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Iron(III) oxide or ferric oxide is the
inorganic compound In chemistry Chemistry is the study of the properties and behavior of . It is a that covers the that make up matter to the composed of s, s and s: their composition, structure, properties, behavior and the changes they undergo during a ...
with the formula Fe2O3. It is one of the three main
oxide An oxide () is a chemical compound A chemical compound is a chemical substance composed of many identical molecules (or molecular entity, molecular entities) composed of atoms from more than one chemical element, element held together by che ...
s of
iron Iron () is a with Fe (from la, ) and 26. It is a that belongs to the and of the . It is, on , right in front of (32.1% and 30.1%, respectively), forming much of Earth's and . It is the fourth most common . In its metallic state, iron ...

iron
, the other two being
iron(II) oxide Iron(II) oxide or ferrous oxide is the inorganic compound with the formula FeO. Its mineral form is known as wüstite.https://www.mindat.org/min-4316.htmlhttps://www.ima-mineralogy.org/Minlist.htm One of several iron oxides, it is a black-colored ...

iron(II) oxide
(FeO), which is rare; and
iron(II,III) oxide Iron(II,III) oxide is the chemical compound with formula Fe3O4. It occurs in nature as the mineral magnetite Magnetite is a mineral and one of the main iron ore Iron ores are rocks and minerals from which metal A metal (from Ancient Gr ...
(Fe3O4), which also occurs naturally as the mineral
magnetite Magnetite is a mineral In geology Geology (from the Ancient Greek γῆ, ''gē'' ("earth") and -λoγία, ''-logia'', ("study of", "discourse")) is an Earth science concerned with the solid Earth, the rock (geology), rocks of which it i ...

magnetite
. As the mineral known as
hematite Hematite (), also spelled as haematite, is a common iron oxide Iron oxides are chemical compounds composed of iron and oxygen Oxygen is the chemical element with the chemical symbol, symbol O and atomic number 8. It is a member o ...

hematite
, Fe2O3 is the main source of iron for the steel industry. Fe2O3 is readily attacked by acids. Iron(III) oxide is often called
rust Rust is an iron oxide, a usually reddish-brown oxide formed by the reaction of iron and oxygen in the catalytic presence of water or air moisture. Rust consists of hydrous ferric oxides, hydrous iron(III) oxides (Fe2O3·nH2O) and iron(III) oxi ...

rust
, and to some extent this label is useful, because rust shares several properties and has a similar composition; however, in chemistry, rust is considered an ill-defined material, described as Hydrous ferric oxide.


Structure

Fe2O3 can be obtained in various polymorphs. In the main one, α, iron adopts octahedral coordination geometry. That is, each Fe center is bound to six oxygen
ligand In coordination chemistry A coordination complex consists of a central atom An atom is the smallest unit of ordinary matter In classical physics and general chemistry, matter is any substance that has mass and takes up space by havi ...
s. In the γ polymorph, some of the Fe sit on tetrahedral sites, with four oxygen ligands.


Alpha phase

α-Fe2O3 has the
rhombohedral In geometry, a rhombohedron (also called a rhombic hexahedron) is a three-dimensional figure with six faces which are rhombus, rhombi. It is a special case of a parallelepiped where all edges are the same length. It can be used to define the rhom ...
,
corundum Corundum is a crystal A crystal or crystalline solid is a solid Solid is one of the four fundamental states of matter (the others being liquid A liquid is a nearly incompressible fluid In physics, a fluid is a substance th ...

corundum
(α-Al2O3) structure and is the most common form. It occurs naturally as the mineral
hematite Hematite (), also spelled as haematite, is a common iron oxide Iron oxides are chemical compounds composed of iron and oxygen Oxygen is the chemical element with the chemical symbol, symbol O and atomic number 8. It is a member o ...

hematite
which is mined as the main
ore ore – psilomelane Psilomelane is a group name for hard black manganese oxides including hollandite and romanechite. Psilomelane consists of hydrous manganese Manganese is a chemical element Image:Simple Periodic Table Chart- ...

ore
of iron. It is
antiferromagnetic Antiferromagnetic ordering In materials that exhibit antiferromagnetism, the magnetic moment The magnetic moment is the magnetic strength and orientation of a magnet or other object that produces a magnetic field A magnetic field is a vec ...
below ~260 K (
Morin transitionThe Morin transition (also known as a spin-flop transition) is a magnetic phase transition In chemistry, thermodynamics, and many other related fields, phase transitions (or phase changes) are the Physical process, physical processes of transition ...
temperature), and exhibits weak
ferromagnetism Ferromagnetism is the basic mechanism by which certain materials (such as iron Iron () is a chemical element with Symbol (chemistry), symbol Fe (from la, Wikt:ferrum, ferrum) and atomic number 26. It is a metal that belongs to the first tr ...
between 260 K and the
Néel temperature In physics and materials science, the Curie temperature (''T''C), or Curie point, is the temperature above which certain materials lose their magnet, permanent magnetic properties, which can (in most cases) be replaced by magnetization, induced ...
, 950 K. It is easy to prepare using both
thermal decomposition Thermal decomposition, or thermolysis, is a chemical decompositionChemical decomposition, or chemical breakdown, is the process or effect of simplifying a single chemical entity (normal molecule, reaction intermediate, etc.) into two or more fra ...
and precipitation in the liquid phase. Its magnetic properties are dependent on many factors, e.g. pressure, particle size, and magnetic field intensity.


Gamma phase

γ-Fe2O3 has a
cubic Cubic may refer to: Science and mathematics * Cube (algebra) In arithmetic and algebra Algebra (from ar, الجبر, lit=reunion of broken parts, bonesetting, translit=al-jabr) is one of the areas of mathematics, broad areas of mathema ...
structure. It is metastable and converted from the alpha phase at high temperatures. It occurs naturally as the mineral
maghemite Maghemite (Fe2O3, γ-Fe2O3) is a member of the family of iron oxide Iron oxides are chemical compounds composed of iron and oxygen Oxygen is the chemical element with the chemical symbol, symbol O and atomic number 8. It is a membe ...
. It is
ferromagnetic Ferromagnetism is the basic mechanism by which certain materials (such as iron Iron () is a with Fe (from la, ) and 26. It is a that belongs to the and of the . It is, on , right in front of (32.1% and 30.1%, respectively), formi ...
and finds application in recording tapes, although
ultrafine particlesUltrafine particles (UFPs) are particulate matter of nanoscale size (less than 0.1 μm or 100 nm in diameter). Regulations do not exist for this size class of ambient air pollution particles, which are far smaller than the regulated PM10 and ...
smaller than 10 nanometers are
superparamagnetic Superparamagnetism is a form of magnetism Magnetism is a class of physical phenomena that are mediated by magnetic field A magnetic field is a vector field that describes the magnetic influence on moving electric charges, electric currents, ...
. It can be prepared by thermal dehydratation of gamma
iron(III) oxide-hydroxide Iron(III) oxide-hydroxide or ferric oxyhydroxideA. L. Mackay (1960): "β-Ferric Oxyhydroxide". ''Mineralogical Magazine'' (''Journal of the Mineralogical Society''), volume 32, issue 250, pages 545-557. is the chemical compound of iron Iron ...
. Another method involves the careful oxidation of
iron(II,III) oxide Iron(II,III) oxide is the chemical compound with formula Fe3O4. It occurs in nature as the mineral magnetite Magnetite is a mineral and one of the main iron ore Iron ores are rocks and minerals from which metal A metal (from Ancient Gr ...
(Fe3O4). The ultrafine particles can be prepared by thermal decomposition of
iron(III) oxalate Ferric oxalate, also known as iron(III) oxalate, is a chemical compound composed of ferric ions and oxalate ligands; it may also be regarded as the ferric salt of oxalic acid. The anhydrous material is pale yellow; however, it may be hydrated to fo ...
.


Other solid phases

Several other phases have been identified or claimed. The β-phase is cubic body-centered (space group Ia3),
metastable In chemistry and physics, metastability denotes an intermediate energetic state within a dynamical system other than the system's ground state, state of least energy. A ball resting in a hollow on a slope is a simple example of metastability. I ...

metastable
, and at temperatures above converts to alpha phase. It can be prepared by reduction of hematite by carbon,
pyrolysis The pyrolysis (or devolatilization) process is the thermal decomposition Thermal decomposition, or thermolysis, is a chemical decompositionChemical decomposition, or chemical breakdown, is the process or effect of simplifying a single chemica ...

pyrolysis
of
iron(III) chloride Iron(III) chloride is the inorganic compound with the formula (). Also called ferric chloride, it is a common compound of iron in the +3 oxidation state The oxidation state, or oxidation number, is the hypothetical charge Charge or charged may re ...
solution, or thermal decomposition of
iron(III) sulfate Iron(III) sulfate (or ferric sulfate), is a family of inorganic compound In chemistry Chemistry is the scientific discipline involved with Chemical element, elements and chemical compound, compounds composed of atoms, molecules and ions: the ...
. The epsilon (ε) phase is rhombic, and shows properties intermediate between alpha and gamma, and may have useful magnetic properties applicable for purposes such as high density
recording media On a reel-to-reel tape recorder (Sony TC-630), the recorder is data storage equipment and the magnetic tape is a data storage medium. Data Data are units of information Information can be thought of as the resolution of uncertaint ...
for
big data Big data is a field that treats ways to analyze, systematically extract information from, or otherwise deal with data set A data set (or dataset) is a collection of data Data (; ) are individual facts, statistics, or items of informati ...

big data
storage. Preparation of the pure epsilon phase has proven very challenging. Material with a high proportion of epsilon phase can be prepared by thermal transformation of the gamma phase. The epsilon phase is also metastable, transforming to the alpha phase at between . It can also be prepared by oxidation of iron in an
electric arc An electric arc, or arc discharge, is an electrical breakdown of a gas that produces a prolonged electrical discharge. The electric current, current through a normally Electrical conductance, nonconductive medium such as air produces a plasma (ph ...

electric arc
or by sol-gel precipitation from
iron(III) nitrate Iron(III) nitrate, or ferric nitrate, is the chemical compound with the formula Fe(NO3)3. Hydrates Iron(III) nitrate is deliquescence, deliquescent, and it is commonly found as the nonahydrate Fe(NO3)3·water of crystallization, 9H2O, which forms ...
. Research has revealed epsilon iron(III) oxide in ancient Chinese Jian ceramic glazes, which may provide insight into ways to produce that form in the lab. Additionally, at high pressure an
amorphous In condensed matter physics Condensed matter physics is the field of that deals with the macroscopic and microscopic physical properties of , especially the and which arise from forces between s. More generally, the subject deals with " ...

amorphous
form is claimed.


Liquid phase

Molten Fe2O3 is expected to have a coordination number of close to 5 oxygen atoms about each iron atom, based on measurements of slightly oxygen deficient supercooled liquid iron oxide droplets, where supercooling circumvents the need for the high oxygen pressures required above the melting point to maintain stoichiometry.


Hydrated iron(III) oxides

Several hydrates of Iron(III) oxide exists. When alkali is added to solutions of soluble Fe(III) salts, a red-brown gelatinous precipitate forms. This is ''not'' Fe(OH)3, but Fe2O3·H2O (also written as Fe(O)OH). Several forms of the hydrated oxide of Fe(III) exist as well. The red ''lepidocrocite'' γ-Fe(O)OH, occurs on the outside of
rusticle A rusticle is a formation of rust Rust is an iron oxide Iron oxides are chemical compounds composed of iron and oxygen Oxygen is the chemical element with the chemical symbol, symbol O and atomic number 8. It is a member of th ...
s, and the orange ''goethite'', which occurs internally in rusticles. When Fe2O3·H2O is heated, it loses its water of hydration. Further heating at 1670 K converts Fe2O3 to black Fe3O4 (FeIIFeIII2O4), which is known as the mineral ''magnetite''. Fe(O)OH is soluble in acids, giving . In concentrated aqueous alkali, Fe2O3 gives e(OH)6sup>3−.


Reactions

The most important reaction is its
carbothermal reduction Carbothermic reactions involve the reduction of substances, often metal oxides (O^2-), using carbon Carbon (from la, carbo "coal") is a with the C and 6. It is lic and —making four s available to form s. It belongs to group 14 of the ...
, which gives iron used in steel-making: : Fe2O3 + 3 CO → 2 Fe + 3 CO2 Another redox reaction is the extremely
exothermic In thermodynamics Thermodynamics is a branch of physics that deals with heat, Work (thermodynamics), work, and temperature, and their relation to energy, entropy, and the physical properties of matter and radiation. The behavior of these qu ...

exothermic
thermite Thermite () is a pyrotechnic composition A pyrotechnic composition is a substance or mixture of substances designed to produce an effect by heat, light, sound, gas/smoke or a combination of these, as a result of non-detonative self-sustaining ...

thermite
reaction with
aluminium Aluminium (aluminum in and ) is a with the  Al and  13. Aluminium has a density lower than those of other common , at approximately one third that of . It has a great affinity towards , and of on the surface when exposed to air ...

aluminium
. : 2 Al + Fe2O3 → 2 Fe + Al2O3 This process is used to weld thick metals such as rails of train tracks by using a ceramic container to funnel the molten iron in between two sections of rail. Thermite is also used in weapons and making small-scale cast-iron sculptures and tools. Partial reduction with hydrogen at about 400 °C produces magnetite, a black magnetic material that contains both Fe(III) and Fe(II): :3 Fe2O3 + H2 → 2 Fe3O4 + H2O Iron(III) oxide is insoluble in water but dissolves readily in strong acid, e.g. hydrochloric and
sulfuric acid Sulfuric acid (American spelling Despite the various English dialects spoken from country to country and within different regions of the same country, there are only slight regional variations in English orthography English orthogra ...

sulfuric acid
s. It also dissolves well in solutions of chelating agents such as
EDTA Ethylenediaminetetraacetic acid (EDTA) is an aminopolycarboxylic acid left, 120px, a metal complex with the EDTA anion file:Asparaginsäure - Aspartic acid.svg, 120px, Aspartic acid is an aminodicarboxylic acid and precursor to other ligands. An ...

EDTA
and
oxalic acid Oxalic acid is an organic acid An organic acid is an with ic properties. The most common organic acids are the s, whose acidity is associated with their  –COOH. s, containing the group –SO2OH, are relatively stronger acids. Alcoh ...

oxalic acid
. Heating iron(III) oxides with other metal oxides or carbonates yields materials known as
ferrateFerrate loosely refers to a material that can be viewed as containing anionic iron Iron () is a chemical element with Symbol (chemistry), symbol Fe (from la, Wikt:ferrum, ferrum) and atomic number 26. It is a metal that belongs to the first tran ...
s (ferrate (III)): : ZnO + Fe2O3 → Zn(FeO2)2


Preparation

Iron(III) oxide is a product of the oxidation of iron. It can be prepared in the laboratory by electrolyzing a solution of
sodium bicarbonate Sodium bicarbonate ( IUPAC name: sodium hydrogen carbonate), commonly known as baking soda or bicarbonate of soda, is a chemical compound with the formula NaHCO3. It is a salt composed of a sodium cation (Na+) and a bicarbonate anion ( HCO3 ...

sodium bicarbonate
, an inert electrolyte, with an iron anode: :4 Fe + 3 O2 + 2 H2O → 4 FeO(OH) The resulting hydrated iron(III) oxide, written here as FeO(OH), dehydrates around 200 °C.Handbook of Preparative Inorganic Chemistry, 2nd Ed. Edited by G. Brauer, Academic Press, 1963, NY. Vol. 1. p. 1661. :2 FeO(OH) → Fe2O3 + H2O


Uses


Iron industry

The overwhelming application of iron(III) oxide is as the feedstock of the steel and iron industries, e.g. the production of iron, steel, and many alloys.


Polishing

A very fine powder of ferric oxide is known as "jeweler's rouge", "red rouge", or simply rouge. It is used to put the final polish on metallic
jewelry Jewellery or jewelry consists of decorative items worn for personal adornment 150px, The principal adornment of these girls from the Bundu tribe in Sierra Leone is the adornment of bodies and faces with markings produced by the smearing on by ...

jewelry
and
lenses A lens is a transmissive optics, optical device that focuses or disperses a light beam by means of refraction. A simple lens consists of a single piece of transparent material, while a #Compound lenses, compound lens consists of several simple ...

lenses
, and historically as a
cosmetic Cosmetic may refer to: *Cosmetics, or make-up, substances to enhance the beauty of the human body, apart from simple cleaning *Cosmetic, an adjective describing beauty, aesthetics, or appearance, especially concerning the human body *Cosmetic, a top ...
. Rouge cuts more slowly than some modern polishes, such as
cerium(IV) oxide Cerium(IV) oxide, also known as ceric oxide, ceric dioxide, ceria, cerium oxide or cerium dioxide, is an oxide An oxide () is a chemical compound A chemical compound is a chemical substance A chemical substance is a form of matter ...

cerium(IV) oxide
, but is still used in optics fabrication and by jewelers for the superior finish it can produce. When polishing gold, the rouge slightly stains the gold, which contributes to the appearance of the finished piece. Rouge is sold as a powder, paste, laced on polishing cloths, or solid bar (with a
wax Waxes are a diverse class of organic compound In chemistry Chemistry is the study of the properties and behavior of . It is a that covers the that make up matter to the composed of s, s and s: their composition, structure, prope ...
or binder). Other polishing compounds are also often called "rouge", even when they do not contain iron oxide. Jewelers remove the residual rouge on jewelry by use of
ultrasonic cleaning Ultrasonic cleaning is a process that uses ultrasound Ultrasound is sound waves with frequency, frequencies higher than the upper audible limit of human hearing range, hearing. Ultrasound is not different from "normal" (audible) sound in its ...
. Products sold as " stropping compound" are often applied to a leather strop to assist in getting a razor edge on knives, straight razors, or any other edged tool.


Pigment

Iron(III) oxide is also used as a
pigment A pigment is a colored material that is completely or nearly insoluble in water. In contrast, dyes are typically soluble, at least at some stage in their use. Generally dyes are often organic compound , CH4; is among the simplest organic compou ...
, under names "Pigment Brown 6", "Pigment Brown 7", and "Pigment Red 101". Some of them, e.g. Pigment Red 101 and Pigment Brown 6, are approved by the US
Food and Drug Administration The United States The United States of America (U.S.A. or USA), commonly known as the United States (U.S. or US) or America, is a country Continental United States, primarily located in North America. It consists of 50 U.S. state, st ...
(FDA) for use in cosmetics.
Iron oxides Iron oxides are chemical compound A chemical compound is a chemical substance composed of many identical molecules (or molecular entity, molecular entities) composed of atoms from more than one chemical element, element held together by chemi ...

Iron oxides
are used as pigments in dental composites alongside titanium oxides. Hematite is the characteristic component of the Swedish paint color
Falu red Image:Keittomaalilla maalattu hirsitalo Äänekoskella.jpg, A traditional Finnish falu red log house in Äänekoski, Central Finland Falu red or falun red ( ; sv, falu rödfärg, ) is a dye that is used in a deep red paint, well known for its use o ...
.


Magnetic recording

Iron(III) oxide was the most common
magnet A magnet is a material or object that produces a magnetic field A magnetic field is a vector field In vector calculus and physics, a vector field is an assignment of a vector to each point in a subset of space. For instance, a ve ...

magnet
ic particle used in all types of magnetic storage and recording media, including magnetic disks (for data storage) and
magnetic tape Magnetic tape is a medium for , made of a thin, magnetizable coating on a long, narrow strip of . It was developed in Germany in 1928, based on . Devices that record and playback audio and video using magnetic tape are s and s respectively. A ...

magnetic tape
(used in audio and video recording as well as data storage). Its use in computer disks was superseded by cobalt alloy, enabling thinner magnetic films with higher storage density.


Photocatalysis

α-Fe2O3 has been studied as a
photoanode A "photoelectrochemical cell" is one of two distinct classes of device. The first electricity generation, produces electrical energy similarly to a dye-sensitized solar cell, dye-sensitized photovoltaic cell, which meets the standard definition of ...
for solar water oxidation. However, its efficacy is limited by a short diffusion length (2-4 nm) of photo-excited charge carriers and subsequent fast recombination, requiring a large
overpotential In electrochemistry Electrochemistry is the branch of physical chemistry Physical chemistry is the study of macroscopic The macroscopic scale is the length scale on which objects or phenomena are large enough to be visible with the naked ...
to drive the reaction. Research has been focused on improving the water oxidation performance of Fe2O3 using nanostructuring, surface functionalization, or by employing alternate crystal phases such as β-Fe2O3.


Medicine

Calamine Calamine, also known as calamine lotion, is a medication used to treat mild itchiness Itch (also known as pruritus or automatic tickle) is a sensation that causes the desire or reflex In biology Biology is the natural science that stu ...
lotion, used to treat mild
itch ITCH is a HECT domain In molecular biology, the HECT domain is a protein domain A protein domain is a region of the protein's Peptide, polypeptide chain that is self-stabilizing and that folds independently from the rest. Each domain forms a c ...

itch
iness, is chiefly composed of a combination of
zinc oxide Zinc oxide is an inorganic compound In chemistry Chemistry is the study of the properties and behavior of . It is a that covers the that make up matter to the composed of s, s and s: their composition, structure, properties, behavior ...

zinc oxide
, acting as
astringent An astringent (sometimes called adstringent) is a chemical that shrinks or constricts body tissue In biology Biology is the natural science that studies life and living organisms, including their anatomy, physical structure, Biochemi ...
, and about 0.5% iron(III) oxide, the product's active ingredient, acting as
antipruriticAntipruritics, also known as anti-itch drugs, are medication A medication (also referred to as medicine, pharmaceutical drug, medicinal drug or simply drug) is a drug used to medical diagnosis, diagnose, cure, therapy, treat, or preventive medi ...
. The red color of iron(III) oxide is also mainly responsible for the lotion's pink color.


See also

* Chalcanthum


References

https://external-content.duckduckgo.com/iu/?u=https%3A%2F%2Ftse3.explicit.bing.net%2Fth%3Fid%3DOIP.KeDnbqhqCtAAs5GZo5qNzQAAAA%26pid%3DApi&f=1


External links


NIOSH Pocket Guide to Chemical Hazards
{{DEFAULTSORT:Iron(Iii) Oxide E-number additives Iron oxide pigments Iron(III) compounds Transition metal oxides Sesquioxides