Fe3+ salts are prone to the formation of crystalline hydrates. In them, the Fe3+ ion is usually surrounded by six water molecules. These salts are pink or purple in color.
The Fe3+ ion is completely hydrolyzed even in an acidic environment. At pH>4, this ion is almost completely precipitated in the form of Fe(OH)3:

With partial hydrolysis of the Fe3+ ion, polynuclear oxo- and hydroxocations are formed, which is why the solutions turn brown.
The basic properties of iron(III) hydroxide Fe(OH)3 are very weakly expressed. It is capable of reacting only with concentrated solutions of alkalis:

The resulting hydroxo complexes of iron(III) are stable only in strongly alkaline solutions. When solutions are diluted with water, they are destroyed, and Fe(OH)3 precipitates.
When alloyed with alkalis and oxides of other metals, Fe2O3 forms a variety of ferrites:

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

Iron(III) is capable of forming double sulfates with singly charged cations such as alum, for example, KFe(SO4)2 - iron-potassium alum, (NH4)Fe(SO4)2 - iron-ammonium alum, etc.
For qualitative detection of iron(III) compounds in solution, a qualitative reaction of Fe3+ ions with inorganic thiocyanates SCN− is used. In this case, a mixture of bright red thiocyanate iron complexes 2+, +, Fe(SCN)3, - is formed. The composition of the mixture (and therefore the intensity of its color) depends on various factors, therefore this method is not applicable for accurate qualitative determination of iron.
Another high-quality reagent for Fe3+ ions is potassium hexacyanoferrate(II) K4 (yellow blood salt). When Fe3+ and 4− ions interact, a bright blue precipitate of potassium iron (III) hexacyanoferrate (II) is formed:

Fe3+ ions are quantitatively determined by the formation of red (in a slightly acidic environment) or yellow (in a slightly alkaline environment) complexes with sulfosalicylic acid. This reaction requires proper selection of buffers, since some anions (in particular, acetate) form mixed complexes with iron and sulfosalicylic acid with their own optical characteristics.

Iron(VI) compounds

Ferrates are salts of iron acid H2FeO4, which does not exist in free form. These are violet-colored compounds, reminiscent of permanganates in oxidative properties, and sulfates in solubility. Ferrates are obtained by the action of gaseous chlorine or ozone on a suspension of Fe(OH)3 in alkali:

Ferrates can also be obtained by electrolysis of a 30% alkali solution on an iron anode:

Ferrates are strong oxidizing agents. In an acidic environment they decompose with the release of oxygen:

The oxidizing properties of ferrates are used to disinfect water.

Application

Iron is one of the most used metals, accounting for up to 95% of global 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 production 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. This uses both the black color of the magnetite and its ability to stick to the magnetized transfer roller.
• The unique ferromagnetic properties of a number of iron-based alloys contribute to their widespread use in electrical engineering for 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 heptate (ferrous sulfate) mixed with copper sulfate is used to combat harmful fungi in gardening and construction.
• Iron is used as an anode in iron-nickel batteries and iron-air batteries.
• Aqueous solutions of ferrous and ferric chlorides, as well as its sulfates, are used as coagulants in the purification processes of natural and waste water in the water treatment of industrial enterprises.