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=                              Aluminum                              =
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                            Introduction
======================================================================
Aluminium (or aluminum in North American English) is a chemical
element; it has symbol Al and atomic number 13. It has a density lower
than that of other common metals, about one-third that of steel.
Aluminium has a great affinity towards oxygen, forming a protective
layer of oxide on the surface when exposed to air. It visually
resembles silver, both in its color and in its great ability to
reflect light. It is soft, nonmagnetic, and ductile. It has one stable
isotope, 27Al, which is highly abundant, making aluminium the
12th-most abundant element in the universe. The radioactivity of 26Al
leads to it being used in radiometric dating.

Chemically, aluminium is a post-transition metal in the boron group;
as is common for the group, aluminium forms compounds primarily in the
+3 oxidation state. The aluminium cation Al3+ is small and highly
charged; as such, it has more polarizing power, and bonds formed by
aluminium have a more covalent character. The strong affinity of
aluminium for oxygen leads to the common occurrence of its oxides in
nature. Aluminium is found on Earth primarily in rocks in the crust,
where it is the third-most abundant element, after oxygen and silicon,
rather than in the mantle, and virtually never as the free metal. It
is obtained industrially by mining bauxite, a sedimentary rock rich in
aluminium minerals.

The discovery of aluminium was announced in 1825 by Danish physicist
Hans Christian Ørsted. The first industrial production of aluminium
was initiated by French chemist Henri Étienne Sainte-Claire Deville in
1856. Aluminium became much more available to the public with the
Hall-Héroult process developed independently by French engineer Paul
Héroult and American engineer Charles Martin Hall in 1886, and the
mass production of aluminium led to its extensive use in industry and
everyday life. In the First and Second World Wars, aluminium was a
crucial strategic resource for aviation. In 1954, aluminium became the
most produced non-ferrous metal, surpassing copper. In the 21st
century, most aluminium was consumed in transportation, engineering,
construction, and packaging in the United States, Western Europe, and
Japan.

Despite its prevalence in the environment, no living organism is known
to metabolize aluminium salts, but this aluminium is well tolerated by
plants and animals. Because of the abundance of these salts, the
potential for a biological role for them is of interest, and studies
are ongoing.


Isotopes
==========
Of aluminium isotopes, only  is stable. This situation is common for
elements with an odd atomic number. It is the only primordial
aluminium isotope, i.e. the only one that has existed on Earth in its
current form since the formation of the planet. It is therefore a
mononuclidic element and its standard atomic weight is virtually the
same as that of the isotope. This makes aluminium very useful in
nuclear magnetic resonance (NMR), as its single stable isotope has a
high NMR sensitivity. The standard atomic weight of aluminium is low
in comparison with many other metals.

All other isotopes of aluminium are radioactive. The most stable of
these is 26Al: while it was present along with stable 27Al in the
interstellar medium from which the Solar System formed, having been
produced by stellar nucleosynthesis as well, its half-life is only
717,000 years and therefore a detectable amount has not survived since
the formation of the planet. However, minute traces of 26Al are
produced from argon in the atmosphere by spallation caused by cosmic
ray protons. The ratio of 26Al to 10Be has been used for radiodating
of geological processes over 105 to 106 year time scales, in
particular transport, deposition, sediment storage, burial times, and
erosion.
Most meteorite scientists believe that the energy released by the
decay of 26Al was responsible for the melting and differentiation of
some asteroids after their formation 4.55 billion years ago.

The remaining isotopes of aluminium, with mass numbers ranging from 21
to 43, all have half-lives well under an hour. Three metastable states
are known, all with half-lives under a minute.


Electron shell
================
An aluminium atom has 13 electrons, arranged in an electron
configuration of , with three electrons beyond a stable noble gas
configuration. Accordingly, the combined first three ionization
energies of aluminium are far lower than the fourth ionization energy
alone. Such an electron configuration is shared with the other
well-characterized members of its group, boron, gallium, indium, and
thallium; it is also expected for nihonium. Aluminium can surrender
its three outermost electrons in many chemical reactions (see below).
The electronegativity of aluminium is 1.61 (Pauling scale).
A free aluminium atom has a radius of 143 pm. With the three outermost
electrons removed, the radius shrinks to 39 pm for a 4-coordinated
atom or 53.5 pm for a 6-coordinated atom. At standard temperature and
pressure, aluminium atoms (when not affected by atoms of other
elements) form a face-centered cubic crystal system bound by metallic
bonding provided by atoms' outermost electrons; hence aluminium (at
these conditions) is a metal. This crystal system is shared by many
other metals, such as lead and copper; the size of a unit cell of
aluminium is comparable to that of those other metals.
The system, however, is not shared by the other members of its group:
boron has ionization energies too high to allow metallization,
thallium has a hexagonal close-packed structure, and gallium and
indium have unusual structures that are not close-packed like those of
aluminium and thallium. The few electrons that are available for
metallic bonding in aluminium are a probable cause for it being soft
with a low melting point and low electrical resistivity.


Bulk
======
Aluminium metal has an appearance ranging from silvery white to dull
gray depending on its surface roughness. Aluminium mirrors provides
high reflectivity for light in the ultraviolet, visible (on par with
silver), and the far infrared region. Aluminium is also good at
reflecting solar radiation, although prolonged exposure to sunlight in
air can deteriorate the reflectivity of the metal; this may be
prevented if aluminium is anodized, which adds a protective layer of
oxide on the surface.

The density of aluminium is 2.70 g/cm3, about 1/3 that of steel, much
lower than other commonly encountered metals, making aluminium parts
easily identifiable through their lightness. Aluminium's low density
compared to most other metals arises from the fact that its nuclei are
much lighter, while difference in the unit cell size does not
compensate for this difference. The only lighter metals are the metals
of groups 1 and 2, which apart from beryllium and magnesium are too
reactive for structural use (and beryllium is very toxic).
Aluminium is not as strong or stiff as steel, but the low density
makes up for this in the aerospace industry and for many other
applications where light weight and relatively high strength are
crucial.

Pure aluminium is quite soft and lacking in strength. In most
applications various aluminium alloys are used instead because of
their higher strength and hardness. The yield strength of pure
aluminium is 7-11 MPa, while aluminium alloys have yield strengths
ranging from 200 MPa to 600 MPa.
Aluminium is ductile, with a percent elongation of 50-70%,
and malleable allowing it to be easily drawn and extruded. It is also
easily machined and cast.

Aluminium is an excellent thermal and electrical conductor, having
around 60% the conductivity of copper, both thermal and electrical,
while having only 30% of copper's density. Aluminium is capable of
superconductivity, with a superconducting critical temperature of 1.2
kelvin and a critical magnetic field of about 100 gauss (10
milliteslas).
It is paramagnetic and thus essentially unaffected by static magnetic
fields. The high electrical conductivity, however, means that it is
strongly affected by alternating magnetic fields through the induction
of eddy currents.


                             Chemistry
======================================================================
Aluminium combines characteristics of pre- and post-transition metals.
Since it has few available electrons for metallic bonding, like its
heavier group 13 congeners, it has the characteristic physical
properties of a post-transition metal, with longer-than-expected
interatomic distances. Furthermore, as Al3+ is a small and highly
charged cation, it is strongly polarizing and bonding in aluminium
compounds tends towards covalency; this behavior is similar to that of
beryllium (Be2+), and the two display an example of a diagonal
relationship.

The underlying core under aluminium's valence shell is that of the
preceding noble gas, whereas those of its heavier congeners gallium,
indium, thallium, and nihonium also include a filled d-subshell and in
some cases a filled f-subshell. Hence, the inner electrons of
aluminium shield the valence electrons almost completely, unlike those
of aluminium's heavier congeners. As such, aluminium is the most
electropositive metal in its group, and its hydroxide is in fact more
basic than that of gallium. Aluminium also bears minor similarities to
the metalloid boron in the same group: AlX3 compounds are valence
isoelectronic to BX3 compounds (they have the same valence electronic
structure), and both behave as Lewis acids and readily form adducts.
Additionally, one of the main motifs of boron chemistry is regular
icosahedral structures, and aluminium forms an important part of many
icosahedral quasicrystal alloys, including the Al-Zn-Mg class.

Aluminium has a high chemical affinity to oxygen, which renders it
suitable for use as a reducing agent in the thermite reaction. A fine
powder of aluminium reacts explosively on contact with liquid oxygen;
under normal conditions, however, aluminium forms a thin oxide layer
(~5 nm at room temperature)
that protects the metal from further corrosion by oxygen, water, or
dilute acid, a process termed passivation.
Aluminium is not attacked by oxidizing acids because of its
passivation. This allows aluminium to be used to store reagents such
as nitric acid, concentrated sulfuric acid, and some organic acids.

In hot concentrated hydrochloric acid, aluminium reacts with water
with evolution of hydrogen, and in aqueous sodium hydroxide or
potassium hydroxide at room temperature to form aluminates--protective
passivation under these conditions is negligible. Aqua regia also
dissolves aluminium. Aluminium is corroded by dissolved chlorides,
such as common sodium chloride. The oxide layer on aluminium is also
destroyed by contact with mercury due to amalgamation or with salts of
some electropositive metals. As such, the strongest aluminium alloys
are less corrosion-resistant due to galvanic reactions with alloyed
copper, and aluminium's corrosion resistance is greatly reduced by
aqueous salts, particularly in the presence of dissimilar metals.

Aluminium reacts with most nonmetals upon heating, forming compounds
such as aluminium nitride (AlN), aluminium sulfide (Al2S3), and the
aluminium halides (AlX3). It also forms a wide range of intermetallic
compounds involving metals from every group on the periodic table.


Inorganic compounds
=====================
The vast majority of compounds, including all aluminium-containing
minerals and all commercially significant aluminium compounds, feature
aluminium in the oxidation state 3+. The coordination number of such
compounds varies, but generally Al3+ is either six- or
four-coordinate. Almost all compounds of aluminium(III) are colorless.

|last1=Baes|first1=C. F. |last2=Mesmer|first2=R. E.
|title=The Hydrolysis of Cations|year=1986|orig-year=1976
In aqueous solution, Al3+ exists as the hexaaqua cation [Al(H2O)6]3+,
which has an approximate Ka of 10−5. Such solutions are acidic as this
cation can act as a proton donor and progressively hydrolyze until a
precipitate of aluminium hydroxide, Al(OH)3, forms. This is useful for
clarification of water, as the precipitate nucleates on suspended
particles in the water, hence removing them. Increasing the pH even
further leads to the hydroxide dissolving again as aluminate,
[Al(H2O)2(OH)4]−, is formed.

Aluminium hydroxide forms both salts and aluminates and dissolves in
acid and alkali, as well as on fusion with acidic and basic oxides.
This behavior of Al(OH)3 is termed amphoterism and is characteristic
of weakly basic cations that form insoluble hydroxides and whose
hydrated species can also donate their protons. One effect of this is
that aluminium salts with weak acids are hydrolyzed in water to the
aquated hydroxide and the corresponding nonmetal hydride: for example,
aluminium sulfide yields hydrogen sulfide. However, some salts like
aluminium carbonate exist in aqueous solution but are unstable as
such; and only incomplete hydrolysis takes place for salts with strong
acids, such as the halides, nitrate, and sulfate. For similar reasons,
anhydrous aluminium salts cannot be made by heating their "hydrates":
hydrated aluminium chloride is in fact not AlCl3·6H2O but
[Al(H2O)6]Cl3, and the Al-O bonds are so strong that heating is not
sufficient to break them and form Al-Cl bonds. This reaction is
observed instead:

:2[Al(H2O)6]Cl3  Al2O3 + 6 HCl + 9 H2O

All four trihalides are well known. Unlike the structures of the three
heavier trihalides, aluminium fluoride (AlF3) features six-coordinate
aluminium, which explains its involatility and insolubility as well as
high heat of formation. Each aluminium atom is surrounded by six
fluorine atoms in a distorted octahedral arrangement, with each
fluorine atom being shared between the corners of two octahedra. Such
{AlF6} units also exist in complex fluorides such as cryolite,
Na3AlF6. AlF3 melts at 1290 °C and is made by reaction of aluminium
oxide with hydrogen fluoride gas at 700 °C.

With heavier halides, the coordination numbers are lower. The other
trihalides are dimeric or polymeric with tetrahedral four-coordinate
aluminium centers. Aluminium trichloride (AlCl3) has a layered
polymeric structure below its melting point of 192.4 °C but transforms
on melting to Al2Cl6 dimers. At higher temperatures those increasingly
dissociate into trigonal planar AlCl3 monomers similar to the
structure of BCl3. Aluminium tribromide and aluminium triiodide form
Al2X6 dimers in all three phases and hence do not show such
significant changes of properties upon phase change. These materials
are prepared by treating aluminium with the halogen. The aluminium
trihalides form many addition compounds or complexes; their Lewis
acidic nature makes them useful as catalysts for the Friedel-Crafts
reactions. Aluminium trichloride has major industrial uses involving
this reaction, such as in the manufacture of anthraquinones and
styrene; it is also often used as the precursor for many other
aluminium compounds and as a reagent for converting nonmetal fluorides
into the corresponding chlorides (a transhalogenation reaction).

Aluminium forms one stable oxide with the chemical formula Al2O3,
commonly called alumina.
It can be found in nature in the mineral corundum, α-alumina;
there is also a γ-alumina phase. Its crystalline form, corundum, is
very hard (Mohs hardness 9), has a high melting point of 2045 °C, has
very low volatility, is chemically inert, and a good electrical
insulator, it is often used in abrasives (such as toothpaste), as a
refractory material, and in ceramics, as well as being the starting
material for the electrolytic production of aluminium. Sapphire and
ruby are impure corundum contaminated with trace amounts of other
metals. The two main oxide-hydroxides, AlO(OH), are boehmite and
diaspore. There are three main trihydroxides: bayerite, gibbsite, and
nordstrandite, which differ in their crystalline structure
(polymorphs). Many other intermediate and related structures are also
known. Most are produced from ores by a variety of wet processes using
acid and base. Heating the hydroxides leads to formation of corundum.
These materials are of central importance to the production of
aluminium and are themselves extremely useful. Some mixed oxide phases
are also very useful, such as spinel (MgAl2O4), Na-β-alumina
(NaAl11O17), and tricalcium aluminate (Ca3Al2O6, an important mineral
phase in Portland cement).

The only stable chalcogenides under normal conditions are aluminium
sulfide (Al2S3), selenide (Al2Se3), and telluride (Al2Te3). All three
are prepared by direct reaction of their elements at about 1000 °C and
quickly hydrolyze completely in water to yield aluminium hydroxide and
the respective hydrogen chalcogenide. As aluminium is a small atom
relative to these chalcogens, these have four-coordinate tetrahedral
aluminium with various polymorphs having structures related to
wurtzite, with two-thirds of the possible metal sites occupied either
in an orderly (α) or random (β) fashion; the sulfide also has a γ form
related to γ-alumina, and an unusual high-temperature hexagonal form
where half the aluminium atoms have tetrahedral four-coordination and
the other half have trigonal bipyramidal five-coordination.

Four pnictides - aluminium nitride (AlN), aluminium phosphide (AlP),
aluminium arsenide (AlAs), and aluminium antimonide (AlSb) - are
known. They are all III-V semiconductors isoelectronic to silicon and
germanium, all of which but AlN have the zinc blende structure. All
four can be made by high-temperature (and possibly high-pressure)
direct reaction of their component elements.


Aluminium alloys well with most other metals (with the exception of
most alkali metals and group 13 metals) and over 150 intermetallics
with other metals are known. Preparation involves heating fixed metals
together in certain proportion, followed by gradual cooling and
annealing. Bonding in them is predominantly metallic and the crystal
structure primarily depends on efficiency of packing.

There are few compounds with lower oxidation states. A few
aluminium(I) compounds exist: AlF, AlCl, AlBr, and AlI exist in the
gaseous phase when the respective trihalide is heated with aluminium,
and at cryogenic temperatures. A stable derivative of aluminium
monoiodide is the cyclic adduct formed with triethylamine,
Al4I4(NEt3)4. Al2O and Al2S also exist but are very unstable. Very
simple aluminium(II) compounds are invoked or observed in the
reactions of Al metal with oxidants. For example, aluminium monoxide,
AlO, has been detected in the gas phase after explosion and in stellar
absorption spectra. More thoroughly investigated are compounds of the
formula R4Al2 which contain an Al-Al bond and where R is a large
organic ligand.


Organoaluminium compounds and related hydrides
================================================
A variety of compounds of empirical formula AlR3 and AlR1.5Cl1.5
exist. The aluminium trialkyls and triaryls are reactive, volatile,
and colorless liquids or low-melting solids. They catch fire
spontaneously in air and react with water, thus necessitating
precautions when handling them. They often form dimers, unlike their
boron analogues, but this tendency diminishes for branched-chain
alkyls (e.g. Pr'i', Bu'i', Me3CCH2); for example, triisobutylaluminium
exists as an equilibrium mixture of the monomer and dimer.
These dimers, such as trimethylaluminium (Al2Me6), usually feature
tetrahedral Al centers formed by dimerization with some alkyl group
bridging between both aluminium atoms. They are hard acids and react
readily with ligands, forming adducts. In industry, they are mostly
used in alkene insertion reactions, as discovered by Karl Ziegler,
most importantly in "growth reactions" that form long-chain unbranched
primary alkenes and alcohols, and in the low-pressure polymerization
of ethene and propene. There are also some heterocyclic and cluster
organoaluminium compounds involving Al-N bonds.

The industrially most important aluminium hydride is lithium aluminium
hydride (LiAlH4), which is used as a reducing agent in organic
chemistry. It can be produced from lithium hydride and aluminium
trichloride. The simplest hydride, aluminium hydride or alane, is not
as important. It is a polymer with the formula (AlH3)'n', in contrast
to the corresponding boron hydride that is a dimer with the formula
(BH3)2.


Space
=======
Aluminium's per-particle abundance in the Solar System is 3.15 ppm
(parts per million).
It is the twelfth most abundant of all elements and third most
abundant among the elements that have odd atomic numbers, after
hydrogen and nitrogen. The only stable isotope of aluminium, 27Al, is
the eighteenth most abundant nucleus in the universe. It is created
almost entirely after fusion of carbon in massive stars that will
later become Type II supernovas: this fusion creates 26Mg, which upon
capturing free protons and neutrons, becomes aluminium. Some smaller
quantities of 27Al are created in hydrogen burning shells of evolved
stars, where 26Mg can capture free protons. Essentially all aluminium
now in existence is 27Al. 26Al was present in the early Solar System
with abundance of 0.005% relative to 27Al but its half-life of 728,000
years is too short for any original nuclei to survive; 26Al is
therefore extinct. Unlike for 27Al, hydrogen burning is the primary
source of 26Al, with the nuclide emerging after a nucleus of 25Mg
catches a free proton. However, the trace quantities of 26Al that do
exist are the most common gamma ray emitter in the interstellar gas;
if the original 26Al were still present, gamma ray maps of the Milky
Way would be brighter.


Earth
=======
Overall, the Earth is about 1.59% aluminium by mass (seventh in
abundance by mass). Aluminium occurs in greater proportion in the
Earth's crust than in the universe at large. This is because aluminium
easily forms the oxide and becomes bound into rocks and stays in the
Earth's crust, while less reactive metals sink to the core. In the
Earth's crust, aluminium is the most abundant metallic element (8.23%
by mass) and the third most abundant of all elements (after oxygen and
silicon). A large number of silicates in the Earth's crust contain
aluminium. In contrast, the Earth's mantle is only 2.38% aluminium by
mass. Aluminium also occurs in seawater at a concentration of 0.41
μg/kg.

Because of its strong affinity for oxygen, aluminium is almost never
found in the elemental state; instead it is found in oxides or
silicates. Feldspars, the most common group of minerals in the Earth's
crust, are aluminosilicates. Aluminium also occurs in the minerals
beryl, cryolite, garnet, spinel, and turquoise. Impurities in Al2O3,
such as chromium and iron, yield the gemstones ruby and sapphire,
respectively. Native aluminium metal is extremely rare and can only be
found as a minor phase in low oxygen fugacity environments, such as
the interiors of certain volcanoes. Native aluminium has been reported
in cold seeps in the northeastern continental slope of the South China
Sea. It is possible that these deposits resulted from bacterial
reduction of tetrahydroxoaluminate Al(OH)4−.

Although aluminium is a common and widespread element, not all
aluminium minerals are economically viable sources of the metal.
Almost all metallic aluminium is produced from the ore bauxite
(AlO'x'(OH)3-2'x'). Bauxite occurs as a weathering product of low iron
and silica bedrock in tropical climatic conditions. In 2017, most
bauxite was mined in Australia, China, Guinea, and India.


                              History
======================================================================
The history of aluminium has been shaped by usage of alum. The first
written record of alum, made by Greek historian Herodotus, dates back
to the 5th century BCE. The ancients are known to have used alum as a
dyeing mordant and for city defense. After the Crusades, alum, an
indispensable good in the European fabric industry, was a subject of
international commerce; it was imported to Europe from the eastern
Mediterranean until the mid-15th century.

The nature of alum remained unknown. Around 1530, Swiss physician
Paracelsus suggested alum was a salt of an earth of alum. In 1595,
German doctor and chemist Andreas Libavius experimentally confirmed
this. In 1722, German chemist Friedrich Hoffmann announced his belief
that the base of alum was a distinct earth. In 1754, German chemist
Andreas Sigismund Marggraf synthesized alumina by boiling clay in
sulfuric acid and subsequently adding potash.

Attempts to produce aluminium date back to 1760. The first successful
attempt, however, was completed in 1824 by Danish physicist and
chemist Hans Christian Ørsted. He reacted anhydrous aluminium chloride
with potassium amalgam, yielding a lump of metal looking similar to
tin. He presented his results and demonstrated a sample of the new
metal in 1825. In 1827, German chemist Friedrich Wöhler repeated
Ørsted's experiments but did not identify any aluminium. (The reason
for this inconsistency was only discovered in 1921.) He conducted a
similar experiment in the same year by mixing anhydrous aluminium
chloride with potassium (the Wöhler process) and produced a powder of
aluminium. In 1845, he was able to produce small pieces of the metal
and described some physical properties of this metal. For many years
thereafter, Wöhler was credited as the discoverer of aluminium.


As Wöhler's method could not yield great quantities of aluminium, the
metal remained rare; its cost exceeded that of gold. The first
industrial production of aluminium was established in 1856 by French
chemist Henri Etienne Sainte-Claire Deville and companions. Deville
had discovered that aluminium trichloride could be reduced by sodium,
which was more convenient and less expensive than potassium, which
Wöhler had used. Even then, aluminium was still not of great purity
and produced aluminium differed in properties by sample. Because of
its electricity-conducting capacity, aluminium was used as the cap of
the Washington Monument, completed in 1885, the tallest building in
the world at the time.  The non-corroding metal cap was intended to
serve as a lightning rod peak.

The first industrial large-scale production method was independently
developed in 1886 by French engineer Paul Héroult and American
engineer Charles Martin Hall; it is now known as the Hall-Héroult
process. The Hall-Héroult process converts alumina into metal.
Austrian chemist Carl Joseph Bayer discovered a way of purifying
bauxite to yield alumina, now known as the Bayer process, in 1889.
Modern production of aluminium is based on the Bayer and Hall-Héroult
processes.

As large-scale production caused aluminium prices to drop, the metal
became widely used in jewelry, eyeglass frames, optical instruments,
tableware, and foil, and other everyday items in the 1890s and early
20th century. Aluminium's ability to form hard yet light alloys with
other metals provided the metal with many uses at the time. During
World War I, major governments demanded large shipments of aluminium
for light strong airframes;
during World War II, demand by major governments for aviation was
even higher.

From the early 20th century to 1980, the aluminium industry was
characterized by cartelization, as aluminium firms colluded to keep
prices high and stable. The first aluminium cartel, the Aluminium
Association, was founded in 1901 by the Pittsburgh Reduction Company
(renamed Alcoa in 1907) and Aluminium Industrie AG. The British
Aluminium Company, Produits Chimiques d’Alais et de la Camargue, and
Société Electro-Métallurgique de Froges also joined the cartel.

By the mid-20th century, aluminium had become a part of everyday life
and an essential component of housewares. In 1954, production of
aluminium surpassed that of copper, historically second in production
only to iron, making it the most produced non-ferrous metal. During
the mid-20th century, aluminium emerged as a civil engineering
material, with building applications in both basic construction and
interior finish work, and increasingly being used in military
engineering, for both airplanes and land armor vehicle engines.
Earth's first artificial satellite, launched in 1957, consisted of two
separate aluminium semi-spheres joined and all subsequent space
vehicles have used aluminium to some extent. The aluminium can was
invented in 1956 and employed as a storage for drinks in 1958.


Throughout the 20th century, the production of aluminium rose rapidly:
while the world production of aluminium in 1900 was 6,800 metric tons,
the annual production first exceeded 100,000 metric tons in 1916;
1,000,000 tons in 1941; 10,000,000 tons in 1971. In the 1970s, the
increased demand for aluminium made it an exchange commodity; it
entered the London Metal Exchange, the oldest industrial metal
exchange in the world, in 1978. The output continued to grow: the
annual production of aluminium exceeded 50,000,000 metric tons in
2013.

The real price for aluminium declined from $14,000 per metric ton in
1900 to $2,340 in 1948 (in 1998 United States dollars). Extraction and
processing costs were lowered over technological progress and the
scale of the economies. However, the need to exploit lower-grade
poorer quality deposits and the use of fast increasing input costs
(above all, energy) increased the net cost of aluminium; the real
price began to grow in the 1970s with the rise of energy cost.
Production moved from the industrialized countries to countries where
production was cheaper. Production costs in the late 20th century
changed because of advances in technology, lower energy prices,
exchange rates of the United States dollar, and alumina prices. The
BRIC countries' combined share in primary production and primary
consumption grew substantially in the first decade of the 21st
century. China is accumulating an especially large share of the
world's production thanks to an abundance of resources, cheap energy,
and governmental stimuli; it also increased its consumption share from
2% in 1972 to 40% in 2010. In the United States, Western Europe, and
Japan, most aluminium was consumed in transportation, engineering,
construction, and packaging. In 2021, prices for industrial metals
such as aluminium have soared to near-record levels as energy
shortages in China drive up costs for electricity.


                             Etymology
======================================================================
The names 'aluminium' and 'aluminum' are derived from the word
'alumine', an obsolete term for 'alumina', the primary naturally
occurring oxide of aluminium.
'Alumine' was borrowed from French, which in turn derived it from
'alumen', the classical Latin name for alum, the mineral from which it
was collected.
The Latin word 'alumen' stems from the Proto-Indo-European root
'*alu-' meaning "bitter" or "beer".


Origins
=========
British chemist Humphry Davy, who performed a number of experiments
aimed to isolate the metal, is credited as the person who named the
element. The first name proposed for the metal to be isolated from
alum was 'alumium', which Davy suggested in an 1808 article on his
electrochemical research, published in Philosophical Transactions of
the Royal Society. It appeared that the name was created from the
English word 'alum' and the Latin suffix '-ium'; but it was customary
then to give elements names originating in Latin, so this name was not
adopted universally. This name was criticized by contemporary chemists
from France, Germany, and Sweden, who insisted the metal should be
named for the oxide, alumina, from which it would be isolated. The
English name 'alum' does not come directly from Latin, whereas
'alumine'/'alumina' comes from the Latin word 'alumen' (upon
declension, 'alumen' changes to 'alumin-').

One example was 'Essai sur la Nomenclature chimique' (July 1811),
written in French by a Swedish chemist, Jöns Jacob Berzelius, in which
the name 'aluminium' is given to the element that would be synthesized
from alum. (Another article in the same journal issue also refers to
the metal whose oxide is the basis of sapphire, i.e. the same metal,
as to 'aluminium'.) A January 1811 summary of one of Davy's lectures
at the Royal Society mentioned the name 'aluminium' as a possibility.
The next year, Davy published a chemistry textbook in which he used
the spelling 'aluminum'. Both spellings have coexisted since. Their
usage is currently regional: 'aluminum' dominates in the United States
and Canada; 'aluminium' is prevalent in the rest of the
English-speaking world.


Spelling
==========
In 1812, British scientist Thomas Young wrote an anonymous review of
Davy's book, in which he proposed the name 'aluminium' instead of
'aluminum', which he thought had a "less classical sound". This name
persisted: although the ' spelling was occasionally used in Britain,
the American scientific language used ' from the start.

Ludwig Wilhelm Gilbert had proposed 'Thonerde-metall', after the
German "Thonerde" for alumina, in his 'Annalen der Physik' but that
name never caught on at all even in Germany.  Joseph W. Richards in
1891 found just one occurrence of 'argillium' in Swedish, from the
French "argille" for clay.  The French themselves had used 'aluminium'
from the start. However, in England and Germany Davy's spelling
'aluminum' was initially used; until German chemist Friedrich Wöhler
published his account of the Wöhler process in 1827 in which he used
the spelling 'aluminium', which caused that spelling's largely
wholesale adoption in England and Germany, with the exception of a
small number of what Richards characterized as "patriotic" English
chemists that were "averse to foreign innovations" who occasionally
still used 'aluminum'.

Most scientists throughout the world used ' in the 19th century; and
it was entrenched in several other European languages, such as French,
German, and Dutch.

In 1828, an American lexicographer, Noah Webster, entered only the
'aluminum' spelling in his 'American Dictionary of the English
Language'. In the 1830s, the ' spelling gained usage in the United
States; by the 1860s, it had become the more common spelling there
outside science. In 1892, Hall used the ' spelling in his advertising
handbill for his new electrolytic method of producing the metal,
despite his constant use of the ' spelling in all the patents he filed
between 1886 and 1903. It is unknown whether this spelling was
introduced by mistake or intentionally, but Hall preferred 'aluminum'
since its introduction because it resembled 'platinum', the name of a
prestigious metal. By 1890, both spellings had been common in the
United States, the ' spelling being slightly more common; by 1895, the
situation had reversed; by 1900, 'aluminum' had become twice as common
as 'aluminium'; in the next decade, the ' spelling dominated American
usage. In 1925, the American Chemical Society adopted this spelling.

The International Union of Pure and Applied Chemistry (IUPAC) adopted
'aluminium' as the standard international name for the element in
1990. In 1993, they recognized 'aluminum' as an acceptable variant;
the most recent 2005 edition of the IUPAC nomenclature of inorganic
chemistry also acknowledges this spelling. IUPAC official publications
use the ' spelling as primary, and they list both where it is
appropriate.


                     Production and refinement
======================================================================
(thousand  tons)
align="right"|43,000
align="right"|4,200
align="right"|3,800
align="right"|3,300
align="right"|2,700
align="right"|1,600
align="right"|1,500
align="right"|1,300
align="right"|1,100
align="right"|870
align="right"|780
align="right"|670
Other countries          align="right"|6,800
Total    align="right"|72,000


The production of aluminium starts with the extraction of bauxite rock
from the ground. The bauxite is processed and transformed using the
Bayer process into alumina, which is then processed using the
Hall-Héroult process, resulting in the final aluminium.

Aluminium production is highly energy-consuming, and so the producers
tend to locate smelters in places where electric power is both
plentiful and inexpensive. Production of one kilogram of aluminium
requires 7 kilograms of oil energy equivalent, as compared to 1.5
kilograms for steel and 2 kilograms for plastic. As of 2024, the
world's largest producers of aluminium were China, Russia, India,
Canada, and the United Arab Emirates, while China is by far the top
producer of aluminium with a world share of over 55%.

According to the International Resource Panel's Metal Stocks in
Society report, the global per capita stock of aluminium in use in
society (i.e. in cars, buildings, electronics, etc.) is 80 kg. Much of
this is in more-developed countries (350 - per capita) rather than
less-developed countries (35 kg per capita).


Bayer process
===============
Bauxite is converted to alumina by the Bayer process. Bauxite is
blended for uniform composition and then is ground fine. The resulting
slurry is mixed with a hot solution of sodium hydroxide; the mixture
is then treated in a digester vessel at a pressure well above
atmospheric, dissolving the aluminium hydroxide in bauxite while
converting impurities into relatively insoluble compounds:



After this reaction, the slurry is at a temperature above its
atmospheric boiling point. It is cooled by removing steam as pressure
is reduced. The bauxite residue is separated from the solution and
discarded. The solution, free of solids, is seeded with small crystals
of aluminium hydroxide; this causes decomposition of the [Al(OH)4]−
ions to aluminium hydroxide. After about half of aluminium has
precipitated, the mixture is sent to classifiers. Small crystals of
aluminium hydroxide are collected to serve as seeding agents; coarse
particles are converted to alumina by heating; the excess solution is
removed by evaporation, (if needed) purified, and recycled.


Hall–Héroult process
======================
The conversion of alumina to aluminium is achieved by the Hall-Héroult
process. In this energy-intensive process, a solution of alumina in a
molten (940 and) mixture of cryolite (Na3AlF6) with calcium fluoride
is electrolyzed to produce metallic aluminium. The liquid aluminium
sinks to the bottom of the solution and is tapped off, and usually
cast into large blocks called aluminium billets for further
processing.

Anodes of the electrolysis cell are made of carbon--the most resistant
material against fluoride corrosion--and either bake at the process or
are prebaked. The former, also called Söderberg anodes, are less
power-efficient and fumes released during baking are costly to
collect, which is why they are being replaced by prebaked anodes even
though they save the power, energy, and labor to prebake the cathodes.
Carbon for anodes should be preferably pure so that neither aluminium
nor the electrolyte is contaminated with ash. Despite carbon's
resistivity against corrosion, it is still consumed at a rate of
0.4-0.5 kg per each kilogram of produced aluminium. Cathodes are made
of anthracite; high purity for them is not required because impurities
leach only very slowly. The cathode is consumed at a rate of 0.02-0.04
kg per each kilogram of produced aluminium. A cell is usually
terminated after 2-6 years following a failure of the cathode.

The Hall-Heroult process produces aluminium with a purity of above
99%. Further purification can be done by the Hoopes process. This
process involves the electrolysis of molten aluminium with a sodium,
barium, and aluminium fluoride electrolyte. The resulting aluminium
has a purity of 99.99%.

Electric power represents about 20 to 40% of the cost of producing
aluminium, depending on the location of the smelter. Aluminium
production consumes roughly 5% of electricity generated in the United
States. Because of this, alternatives to the Hall-Héroult process have
been researched, but none has turned out to be economically feasible.


Recycling
===========
Recovery of the metal through recycling has become an important task
of the aluminium industry. Recycling was a low-profile activity until
the late 1960s, when the growing use of aluminium beverage cans
brought it to public awareness. Recycling involves melting the scrap,
a process that requires only 5% of the energy used to produce
aluminium from ore, though a significant part (up to 15% of the input
material) is lost as dross (ash-like oxide). An aluminium stack melter
produces significantly less dross, with values reported below 1%.

White dross from primary aluminium production and from secondary
recycling operations still contains useful quantities of aluminium
that can be extracted industrially. The process produces aluminium
billets, together with a highly complex waste material. This waste is
difficult to manage. It reacts with water, releasing a mixture of
gases including, among others, acetylene, hydrogen sulfide and
significant amounts of ammonia. Despite these difficulties, the waste
is used as a filler in asphalt and concrete. Its potential for
hydrogen production has also been considered and researched.


Metal
=======
The global production of aluminium in 2016 was 58.8 million metric
tons. It exceeded that of any other metal except iron (1,231 million
metric tons).

Aluminium is almost always alloyed, which markedly improves its
mechanical properties, especially when tempered. For example, the
common aluminium foils and beverage cans are alloys of 92% to 99%
aluminium. The main alloying agents for both wrought and cast
aluminium are copper, zinc, magnesium, manganese, and silicon (e.g.,
duralumin) with the levels of other metals in a few percent by weight.


The major uses for aluminium are in:
* Transportation (automobiles, aircraft, trucks, railway cars, marine
vessels, bicycles, spacecraft, 'etc.'). Aluminium is used because of
its low density;
* Packaging (cans, foil, frame, etc.). Aluminium is used because it is
non-toxic (see below), non-adsorptive, and splinter-proof;
* Building and construction (windows, doors, siding, building wire,
sheathing, roofing, 'etc.'). Since steel is cheaper, aluminium is used
when lightness, corrosion resistance, or engineering features are
important;
* Electricity-related uses (conductor alloys, motors, and generators,
transformers, capacitors, 'etc.'). Aluminium is used because it is
relatively cheap, highly conductive, has adequate mechanical strength
and low density, and resists corrosion;
* A wide range of household items, from cooking utensils to furniture.
Low density, good appearance, ease of fabrication, and durability are
the key factors of aluminium usage;
* Machinery and equipment (processing equipment, pipes, tools).
Aluminium is used because of its corrosion resistance,
non-pyrophoricity, and mechanical strength.


Compounds
===========
The great majority (about 90%) of aluminium oxide is converted to
metallic aluminium. Being a very hard material (Mohs hardness 9),
alumina is widely used as an abrasive; being extraordinarily
chemically inert, it is useful in highly reactive environments such as
high pressure sodium lamps. Aluminium oxide is commonly used as a
catalyst for industrial processes; e.g. the Claus process to convert
hydrogen sulfide to sulfur in refineries and to alkylate amines. Many
industrial catalysts are supported by alumina, meaning that the
expensive catalyst material is dispersed over a surface of the inert
alumina. Another principal use is as a drying agent or absorbent.

Several sulfates of aluminium have industrial and commercial
application. Aluminium sulfate (in its hydrate form) is produced on
the annual scale of several millions of metric tons. About two-thirds
is consumed in water treatment. The next major application is in the
manufacture of paper. It is also used as a mordant in dyeing, in
pickling seeds, deodorizing of mineral oils, in leather tanning, and
in production of other aluminium compounds. Two kinds of alum,
ammonium alum and potassium alum, were formerly used as mordants and
in leather tanning, but their use has significantly declined following
availability of high-purity aluminium sulfate. Anhydrous aluminium
chloride is used as a catalyst in chemical and petrochemical
industries, the dyeing industry, and in synthesis of various inorganic
and organic compounds. Aluminium hydroxychlorides are used in
purifying water, in the paper industry, and as antiperspirants. Sodium
aluminate is used in treating water and as an accelerator of
solidification of cement.

Many aluminium compounds have niche applications, for example:
* Aluminium acetate in solution is used as an astringent.
* Aluminium phosphate is used in the manufacture of glass, ceramic,
pulp and paper products, cosmetics, paints, varnishes, and in dental
cement.
* Aluminium hydroxide is used as an antacid, and mordant; it is used
also in water purification, the manufacture of glass and ceramics, and
in the waterproofing of fabrics.
* Lithium aluminium hydride is a powerful reducing agent used in
organic chemistry.
* Organoaluminiums are used as Lewis acids and co-catalysts.
* Methylaluminoxane is a co-catalyst for Ziegler-Natta olefin
polymerization to produce vinyl polymers such as polyethene.
* Aqueous aluminium ions (such as aqueous aluminium sulfate) are used
to treat against fish parasites such as 'Gyrodactylus salaris'.
* In many vaccines, certain aluminium salts serve as an immune
adjuvant (immune response booster) to allow the protein in the vaccine
to achieve sufficient potency as an immune stimulant. Until 2004, most
of the adjuvants used in vaccines were aluminium-adjuvanted.


                              Biology
======================================================================
Despite its widespread occurrence in the Earth's crust, aluminium has
no known function in biology. At pH 6-9 (relevant for most natural
waters), aluminium precipitates out of water as the hydroxide and is
hence not available; most elements behaving this way have no
biological role or are toxic. Aluminium sulfate has an LD50 of 6207
mg/kg (oral, mouse), which corresponds to 435 grams (about one pound)
for a 70 kg mouse.


Toxicity
==========
Aluminium is classified as a non-carcinogen by the United States
Department of Health and Human Services. A review published in 1988
said that there was little evidence that normal exposure to aluminium
presents a risk to healthy adult, and a 2014 multi-element toxicology
review was unable to find deleterious effects of aluminium consumed in
amounts not greater than 40 mg/day per kg of body mass. Most aluminium
consumed will leave the body in feces; most of the small part of it
that enters the bloodstream, will be excreted via urine; nevertheless
some aluminium does pass the blood-brain barrier and is lodged
preferentially in the brains of Alzheimer's patients.
Evidence published in 1989 indicates that, for Alzheimer's patients,
aluminium may act by electrostatically crosslinking proteins, thus
down-regulating genes in the superior temporal gyrus.


Effects
=========
Aluminium, although rarely, can cause vitamin D-resistant
osteomalacia, erythropoietin-resistant microcytic anemia, and central
nervous system alterations. People with kidney insufficiency are
especially at a risk. Chronic ingestion of hydrated aluminium
silicates (for excess gastric acidity control) may result in aluminium
binding to intestinal contents and increased elimination of other
metals, such as iron or zinc; sufficiently high doses (>50 g/day)
can cause anemia.


During the 1988 Camelford water pollution incident, people in
Camelford had their drinking water contaminated with aluminium sulfate
for several weeks. A final report into the incident in 2013 concluded
it was unlikely that this had caused long-term health problems.

Aluminium has been suspected of being a possible cause of Alzheimer's
disease, but research into this for over 40 years has found, , no good
evidence of causal effect.


Aluminium increases estrogen-related gene expression in human breast
cancer cells cultured in the laboratory.
In very high doses, aluminium is associated with altered function of
the blood-brain barrier.
A small percentage of people have contact allergies to aluminium and
experience itchy red rashes, headache, muscle pain, joint pain, poor
memory, insomnia, depression, asthma, irritable bowel syndrome, or
other symptoms upon contact with products containing aluminium.

Exposure to powdered aluminium or aluminium welding fumes can cause
pulmonary fibrosis. Fine aluminium powder can ignite or explode,
posing another workplace hazard.


Exposure routes
=================
Food is the main source of aluminium. Drinking water contains more
aluminium than solid food; however, aluminium in food may be absorbed
more than aluminium from water. Major sources of human oral exposure
to aluminium include food (due to its use in food additives, food and
beverage packaging, and cooking utensils), drinking water (due to its
use in municipal water treatment), and aluminium-containing
medications (particularly antacid/antiulcer and buffered aspirin
formulations). Dietary exposure in Europeans averages to 0.2-1.5
mg/kg/week but can be as high as 2.3 mg/kg/week. Higher exposure
levels of aluminium are mostly limited to plumbers, masons, electrical
workers, machinists, and surgeons.

Consumption of antacids, antiperspirants, vaccines, and cosmetics
provide possible routes of exposure. Consumption of acidic foods or
liquids with aluminium enhances aluminium absorption, and maltol has
been shown to increase the accumulation of aluminium in nerve and bone
tissues.


Treatment
===========
In case of suspected sudden intake of a large amount of aluminium, the
only treatment is deferoxamine mesylate which may be given to help
eliminate aluminium from the body by chelation therapy. However, this
should be applied with caution as this reduces not only aluminium body
levels, but also those of other metals such as copper or iron.


                       Environmental effects
======================================================================
High levels of aluminium occur near mining sites; small amounts of
aluminium are released to the environment at coal-fired power plants
or incinerators. Aluminium in the air is washed out by the rain or
normally settles down but small particles of aluminium remain in the
air for a long time.

Acidic precipitation is the main natural factor to mobilize aluminium
from natural sources and the main reason for the environmental effects
of aluminium; however, the main factor of presence of aluminium in
salt and freshwater are the industrial processes that also release
aluminium into air.

In water, aluminium acts as a toxiс agent on gill-breathing animals
such as fish when the water is acidic, in which aluminium may
precipitate on gills, which causes loss of plasma- and hemolymph ions
leading to osmoregulatory failure. Organic complexes of aluminium may
be easily absorbed and interfere with metabolism in mammals and birds,
even though this rarely happens in practice.

Aluminium is primary among the factors that reduce plant growth on
acidic soils. Although it is generally harmless to plant growth in
pH-neutral soils, in acid soils the concentration of toxic Al3+
cations increases and disturbs root growth and function.



Wheat has developed a tolerance to aluminium, releasing organic
compounds that bind to harmful aluminium cations. Sorghum is believed
to have the same tolerance mechanism.

Aluminium production possesses its own challenges to the environment
on each step of the production process. The major challenge is the
emission of greenhouse gases. These gases result from electrical
consumption of the smelters and the byproducts of processing. The most
potent of these gases are perfluorocarbons, namely CF4 and C2F6, from
the smelting process.

Biodegradation of metallic aluminium is extremely rare; most
aluminium-corroding organisms do not directly attack or consume the
aluminium, but instead produce corrosive wastes.  The fungus
'Geotrichum candidum' can consume the aluminium in compact discs. The
bacterium 'Pseudomonas aeruginosa' and the fungus 'Cladosporium
resinae' are commonly detected in aircraft fuel tanks that use
kerosene-based fuels (not avgas), and laboratory cultures can degrade
aluminium.


                              See also
======================================================================
* Aluminium granules
* Aluminium joining
* Aluminium-air battery
* Aluminized steel, for corrosion resistance and other properties
* Aluminized screen, for display devices
* Aluminized cloth, to reflect heat
* Aluminized mylar, to reflect heat
* Panel edge staining
* Quantum clock


                          Further reading
======================================================================
* Mimi Sheller, 'Aluminum Dream: The Making of Light Modernity'.
Cambridge, Mass.: Massachusetts Institute of Technology Press, 2014.


                           External links
======================================================================
* [https://www.periodicvideos.com/videos/013.htm Aluminium] at 'The
Periodic Table of Videos' (University of Nottingham)
* [https://www.atsdr.cdc.gov/ToxProfiles/tp22.pdf Toxicological
Profile for Aluminum] (PDF) (September 2008) - 357-page report from
the United States Department of Health and Human Services, Public
Health Service, Agency for Toxic Substances and Disease Registry
* [https://www.cdc.gov/niosh/npg/npgd0022.html Aluminum] entry (last
reviewed 30 October 2019) in the 'NIOSH Pocket Guide to Chemical
Hazards' published by the CDC's National Institute for Occupational
Safety and Health
*
[https://www.indexmundi.com/commodities/?commodity=aluminum&months=300
Current and historical prices] (1998–present) for aluminum futures on
the global commodities market
*


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