Aluminium And Lead

Aluminium is a silvery white member of the boron group of chemical elements. It has the symbol Al, and its atomic number is 13. It is not soluble in water under normal circumstances.

Aluminium is the third most abundant element (after oxygen and silicon), and the most abundant metal, in the Earth's crustSony VAIO VGN-CS33H battery. It makes up about 8% by weight of the Earth's solid surface. Aluminium metal is too reactive chemically to occur natively. Instead, it is found combined in over 270 different minerals.[4] The chief ore of aluminium is bauxite.

Aluminium is remarkable for the metal's low density and for its ability to resist corrosion due to the phenomenon of passivation. Structural components made from aluminium and its alloys are vital to the aerospace industry and are important in other areas of transportation and structural materialsSony VAIO VGN-CS33H/Z battery. The most useful compounds of aluminium, at least on a weight basis, are the oxides and sulfates.

Despite its prevalence in the environment, aluminium salts are not known to be used by any form of life. In keeping with its pervasiveness, aluminium is well tolerated by plants and animals.[5] Due to their prevalence, potential beneficial (or otherwise) biological roles of aluminium compounds are of continuing interestSony VAIO VGN-CS33H/B battery.

Characteristics

Etched surface from a high purity (99.9998%) aluminium bar, size 55×37 mm

Physical

Aluminium is a relatively soft, durable, lightweight, ductile and malleable metal with appearance ranging from silvery to dull gray, depending on the surface roughness. It is nonmagnetic and does not easily ignite. A fresh film of aluminium film serves as a good reflector (approximately 92%) of visible light and an excellent reflector (as much as 98%)Sony VAIO VGN-CS31Z/Q battery of medium and far infrared radiation. The yield strength of pure aluminium is 7–11 MPa, while aluminium alloys have yield strengths ranging from 200 MPa to 600 MPa.[6] Aluminium has about one-third the density and stiffness of steel. It is easily machined, cast, drawn and extruded.

Aluminium atoms are arranged in a face-centered cubic (fcc) structure. Aluminium has a stacking-fault energy of approximately 200 mJ/m2Sony VAIO VGN-CS31S/W battery.[7]

Aluminium is a good thermal and electrical conductor, having 59% the conductivity of copper, both thermal and electrical. Aluminium is capable of being a superconductor, with a superconducting critical temperature of 1.2 Kelvin and a critical magnetic field of about 100 gauss (10 milliteslas). Sony VAIO VGN-CS31S/V battery

Chemical

Corrosion resistance can be excellent due to a thin surface layer of aluminium oxide that forms when the metal is exposed to air, effectively preventing further oxidation. The strongest aluminium alloys are less corrosion resistant due to galvanic reactions with alloyed copper.[6] This corrosion resistance is also often greatly reduced by aqueous salts, particularly in the presence of dissimilar metalsSony VAIO VGN-CS31S/T battery.

Owing to its resistance to corrosion, aluminium is one of the few metals that retain silvery reflectance in finely powdered form, making it an important component of silver-colored paints. Aluminium mirror finish has the highest reflectance of any metal in the 200–400 nm (UV) and the 3,000–10,000 nm (far IR) regionsSony VAIO VGN-CS31S/R battery; in the 400–700 nm visible range it is slightly outperformed by tin and silver and in the 700–3000 (near IR) by silver, gold, and copper.[9]

Aluminium is oxidized by water to produce hydrogen and heat:

2 Al + 3 H2O → Al2O3 + 3H2

This conversion is of interest for the production or storage of energy. Challenges include the expenses associated with the regeneration of the Al metal. Sony VAIO VGN-CS31S/P battery

Isotopes

Main article: Isotopes of aluminium

Aluminium has many known isotopes, whose mass numbers range from 21 to 43; however, only 27Al (stable isotope) and 26Al (radioactive isotope, t1/2 = 7.2×105 y) occur naturally. 27Al has a natural abundance above 99.9%. 26Al is produced from argon in the atmosphere by spallation caused by cosmic-ray protonsSony VAIO VGN-CS28 battery. Aluminium isotopes have found practical application in dating marine sediments, manganese nodules, glacial ice, quartz in rock exposures, and meteorites. The ratio of 26Al to 10Be has been used to study the role of transport, deposition, sediment storage, burial times, and erosion on 105 to 106 year time scalesSony VAIO VGN-CS28/Q battery.[11] Cosmogenic 26Al was first applied in studies of the Moon and meteorites. Meteoroid fragments, after departure from their parent bodies, are exposed to intense cosmic-ray bombardment during their travel through space, causing substantial 26Al production. After falling to Earth, atmospheric shielding drastically reduces 26Al productionSony VAIO VGN-CS27 battery, and its decay can then be used to determine the meteorite's terrestrial age. Meteorite research has also shown that 26Al was relatively abundant at the time of formation of our planetary system. 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 agoSony VAIO VGN-CS27/W battery.[12]

Natural occurrence

See also: List of countries by bauxite production

Stable aluminium is created when hydrogen fuses with magnesium either in large stars or in supernovae.[13]

In the Earth's crust, aluminium is the most abundant (8.3% by weight) metallic element and the third most abundant of all elements (after oxygen and silicon).[14] Because of its strong affinity to oxygen, it is almost never found in the elemental stateSony VAIO VGN-CS27/R battery; instead it is found in oxides or silicates. Feldspars, the most common group of minerals in the Earth's crust, are aluminosilicates. Native aluminium metal can only be found as a minor phase in low oxygen fugacity environments, such as the interiors of certain volcanoes.[15] Native aluminium has been reported in cold seeps in the northeastern continental slope of the South China Sea and Chen et al. Sony VAIO VGN-CS27/P battery (2011)[16] have proposed a theory of its origin as resulting by reduction from tetrahydroxoaluminate Al(OH)4– to metallic aluminium by bacteria.[16]

It also occurs in the minerals beryl, cryolite, garnet, spinel and turquoise. Impurities in Al2O3, such as chromium or iron yield the gemstones ruby and sapphire, respectively.

Although aluminium is an extremely common and widespread element, the common aluminium minerals are not economic sources of the metalSony VAIO VGN-CS27/C battery. Almost all metallic aluminium is produced from the ore bauxite (AlOx(OH)3–2x). Bauxite occurs as a weathering product of low iron and silica bedrock in tropical climatic conditions.[17] Large deposits of bauxite occur in Australia, Brazil, Guinea and Jamaica and the primary mining areas for the ore are in Australia, Brazil, China, India, Guinea, Indonesia, Jamaica, Russia and SurinamSony VAIO VGN-CS26T/W battery.

Production and refinement

See also: Category:Aluminium minerals and List of countries by aluminium production

Bauxite, a major aluminium ore. The red-brown colour is due to the presence of iron minerals.

Aluminium forms strong chemical bonds with oxygen. Compared to most other metals, it is difficult to extract from ore, such as bauxite, due to the high reactivity of aluminum and the high melting point of most of its oresSony VAIO VGN-CS26T/V battery. For example, direct reduction with carbon, as is used to produce iron, is not chemically possible because aluminium is a stronger reducing agent than carbon. Indirect carbothermic reduction can be carried out using carbon and Al2O3, which forms an intermediate Al4C3 and this can further yield aluminium metal at a temperature of 1900–2000 °CSony VAIO VGN-CS26T/T battery. This process is still under development; it requires less energy and yields less CO2 than the Hall-Héroult process, the major industrial process for aluminium extraction.[18] Electrolytic smelting of alumina was originally cost-prohibitive in part because of the high melting point of alumina, or aluminium oxide, (about 2,000 °C (3,600 °F)) Sony VAIO VGN-CS26T/R battery. Many minerals, however, will dissolve into a second already molten mineral, even if the temperature of the melt is significantly lower than the melting point of the first mineral. Molten cryolite was discovered to dissolve alumina at temperatures signifcanlty lower than the melting point of pure alumina without interfering in the smelting processSony VAIO VGN-CS26T/Q battery. In the Hall-Héroult process, alumina is first dissolved into molten cryolite with calcium fluoride and then electolytically reduced to aluminium at a temperature between 950 and 980 °C (1,740 to 1,800 °F). Cryolite is a chemical compound of aluminium and sodium fluorides: (Na3AlF6). Although cryolite is found as a mineral in Greenland, its synthetic form is used in the industrySony VAIO VGN-CS26T/P battery. The aluminium oxide itself is obtained by refining bauxite in the Bayer process.

The electrolytic process replaced the Wöhler process, which involved the reduction of anhydrous aluminium chloride with potassium. Both of the electrodes used in the electrolysis of aluminium oxide are carbon. Once the refined alumina is dissolved in the electrolyte, it disassociates and its ions are free to move around. The reaction at the cathode isSony VAIO VGN-CS26T/C battery:

Al3+ + 3 e− → Al

Here the aluminium ion is being reduced. The aluminium metal then sinks to the bottom and is tapped off, usually cast into large blocks called aluminium billets for further processing.

At the anode, oxygen is formed:

2 O2− → O2 + 4 e−

To some extent, the carbon anode is consumed by subsequent reaction with oxygen to form carbon dioxide. The anodes in a reduction cell must therefore be replaced regularly, since they are consumed in the processSony VAIO VGN-CS25H battery. The cathodes do erode, mainly due to electrochemical processes and metal movement. After five to ten years, depending on the current used in the electrolysis, a cell has to be rebuilt because of cathode wear.

World production trend of aluminium

Aluminium electrolysis with the Hall-Héroult process consumes a lot of energy, but alternative processes were always found to be less viable economically and/or ecologicallySony VAIO VGN-CS25H/W battery. The worldwide average specific energy consumption is approximately 15±0.5 kilowatt-hours per kilogram of aluminium produced (52 to 56 MJ/kg). The most modern smelters achieve approximately 12.8 kW·h/kg (46.1 MJ/kg). (Compare this to the heat of reaction, 31 MJ/kg, and the Gibbs free energy of reaction, 29 MJ/kg.) Reduction line currents for older technologies are typically 100 to 200 kiloamperesSony VAIO VGN-CS25H/R battery; state-of-the-art smelters operate at about 350 kA. Trials have been reported with 500 kA cells.[citation needed]

The Hall-Heroult process produces aluminium with a purity of above 99%. Further purification can be done by the Hoope process. The process involves the electrolysis of molten aluminium with a sodium, barium and aluminium fluoride electrolyte. The resulting aluminium has a purity of 99.99%.Sony VAIO VGN-CS25H/Q battery

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 U.S.[21] Smelters tend to be situated where electric power is both plentiful and inexpensive, such as the United Arab Emirates with excess natural gas supplies and Iceland and Norway with energy generated from renewable sourcesSony VAIO VGN-CS25H/P battery. The world's largest smelters of alumina are People's Republic of China, Russia, and Quebec and British Columbia in Canada.[21][22][23]

Aluminium output in 2005

In 2005, the People's Republic of China was the top producer of aluminium with almost a one-fifth world share, followed by Russia, Canada, and the USA, reports the British Geological Survey.

Over the last 50 years, Australia has become a major producer of bauxite ore and a major producer and exporter of alumina (before being overtaken by China in 2007). Sony VAIO VGN-CS25H/C batteryAustralia produced 62 million tonnes of bauxite in 2005. The Australian deposits have some refining problems, some being high in silica, but have the advantage of being shallow and relatively easy to mine.[25]

Recycling

Aluminium recycling code

Main article: Aluminium recycling

Aluminium is theoretically 100% recyclable without any loss of its natural qualities. According to the International Resource Panel's Metal Stocks in Society report, the global per capita stock of aluminium in use in societySony VAIO VGN-CS23T/W battery (i.e. in cars, buildings, electronics etc.) is 80 kg. Much of this is in more-developed countries (350–500 kg per capita) rather than less-developed countries (35 kg per capita). Knowing the per capita stocks and their approximate lifespans is important for planning recyclingSony VAIO VGN-CS23T/Q battery.

Recovery of the metal via recycling has become an important facet 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 the 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). Sony VAIO VGN-CS23H batteryThe dross can undergo a further process to extract aluminium.

In Europe aluminium experiences high rates of recycling, ranging from 42% of beverage cans, 85% of construction materials and 95% of transport vehicles.[27]

Recycled aluminium is known as secondary aluminium, but maintains the same physical properties as primary aluminium. Secondary aluminium is produced in a wide range of formats and is employed in 80% of alloy injections. Another important use is for extrusionSony VAIO VGN-CS23H/S battery.

White dross from primary aluminium production and from secondary recycling operations still contains useful quantities of aluminium that can be extracted industrially.[28] The process produces aluminium billets, together with a highly complex waste material. This waste is difficult to manageSony VAIO VGN-CS23H/B battery. It reacts with water, releasing a mixture of gases (including, among others, hydrogen, acetylene, and ammonia), which spontaneously ignites on contact with air;[29] contact with damp air results in the release of copious quantities of ammonia gas. Despite these difficulties, the waste has found use as a filler in asphalt and concrete. Sony VAIO VGN-CS23G battery

Compounds

Oxidation state +3

The vast majority of compounds, including all Al-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 six-coordinate or tetracoordinate. Almost all compounds of aluminium(III) are colorless. Sony VAIO VGN-CS23G/W battery

Halides

All four trihalides are well known. Unlike the structures of the three heavier trihalides, aluminium fluoride (AlF3) features six-coordinate Al. The octahedral coordination environment for AlF3 is related to the compactness of fluoride ion, six of which can fit around the small Al3+ centre. AlF3 sublimes (with cracking) at 1,291 °C (2,356 °F) Sony VAIO VGN-CS23G/Q battery. With heavier halides, the coordination numbers are lower. The other trihalides are dimeric or polymeric with tetrahedral Al centers. These materials are prepared by treating aluminium metal with the halogen, although other methods exist. Acidification of the oxides or hydroxides affords hydrates. In aqueous solutionSony VAIO VGN-CS23G/P battery, the halides often form mixtures, generally containing six-coordinate Al centres, which are feature both halide and aquo ligands. When aluminium and fluoride are together in aqueous solution, they readily form complex ions such as [AlF(H2O)5]2+, AlF3(H2O)3, and [AlF6]3−. In the case of chloride, polyaluminium clusters are formed such as [Al13O4(OH)24(H2O)12]7+Sony VAIO VGN-CS21Z/Q battery.

Oxide and hydroxides

Aluminium forms one stable oxide, known by its mineral name corundum. Sapphire and ruby are impure corundum contaminated with trace amounts of other metals. The two oxide-hydroxides (AlO(OH) are boehmite and diaspore. There are three trihydroxides: bayerite, gibbsite, and nordstranditeSony VAIO VGN-CS21S/W battery, which differ in their crystalline structure (polymorphs). Most are produced from ores by a variety of wet processes using acid and base. Heating the hydroxides leads to formation of corundrum. These materials are of central importance to the production of aluminium and are themselves extremely usefulSony VAIO VGN-CS21S/V battery.

Carbide, nitride, and related materials

Aluminium carbide (Al4C3) is made by heating a mixture of the elements above 1,000 °C (1,832 °F). The pale yellow crystals consist of tetrahedral aluminium centres. It reacts with water or dilute acids to give methane. The acetylide, Al2(C2)3, is made by passing acetylene over heated aluminiumSony VAIO VGN-CS21S/T battery.

Aluminium nitride (AlN) is the only nitride known for aluminium. Unlike the oxides it features tetrahedral Al centres. It can be made from the elements at 800 °C (1,472 °F). It is air-stable material with a usefully high thermal conductivity. Aluminium phosphide (AlP) is made similarly, and hydrolyses to give phosphineSony VAIO VGN-CS21S/R battery:

AlP + 3 H2O → Al(OH)3 + PH3

Organoaluminium compounds and related hydrides

Main article: Organoaluminium compound

Structure of trimethylaluminium, a compound that features five-coordinate carbon.

A variety of compounds of empirical formula AlR3 and AlR1.5Cl1.5 exist.[31] These species usually feature tetrahedral Al centres, e.g. "trimethylaluminium" has the formula Al2(CH3)6 (see figure). With large organic groups, triorganoaluminium exist as three-coordinate monomers, such as triisobutylaluminiumSony VAIO VGN-CS21S/P battery. Such compounds are widely used in industrial chemistry, despite the fact that they are often highly pyrophoric. Few analogues exist between organoaluminium and organoboron compounds except for large organic groups.

The important aluminium hydride is lithium aluminium hydride (LiAlH4), which is used in as a reducing agent in organic chemistry. It can be produced from lithium hydride and aluminium trichlorideSony VAIO VGN-CS215J/R battery:

4 LiH + AlCl3 → LiAlH4 + 3 LiCl

Several useful derivatives of LiAlH4 are known, e.g. Sodium bis(2-methoxyethoxy)dihydridoaluminate. The simplest hydride, aluminium hydride or alane, remains a laboratory curiosity. It is a polymer with the formula (AlH3)n, in contrast to the corresponding boron hydride with the formula (BH3)2Sony VAIO VGN-CS19/W battery.

Oxidation states +1 and +2

Although the great majority of aluminium compounds feature Al3+ centres, compounds with lower oxidation states are known and sometime of significance as precursors to the Al3+ species.

Aluminium(I)

AlF, AlCl and AlBr exist in the gaseous phase when the tri-halide is heated with aluminium. The composition AlI is unstable at room temperature with respect to the triiodide: Sony VAIO VGN-CS19/R battery

3 AlI → AlI3 + 2 Al

A stable derivative of aluminium monoiodide is the cyclic adduct formed with triethylamine, Al4I4(NEt3)4. Also of theoretical interest but only of fleeting existence are Al2O and Al2S is made by heating the normal oxide, Al2O3, with silicon at 1,800 °C (3,272 °F) in a vacuum.[32] Such materials quickly disproportionates to the starting materialsSony VAIO VGN-CS19/Q battery.

Aluminium(II)

Very simple Al(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[33] and in stellar absorption spectra.[34] More thoroughly investigated are compounds of the formula R4Al2 where R is a large organic ligand. Sony VAIO VGN-CS19/P battery

Analysis

The presence of aluminium can be detected in qualitative analysis using aluminon.

Applications

General use

Aluminium is the most widely used non-ferrous metal.[36] Global production of aluminium in 2005 was 31.9 million tonnes. It exceeded that of any other metal except iron (837.5 million tonnes).[37] Forecast for 2012 is 42–45 million tonnes, driven by rising Chinese output. Sony VAIO VGN-CS17H/W battery

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.[39] The main alloying agents are copper, zinc, magnesium, manganese, and silicon (e.g., duralumin) and the levels of these other metals are in the range of a few percent by weight. Sony VAIO VGN-CS17H/Q battery

Household aluminium foil

Aluminium-bodied Austin "A40 Sports" (circa 1951)

Aluminium slabs being transported from a smelter

Some of the many uses for aluminium metal are in:

Transportation (automobiles, aircraft, trucks, railway cars, marine vessels, bicycles, etc.) as sheet, tube, castings, etc.

Packaging (cans, foil, etc.)

Construction (windows, doors, siding, building wire, etc.).[41]

A wide range of household items, from cooking utensils to baseball bats, watches.[42]

Street lighting poles, sailing ship masts, walking poles, etcSony VAIO VGN-CS16T/W battery.

Outer shells of consumer electronics, also cases for equipment e.g. photographic equipment.

Electrical transmission lines for power distribution

MKM steel and Alnico magnets

Super purity aluminium (SPA, 99.980% to 99.999% Al), used in electronics and CDs.

Heat sinks for electronic appliances such as transistors and CPUs.

Substrate material of metal-core copper clad laminates used in high brightness LED lightingSony VAIO VGN-CS16T/T battery.

Powdered aluminium is used in paint, and in pyrotechnics such as solid rocket fuels and thermite.

Aluminium can be reacted with hydrochloric acid or with sodium hydroxide to produce hydrogen gas.

A variety of countries, including France, Italy, Poland, Finland, Romania, Israel, and the former Yugoslavia, have issued coins struck in aluminium or aluminium-copper alloys. Sony VAIO VGN-CS16T/R battery

Some guitar models sports aluminium diamond plates on the surface of the instruments, usually either chrome or black. Kramer Guitars and Travis Bean are both known for having produced guitars with necks made of aluminium, which gives the instrument a very distinct soundSony VAIO VGN-CS16T/Q battery.

Aluminium is usually alloyed – it is used as pure metal only when corrosion resistance and/or workability is more important than strength or hardness. A thin layer of aluminium can be deposited onto a flat surface by physical vapour deposition or (very infrequently) chemical vapour deposition or other chemical means to form optical coatings and mirrorsSony VAIO VGN-CS16T/P battery.

Aluminium compounds

Because aluminium is abundant and most of its derivative exhibit low toxicity, the compounds of aluminium enjoy wide and sometimes large-scale applications.

Alumina

Main article: Aluminium oxide

Aluminium oxide (Al2O3) and the associated oxy-hydroxides and trihydroxides are produced or extracted from minerals on a large scale. The great majority of this material is converted to metallic aluminiumSony VAIO VGN-CS13T/W battery. About 10% of the production capacity is used for other applications. A major use is as an absorbent, for example alumina will remove water from hydrocarbons, to enable subsequent processes that are poisoned by moisture. Aluminium oxides are common catalysts for industrial processes, e.g. the Claus process for converting hydrogen sulfide to sulfur in refineries and for the alkylation of aminesSony VAIO VGN-CS13H/W battery. Many industrial catalysts are "supported", meaning generally that an expensive catalyst (e.g., platinum) is dispersed over a high surface area material such as alumina. Being a very hard material (Mohs hardness 9), alumina is widely used as an abrasive and the production of applications that exploit its inertness, e.g., in high pressure sodium lampsSony VAIO VGN-CS13H/R battery.

Sulfates

Several sulfates of aluminium find applications. Aluminium sulfate (Al2(SO4)3(H2O)18) is produced on the annual scale of several billions of kilograms. About half of the production is consumed in water treatment. The next major application is in the manufacture of paper. It is also used as a mordantSony VAIO VGN-CS13H/Q battery, in fire extinguisher, as a food additive, in fireproofing, and in leather tanning. Aluminium ammonium sulfate, which is also called ammonium alum, (NH4)Al(SO4)2·12H2O, is used as a mordant and in leather tanning.[5] Aluminium potassium sulfate ([Al(K)](SO4)2)(H2O)12 is used similarly. The consumption of both alums is decliningSony VAIO VGN-CS13H/P battery.

Chlorides

Aluminium chloride (AlCl3) is used in petroleum refining and in the production of synthetic rubber and polymers. Although it has a similar name, aluminium chlorohydrate has fewer and very different applications, e.g. as a hardening agent and an antiperspirant. It is an intermediate in the production of aluminium metalSony VAIO VGN-CS11Z/T battery.

Niche compounds

Given the scale of aluminium compounds, a small scale application could still involve thousands of tonnes. One of the many compounds used at this intermediate level include aluminium acetate, a salt used in solution as an astringent. Aluminium borate (Al2O3·B2O3) is used in the production of glass and ceramicsSony VAIO VGN-CS11Z/R battery. Aluminium fluorosilicate (Al2(SiF6)3) is used in the production of synthetic gemstones, glass and ceramic. Aluminium phosphate (AlPO4) is used in the manufacture: of glass and ceramic, pulp and paper products, cosmetics, paints and varnishes and in making dental cement. Aluminium hydroxide (Al(OH)3) is used as an antacid, as a mordant, in water purificationSony VAIO VGN-CS11S/W battery, in the manufacture of glass and ceramic 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 cocatalysts. For example, methylaluminoxane is a cocatalyst for Ziegler-Natta olefin polymerization to produce vinyl polymers such as polyetheneSony VAIO VGN-CS11S/Q battery.

Aluminium alloys in structural applications

Main article: Aluminium alloy

Aluminium foam

Aluminium alloys with a wide range of properties are used in engineering structures. Alloy systems are classified by a number system (ANSI) or by names indicating their main alloying constituents (DIN and ISO).

The strength and durability of aluminium alloys vary widely, not only as a result of the components of the specific alloy, but also as a result of heat treatments and manufacturing processesSony VAIO VGN-CS11S/P battery. A lack of knowledge of these aspects has from time to time led to improperly designed structures and gained aluminium a bad reputation.

One important structural limitation of aluminium alloys is their fatigue strength. Unlike steels, aluminium alloys have no well-defined fatigue limit, meaning that fatigue failure eventually occurs, under even very small cyclic loadings. This implies that engineers must assess these loads and design for a fixed life rather than an infinite life(Sony VAIO VGN-AW11M/H battery).

Another important property of aluminium alloys is their sensitivity to heat. Workshop procedures involving heating are complicated by the fact that aluminium, unlike steel, melts without first glowing red. Forming operations where a blow torch is used therefore require some expertise, since no visual signs reveal how close the material is to melting. Aluminium alloys, like all structural alloys(Sony VAIO VGN-AW11S/B battery), also are subject to internal stresses following heating operations such as welding and casting. The problem with aluminium alloys in this regard is their low melting point, which make them more susceptible to distortions from thermally induced stress relief. Controlled stress relief can be done during manufacturing by heat-treating the parts in an oven, followed by gradual cooling—in effect annealing the stresses(Sony VAIO VGN-AW11Z/B battery).

The low melting point of aluminium alloys has not precluded their use in rocketry; even for use in constructing combustion chambers where gases can reach 3500 K. The Agena upper stage engine used a regeneratively cooled aluminium design for some parts of the nozzle, including the thermally critical throat region.

Another alloy of some value is aluminium bronze (Cu-Al alloy) (Sony VAIO VGN-AW19/Q battery).

History

The statue of the Anteros (commonly mistaken for either The Angel of Christian Charity or Eros) in Piccadilly Circus, London, was made in 1893 and is one of the first statues to be cast in aluminium.

Ancient Greeks and Romans used aluminium salts as dyeing mordants and as astringents for dressing wounds; alum is still used as a styptic. In 1761, Guyton de Morveau suggested calling the base alum alumine(Sony VAIO VGN-AW19 battery). In 1808, Humphry Davy identified the existence of a metal base of alum, which he at first termed alumium and later aluminum (see etymology section, below).

The metal was first produced in 1825 in an impure form 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(Sony VAIO VGN-AW21M/H battery).[45] Friedrich Wöhler was aware of these experiments and cited them, but after redoing the experiments of Ørsted he concluded that this metal was pure potassium. He conducted a similar experiment in 1827 by mixing anhydrous aluminium chloride with potassium and yielded aluminium.[45] Wöhler is generally credited with isolating aluminium (Latin alumen, alum) (Sony VAIO VGN-AW21S/B battery), but also Ørsted can be listed as its discoverer.[46] Further, Pierre Berthier discovered aluminium in bauxite ore and successfully extracted it.[47] Frenchman Henri Etienne Sainte-Claire Deville improved Wöhler's method in 1846, and described his improvements in a book in 1859, chief among these being the substitution of sodium for the considerably more expensive potassium. (Sony VAIO VGN-AW21VY/Q battery) Deville likely also conceived the idea of the electrolysis of aluminium oxide dissolved in cryolite; Charles Martin Hall and Paul Héroult might have developed the more practical process after Deville.

Before the Hall-Héroult process was developed in the late 1880s, aluminium was exceedingly difficult to extract from its various ores. This made pure aluminium more valuable than gold. (Sony VAIO VGN-AW21XY/Q battery)Bars of aluminium were exhibited at the Exposition Universelle of 1855.[50] Napoleon III, Emperor of France, is reputed to have given a banquet where the most honoured guests were given aluminium utensils, while the others made do with gold.[51][52]

Aluminium was selected as the material to be used for the 100 ounce (2.8 kg) capstone of the Washington Monument in 1884, a time when one ounce (30 grams) cost the daily wage of a common worker on the project(Sony VAIO VGN-AW21Z/B battery);[53] The capstone, which was set in place on December 6, 1884, in an elaborate dedication ceremony, was the largest single piece of aluminium cast at the time, when aluminium was as expensive as silver.[53]

The Cowles companies supplied aluminium alloy in quantity in the United States and England using smelters like the furnace of Carl Wilhelm Siemens by 1886. (Sony VAIO VGN-AW31M/H battery)Charles Martin Hall of Ohio in the U.S. and Paul Héroult of France independently developed the Hall-Héroult electrolytic process that made extracting aluminium from minerals cheaper and is now the principal method used worldwide. Hall's process,[57] in 1888 with the financial backing of Alfred E. Hunt, started the Pittsburgh Reduction Company today known as Alcoa. (Sony VAIO VGN-AW31S/B battery) Héroult's process was in production by 1889 in Switzerland at Aluminium Industrie, now Alcan, and at British Aluminium, now Luxfer Group and Alcoa, by 1896 in Scotland.[58]

By 1895, the metal was being used as a building material as far away as Sydney, Australia in the dome of the Chief Secretary's Building.

Many navies have used an aluminium superstructure for their vessels(Sony VAIO VGN-AW31XY/Q battery); the 1975 fire aboard USS Belknap that gutted her aluminium superstructure, as well as observation of battle damage to British ships during the Falklands War, led to many navies switching to all steel superstructures. The Arleigh Burke class was the first such U.S. ship, being constructed entirely of steel(Sony VAIO VGN-AW31ZJ/B battery).

Aluminium wire was once widely used for domestic electrical wiring. Owing to corrosion-induced failures, a number of fires resulted. This discontinuation thus illustrates one failed application of the otherwise highly useful metal.

Etymology

Two variants of the metal's name are in current use, aluminium and aluminum (besides the obsolete alumium) (Sony VAIO VGN-AW41JF battery). The International Union of Pure and Applied Chemistry (IUPAC) adopted aluminium as the standard international name for the element in 1990 but, three years later, recognized aluminum as an acceptable variant. Hence their periodic table includes both.[59] IUPAC prefers the use of aluminium in its internal publications, although nearly as many IUPAC publications use the spelling aluminum. (Sony VAIO VGN-AW41MF/H battery)

Most countries use the spelling aluminium. In the United States, the spelling aluminum predominates.[14][61] The Canadian Oxford Dictionary prefers aluminum, whereas the Australian Macquarie Dictionary prefers aluminium. In 1926, the American Chemical Society officially decided to use aluminum in its publications; American dictionaries typically label the spelling aluminium as a British variant. (Sony VAIO VGN-AW41MF battery)

The name aluminium derives from its status as a base of alum. It is borrowed from Old French; its ultimate source, alumen, in turn is a Latin word that literally means "bitter salt".[62]

The earliest citation given in the Oxford English Dictionary for any word used as a name for this element is alumium, which British chemist and inventor Humphry Davy employed in 1808 for the metal he was trying to isolate electrolytically from the mineral alumina(Sony VAIO VGN-AW41XH/Q battery). The citation is from the journal Philosophical Transactions of the Royal Society of London: "Had I been so fortunate as to have obtained more certain evidences on this subject, and to have procured the metallic substances I was in search of, I should have proposed for them the names of silicium, alumium, zirconium, and glucium." (Sony VAIO VGN-AW41XH battery)

Davy settled on aluminum by the time he published his 1812 book Chemical Philosophy: "This substance appears to contain a peculiar metal, but as yet Aluminum has not been obtained in a perfectly free state, though alloys of it with other metalline substances have been procured sufficiently distinct to indicate the probable nature of alumina." (Sony VAIO VGN-AW41ZF/B battery) But the same year, an anonymous contributor to the Quarterly Review, a British political-literary journal, in a review of Davy's book, objected to aluminum and proposed the name aluminium, "for so we shall take the liberty of writing the word, in preference to aluminum, which has a less classical sound." (Sony VAIO VGN-AW41ZF battery)

The -ium suffix conformed to the precedent set in other newly discovered elements of the time: potassium, sodium, magnesium, calcium, and strontium (all of which Davy isolated himself). Nevertheless, -um spellings for elements were not unknown at the time, as for example platinum, known to Europeans since the 16th century, molybdenum, discovered in 1778, and tantalum, discovered in 1802. HP Pavilion dv6-1299lx battery The -um suffix is consistent with the universal spelling alumina for the oxide, as lanthana is the oxide of lanthanum, and magnesia, ceria, and thoria are the oxides of magnesium, cerium, and thorium respectively.

The spelling used throughout the 19th century by most U.S. chemists was aluminium, but common usage is less clearHP Pavilion dv6-1299ez battery.[67] The aluminum spelling is used in the Webster's Dictionary of 1828. In his advertising handbill for his new electrolytic method of producing the metal 1892, Charles Martin Hall used the -um spelling, despite his constant use of the -ium spelling in all the patents[57] he filed between 1886 and 1903.[68] It has consequently been suggested that the spelling reflects an easier to pronounce word with one fewer syllableHP Pavilion dv6-1299es battery, or that the spelling on the flier was a mistake. Hall's domination of production of the metal ensured that the spelling aluminum became the standard in North America; the Webster Unabridged Dictionary of 1913, though, continued to use the -ium version.

Health concerns

NFPA 704

000

Fire diamond for aluminium shot

Despite its natural abundance, aluminium has no known function in biology. It is remarkably nontoxicHP Pavilion dv6-1299er battery, aluminium sulfate having an LD50 of 6207 mg/kg (oral, mouse), which corresponds to 500 grams for a 80 kg person.[5] Despite the extremely low acute toxicity, the health effects of aluminium are of interest in view of the widespread occurrence of the element in the environment and in commerceHP Pavilion dv6-1299eo battery.

Some toxicity can be traced to deposition in bone and the central nervous system, which is particularly increased in patients with reduced renal function. Because aluminium competes with calcium for absorption, increased amounts of dietary aluminium may contribute to the reduced skeletal mineralization (osteopenia) observed in preterm infants and infants with growth retardationHP Pavilion dv6-1299ef battery. In very high doses, aluminium can cause neurotoxicity, and is associated with altered function of the blood-brain barrier.[69] A small percentage of people are allergic to aluminium and experience contact dermatitis, digestive disorders, vomiting or other symptoms upon contact or ingestion of products containing aluminiumHP Pavilion dv6-1299ea battery, such as deodorants or antacids. In those without allergies, aluminium is not as toxic as heavy metals, but there is evidence of some toxicity if it is consumed in excessive amounts.[70] Although the use of aluminium cookware has not been shown to lead to aluminium toxicity in general, excessive consumption of antacids containing aluminium compounds and excessive use of aluminium-containing antiperspirants provide more significant exposure levelsHP Pavilion dv6-1295el battery. Studies have shown that consumption of acidic foods or liquids with aluminium significantly increases aluminium absorption,[71] and maltol has been shown to increase the accumulation of aluminium in nervous and osseus tissue.[72] Furthermore, aluminium increases estrogen-related gene expression in human breast cancer cells cultured in the laboratory. HP Pavilion dv6-1291es battery The estrogen-like effects of these salts have led to their classification as a metalloestrogen.

The effects of aluminium in antiperspirants has been examined over the course of decades with little evidence of skin irritation.[5] Nonetheless, its occurrence in antiperspirants, dyes (such as aluminium lake), and food additives is controversial in some quartersHP Pavilion dv6-1290ev battery. Although there is little evidence that normal exposure to aluminium presents a risk to healthy adults,[74] some studies point to risks associated with increased exposure to the metal.[75] Aluminium in food may be absorbed more than aluminium from water.[76] Some researchers have expressed concerns that the aluminium in antiperspirants may increase the risk of breast cancer, HP Pavilion dv6-1290es battery and aluminium has controversially been implicated as a factor in Alzheimer's disease.[78] The Camelford water pollution incident involved a number of people consuming aluminium sulfate. Investigations of the long-term health effects are still ongoing, but elevated brain aluminium concentrations have been found in post-mortem examinations of victims, and further research to determine if there is a link with cerebral amyloid angiopathy has been commissionedHP Pavilion dv6-1290en battery.[79]

According to The Alzheimer's Society, the overwhelming medical and scientific opinion is that studies have not convincingly demonstrated a causal relationship between aluminium and Alzheimer's disease.[80] Nevertheless, some studies, such as those on the PAQUID cohort,[81] cite aluminium exposure as a risk factor for Alzheimer's diseaseHP Pavilion dv6-1290ec battery. Some brain plaques have been found to contain increased levels of the metal.[82] Research in this area has been inconclusive; aluminium accumulation may be a consequence of the disease rather than a causal agent. In any event, if there is any toxicity of aluminium, it must be via a very specific mechanism, since total human exposure to the element in the form of naturally occurring clay in soil and dust is enormously large over a lifetime. HP Pavilion dv6-1288la battery Scientific consensus does not yet exist about whether aluminium exposure could directly increase the risk of Alzheimer's disease.[80]

Effect on plants

Aluminium is primary among the factors that reduce plant growth on acid soils. Although it is generally harmless to plant growth in pH-neutral soils, the concentration in acid soils of toxic Al3+ cations increases and disturbs root growth and function.HP Pavilion dv6-1210ee battery

Most acid soils are saturated with aluminium rather than hydrogen ions. The acidity of the soil is therefore a result of hydrolysis of aluminium compounds.[89] This concept of "corrected lime potential"[90] to define the degree of base saturation in soils became the basis for procedures now used in soil testing laboratories to determine the "lime requirement"[91] of soilsHP Pavilion dv6-1210eg battery.[92]

Wheat's adaptation to allow aluminium tolerance is such that the aluminium induces a release of organic compounds that bind to the harmful aluminium cations. Sorghum is believed to have the same tolerance mechanism. The first gene for aluminium tolerance has been identified in wheat. It was shown that sorghum's aluminium tolerance is controlled by a single gene, as for wheat.[93] This is not the case in all plantsHP Pavilion dv6-1210ek battery.

Lead ( /ˈlɛd/) is a main-group element in the carbon group with the symbol Pb (from Latin: plumbum) and atomic number 82. Lead is a soft, malleable poor metal. It is also counted as one of the heavy metals. Metallic lead has a bluish-white color after being freshly cut, but it soon tarnishes to a dull grayish color when exposed to air. Lead has a shiny chrome-silver luster when it is melted into a liquidHP Pavilion dv6-1210er battery.

Lead is used in building construction, lead-acid batteries, bullets and shots, weights, as part of solders, pewters, fusible alloys and as a radiation shield. Lead has the highest atomic number of all of the stable elements, although the next higher element, bismuth, has a half-life that is so long (much longer than the age of the universe) that it can be considered stableHP Pavilion dv6-1210es battery. Its four stable isotopes have 82 protons, a magic number in the nuclear shell model of atomic nuclei.

Lead, at certain exposure levels, is a poisonous substance to animals as well as for human beings. It damages the nervous system and causes brain disorders. Excessive lead also causes blood disorders in mammals. Like the element mercury, another heavy metal, lead is a neurotoxin that accumulates both in soft tissues and the bonesHP Pavilion dv6-1210et battery. Lead poisoning has been documented from ancient Rome, ancient Greece, and ancient China.

Characteristics

A sample of recently solidified lead (from a molten state)

Lead is a bright and silvery (with a very slight shade of blue[1]) metal in a dry atmosphere; upon contact with air, it begins to tarnish. It has a few characteristic properties: high density, softness, ductility and malleability, poor electrical conductivity (compared to other metals), high resistance to corrosion, and ability to react with organic chemicals. HP Pavilion dv6-1210ew battery

Various traces of other metals change its properties significantly: addition of small amounts of antimony or copper increases hardness and improves the corrosion reflection from sulfuric acid for lead.[1] A few other metals also improve only hardness and fight the metal fatigue, such as cadmium, tin, or telluriumHP Pavilion dv6-1210ez battery; metals like sodium or calcium also have this ability, but they weaken the chemical stability.[1] Finally, zinc and bismuth simply impair the corrosion resistance (0.1% bismuth content prevent lead from the industrial usage).[1] In return, lead impurities mostly worsen the quality of industrial materials, although there are exceptions: for example, small amounts of lead improve the ductility of steel.HP Pavilion dv6-1210sa battery [1]

Lead has only one common allotrope, which is face-centered cubic, with the lead–lead distance being 349 pm.[2] At 327.5 °C (621.5 °F),[3] lead melts; the melting point is above that of tin (232 °C, 449.5 °F),[3] but significantly below that of germanium (938 °C, 1721 °F).[4] The boiling point of lead is 1749 °C (3180 °F),[5] which is below than those of both tin (2602 °C, 4716 °F)[3] and germanium (2833 °C, 5131 °F) HP Pavilion dv6-1210sb battery.[4] Densities get simply bigger down the group: the Ge and Sn values (5.23[6] and 7.29 g·cm−3,[7] respectively) are significantly below that of lead: 11.32 g·cm−3.[6]

A lead atom has 82 electrons, having an electronic configuration of [Xe]4f145d106s26p2. In its compounds, lead (unlike the other group 14 elements) most commonly loses its two and not four outermost electrons, becoming lead(II) ions, Pb2+. Such unusual behavior is rationalized by considering the inert pair effectHP Pavilion dv6-1210sf battery, which occurs because of the stabilization of 6s-orbital due to relativistic effects, which are stronger closer to the bottom of the periodic table.[8] Tin shows a weaker such effect: tin(II) is still a reducer.[8]

The figures for electrode potential show that lead is only slightly easier to oxidize than hydrogen. Lead thus can dissolve in acids, but this is often impossible due to specific problems (such as insoluble salts formation) HP Pavilion dv6-1210sl battery.[9] Powdered lead burns with a bluish-white flame. As with many metals, finely divided powdered lead exhibits pyrophoricity.[10] Toxic fumes are released when lead is burned.

Isotopes

Main article: Isotopes of lead

Lead occurs naturally on Earth exclusively in the form of four isotopes: lead-204, -206, -207, and -208.[11] All four can be radioactive as the hypothetical alpha decay of any would release energy, but the lower half-life limit has been put only for lead-204: over 1.4×1017 yearsHP Pavilion dv6-1210sr battery.[12] This effect is, however, so weak that natural lead makes no radiation hazard. Three of them are also found in three of the four major decay chains: lead-206, -207 and -208 are final decay products of uranium-238, uranium-235, and thorium-232, respectively. Since the amounts of them in nature depend also on other elements' presenceHP Pavilion dv6-1210sv battery, the isotopic composition of natural lead varies by sample: in particular, the relative amount of lead-206 varies between 20.84% and 27.78%.[11]

Aside from the stable ones, thirty-four radioisotopes have been synthesized: they have the mass numbers of 178–215.[12] Lead-205 is the most stable radioisotope of lead, with a half-life of over 107 years. 47 nuclear isomers (long-lived excited nuclear states), corresponding to 24 lead isotopes, have been characterized. The most long-lived is lead-204m2 (half-life of about 1.1 hours). HP Pavilion dv6-1210tx battery

Chemical reactivity

Lead is chemically a post-transition metal and belongs to the group 14 of the periodic table. It shows two main oxidation states, which are +2 and +4. The former is more stable, while the +4 oxidation state, favored for the rest of the group, is an oxidizer; lead(IV) ions exist only in highly acidic solutionsHP Pavilion dv6-1211ax battery.[8]

Cold thoroughly crushed lead may ignite in the air, as it is attacked by oxygen in it; compact lead only form a protective oxide layer. Melted lead is oxidized in the air to become lead monoxide. At 430 °C (810 °F), it is further oxidized to become trilead tetroxide, which decomposes at 550 °C (1020 °F) to turn back into PbO. All chalcogens oxidize lead upon heating; during the reaction with sulfur, the metal may be heated to get red. HP Pavilion dv6-1211er battery

Fluorine does not oxidize cold lead. Hot lead can be oxidized, but the formation on a protective halide layer lowers the intensity of the reaction above 100 °C (210 °F). The reaction with chlorine is similar: thanks to the chloride layer, lead persistence against chlorine surpasses those of copper or steel up to 300 °C (570 °F). HP Pavilion dv6-1211sa battery

Water in presence of oxygen attacks lead to start an accelerating reaction. Presence of carbonates or sulfates lead to formation of insoluble lead salts, which prevent the metal from corrosion. So does carbon dioxide, as the insoluble lead carbonate is formed; however, excess of the gas leads to the formation of the soluble bicarbonateHP Pavilion dv6-1211sg battery; this dangers the usage of lead pipes.[9] Lead dissolves in organic acids (in presence of oxygen) and concentrated (≥80%) sulfuric acid thanks to complexation; however, it is only weakly affected by hydrochloric acid and is stable against hydrofluoric acid, as the corresponding halides are weakly soluble. Lead also dissolves in quite concentrated alkalis (≥10%) thanks to the amphoteric character and solubility of plumbitesHP Pavilion dv6-1211tx battery.[9]

Compounds

Main article: Compounds of lead

Oxides and sulfide

There are three oxides known: PbO, Pb3O4 (sometimes called "minium"), and PbO2. The former has two allotropes: α-PbO and β-PbO, both with layer structure and tetracoordinated lead. The alpha allotrope is red-colored and has the Pb–O distance of 230 pm; the beta allotrope is yellow-colored and has the Pb–O distance of 221 and 249 pm (due to asymmetry) HP Pavilion dv6-1212sl battery.[14] Thanks to the similarity, both allotropes can exist under standard conditions (beta with small (10-5 relative) impurities, such as Si, Ge, Mo, etc.). PbO reacts with acids to form salts, and with alkalies to give plumbites, [Pb(OH)3]- or [Pb(OH)4]2-.[15]

The dioxide may be prepared by, for example, halogenization of lead(II) salts. Regardless the allotrope, it has a black-brown colorHP Pavilion dv6-1212tx battery. The alpha allotrope is rhombohedral, and the beta allotrope is tetragonal.[15] Both allotropes are black-brown in color and always contain some water, which cannot be removed, as heating also causes decomposition (to PbO and Pb3O4). The dioxide is a powerful oxidizer: it can oxidize hydrochloric and sulfuric acids. It does not reacts with alkaline solution, but reacts with solid alkalies to give hydroxyplumbatesHP Pavilion dv6-1213ax battery, or with basic oxides to give plumbates.[15]

Reaction of lead with sulfur or hydrogen sulfide yields lead sulfide. The solid has the NaCl-like striucture (simple cubic), which it keeps up to the melting point, 1114 °C (2037 °F). If the heating occurs in presence of air, the compounds decomposes to give the monoxide and the sulfateHP Pavilion dv6-1213tx battery.[16] The compounds is almost insoluble in water, weak acids, and (NH4)2S/(NH4)2S2 solution is the key for separation of lead from analythical groups I to III elements, tin, arsenic, and antimony. The compounds, however, dissolves in nitric and hydrochloric acids, to give elemental sulfur and hydrogen sulfide, respectively.[16] Heating a mixture of the monoxide and the sulfide heated together forms the metal. HP Pavilion dv6-1214ax battery

2 PbO + PbS → 3 Pb + SO2↑

Halides and other salts

Heating lead carbonate with hydrogen fluoride yields the hydrofluoride, which decomposes to the difluoride when melts. This white crystalline powder is more soluble than the diiodide, but less than the dibromide and the dichloride. No coordinated lead fluorides exist (except the unstable PbF+ cation).[18] The tetrafluoride, a yellow crystalline powder, is unstableHP Pavilion dv6-1214sl battery.

Other dihalides are received upon heating lead(II) salts with the halides of other metals; lead dihalides precipitate to give white orthorhombic crystals (diiodide form yellow hexagonal crystals). They can also be obtained by direct elements reaction at temperature exceeding melting points of dihalides. Their solubility increases with temperatureHP Pavilion dv6-1214tx battery; adding more halides first decreases the solubility, but then increases due to complexation, with the maximum coordination number being 6. The complexation depends on halide ion numbers, atomic number of the alkali metal, the halide of which is added, temperature and solution ionic strength.[19] The tetrachloride is obtained upon dissolving the dioxide in hydrochloric acid; to prevent the exothermic decompositionHP Pavilion dv6-1215ax battery, it is kept under concentrated sulfuric acid. The tetrabromide may not, and the tetraiodide definitely does not exist.[20] The diastatide has also been prepared.[21]

The metal is not attacked by sulfuric or hydrochloric acids. It dissolves in nitric acid with the evolution of nitric oxide gas to form dissolved Pb(NO3)2.[18] It is a well-soluble solid in water; it is thus a key to receive the precipitates of halide, sulfate, chromate, carbonate, and basic carbonate Pb3(OH)2(CO3)2 salts of lead. HP Pavilion dv6-1215ee battery

Organolead

Main article: Organolead compound

The best-known compounds are the two simplest plumbane deratives: tetramethyllead (TML) and tetraethyllead (TEL); however, the homologs of these, as well as hexaethyldilead (HEDL), are of lesser stability. The tetralkyl deratives contain lead(IV); the Pb–C bonds are covalent. They thus resemble typical organic compounds. HP Pavilion dv6-1215ei battery

Lead readily forms an equimolar alloy with sodium metal that reacts with alkyl halides to form organometallic compounds of lead such as tetraethyllead.[24] The Pb–C bongs energies in TML and TEL are only 167 and 145 kJ/mol; the compounds thus decompose upon heating, with first signs of TEL composition seen at 100 °C (210 °F) HP Pavilion dv6-1215er battery. The pyrolisis yields of elemental lead and alkyl radicals; their interreaction causes the synthesis of HEDL.[23] They also decompose upon sunlight or UV-light.[25] In presence of chlorine, the alkyls begin to be replaced with chlorides; the R2PbCl2 in the presence of HCl (a by-product of the previous reaction) leads to the complete mineralization to give PbCl2. Reaction with bromine follows the same principle. HP Pavilion dv6-1215ew battery

History

World lead production peaking in the Roman period and the rising Industrial Revolution[26]

Lead ingots from Roman Britain on display at the Wells and Mendip Museum

Lead mining in the upper Mississippi River region of the U.S., 1865.

Lead has been commonly used for thousands of years because it is widespread, easy to extract and easy to work with. It is highly malleable and ductile as well as easy to smelt. Metallic lead beads dating back to 6400 BCE have been found in Çatalhöyük in modern-day Turkey.[27] In the early Bronze Age, lead was used with antimony and arsenicHP Pavilion dv6-1215ez battery.

The largest preindustrial producer of lead was the Roman economy, with an estimated output per annum of 80,000 t, which was typically won as a by-product of extensive silver smelting.[26][28][29] Roman mining activities occurred in Central Europe, Roman Britain, the Balkans, Greece, Asia Minor; Hispania alone accounted for 40% of world production. HP Pavilion dv6-1215sa battery

Roman lead pipes often bore the insignia of Roman emperors (see Roman lead pipe inscriptions). Lead plumbing in the Latin West may have been continued beyond the age of Theoderic the Great into the medieval period.[30] Many Roman "pigs" (ingots) of lead figure in Derbyshire lead mining history and in the history of the industry in other English centersHP Pavilion dv6-1215sd battery. The Romans also used lead in molten form to secure iron pins that held together large limestone blocks in certain monumental buildings. In alchemy, lead was thought to be the oldest metal and was associated with the planet Saturn. Alchemists accordingly used Saturn's symbol (the scythe, ♄) to refer to leadHP Pavilion dv6-1215sf battery.

Up to the 17th century, tin was often not differed from lead: lead was called plumbum nigrum (literally, "black plumbum"), while tin was called plumbum candidum (literally, "bright plumbum").[31] Their inherence through history can be seen in other languages: the word "olovo" stands for lead in Czech, but in Russian it ("олово") stands for tinHP Pavilion dv6-1215sg battery. Lead's symbol Pb is an abbreviation of its Latin name plumbum for soft metals; the English words "plumbing", "plumber", "plumb", and "plumb-bob" also derive from this Latin root.

Occurrence

Lead and zinc bearing carbonate and clastic deposits. Source: USGS

Metallic lead does occur in nature, but it is rare. Lead is usually found in ore with zinc, silver and (most abundantly) copper, and is extracted together with these metals. The main lead mineral is galena (PbS), which contains 86.6 % lead by weight. Other common varieties are cerussite (PbCO3) and anglesite (PbSO4) HP Pavilion dv6-1215sl battery.

Ore processing

Galena, lead ore

Most ores contain less than 10% lead, and ores containing as little as 3% lead can be economically exploited. Ores are crushed and concentrated by froth flotation typically to 70% or more. Sulfide ores are roasted, producing primarily lead oxide and a mixture of sulfates and silicates of lead and other metals contained in the ore. HP Pavilion dv6-1215ss battery

Lead oxide from the roasting process is reduced in a coke-fired blast furnace.[33] This converts most of the lead to its metallic form. Three additional layers separate in the process and float to the top of the metallic lead. These are slag (silicates containing 1.5% lead), matte (sulfides containing 15% lead), and speiss (arsenides of iron and copper) HP Pavilion dv6-1215tx battery. These wastes contain concentrations of copper, zinc, cadmium, and bismuth that can be recovered economically, as can their content of unreduced lead.[32]

Metallic lead that results from the roasting and blast furnace processes still contains significant contaminants of arsenic, antimony, bismuth, zinc, copper, silver, and gold. The melt is treated in a reverberatory furnace with air, steam, and sulfur, which oxidizes the contaminants except silver, gold, and bismuthHP Pavilion dv6-1216ax battery. The oxidized contaminants are removed by drossing, where they float to the top and are skimmed off.[32][34]

Most lead ores contain significant concentrations of silver, resulting in the smelted metal also containing silver as a contaminant. Metallic silver as well as gold is removed and recovered economically by means of the Parkes process. HP Pavilion dv6-1216er battery

Desilvered lead is freed of bismuth according to the Betterton-Kroll process by treating it with metallic calcium and magnesium, which forms a bismuth dross that can be skimmed off.[32][34]

Very pure lead can be obtained by processing smelted lead electrolytically by means of the Betts process. The process uses anodes of impure lead and cathodes of pure lead in an electrolyte of silica fluoride. HP Pavilion dv6-1216sa battery

Production and recycling

Production and consumption of lead is increasing worldwide. Total annual production is about 8 million tonnes; about half is produced from recycled scrap. The top lead producing countries, as of 2008, are Australia, China, USA, Peru, Canada, Mexico, Sweden, Morocco, South Africa and North Korea.[35] Australia, China and the United States account for more than half of primary production. HP Pavilion dv6-1216sl battery

In 2010, 9.6 million tonnes of lead were produced, of which 4.1 million tonnes came from mining.[37]

At current use rates, the supply of lead is estimated to run out in 42 years.[38] Environmental analyst Lester Brown has suggested lead could run out within 18 years based on an extrapolation of 2% growth per year.[39] This may need to be reviewed to take account of renewed interest in recycling, and rapid progress in fuel cell technologyHP Pavilion dv6-1216ss battery. According to the International Resource Panel's Metal Stocks in Society report, the global per capita stock of lead in use in society is 8 kg. Much of this is in more-developed countries (20–150 kg per capita) rather than less-developed countries (1–4 kg per capita).

Applications

Elemental form

Lead bricks are commonly used as radiation shielding.

Because of its high density and resistance from corrosion, lead is used for the ballast keel of sailboatsHP Pavilion dv6-1216tx battery. Its high density allows it to counterbalance the heeling effect of wind on the sails while at the same time occupying a small volume and thus offering the least underwater resistance. For the same reason it is used in scuba diving weight belts to counteract the diver's natural buoyancy and that of his equipment. It does not have the weight-to-volume ratio of many heavy metals, but its low cost increases its use in these and other applicationsHP Pavilion dv6-1217ax battery.

Roman lead water pipes with taps

Lead pipe in Roman baths

Multicolor lead-glazing in a sancai ceramic cup, Tang dynasty, China, 8th century CE.

Lead is used in applications where its low melting point, ductility and high density is an advantage. The low melting point makes casting of lead easy, and therefore small arms ammunition and shotgun pellets can be cast with minimal technical equipmentHP Pavilion dv6-1217er battery. It is also inexpensive and denser than other common metals.[40] The hot metal typesetting uses a lead based alloy to produce the types for printing directly before printing.

Its corrosion resistance makes it suitable for outdoor applications when in contact with water.

More than half of the worldwide lead production (at least 1.15 million metric tons) is used for automobiles, mostly as electrodes in the lead–acid battery, used extensively as a car battery. HP Pavilion dv6-1217ss battery

Cathode (reduction)

PbO2 + 4 H+ + SO42– + 2e– → PbSO4 + 2 H2O

Anode (oxidation)

Pb + SO42– → PbSO4 + 2e–[42][43]

Lead is used as electrodes in the process of electrolysis. Lead is used in solder for electronics, although this usage is being phased out by some countries to reduce the amount of environmentally hazardous waste. Lead is used in high voltage power cables as sheathing material to prevent water diffusion into insulationHP Pavilion dv6-1217tx battery.

Lead is one of three metals used in the Oddy test for museum materials, helping detect organic acids, aldehydes, and acidic gases.

Lead is used as shielding from radiation (e.g., in X-ray rooms).[44] Molten lead is used as a coolant (e.g., for lead cooled fast reactors).[45]

Lead is added to brass to reduce machine tool wear. Lead, in the form of strips, or tape, is used for the customization of tennis rackets. Tennis rackets of the past sometimes had lead added to them by the manufacturer to increase weight. HP Pavilion dv6-1218ca battery

Lead is used to form glazing bars for stained glass or other multi-lit windows. The practice has become less common, not for danger but for stylistic reasons. Lead, or sheet-lead, is used as a sound deadening layer in some areas in wall, floor and ceiling design in sound studios where levels of airborne and mechanically produced sound are targeted for reduction or virtual elimination. HP Pavilion dv6-1218ss battery

Lead is the traditional base metal of organ pipes, mixed with varying amounts of tin to control the tone of the pipe.[49][50]

Lead has many uses in the construction industry (e.g., lead sheets are used as architectural metals in roofing material, cladding, flashing, gutters and gutter joints, and on roof parapets). Detailed lead moldings are used as decorative motifs used to fix lead sheet. Lead is still widely used in statues and sculpturesHP Pavilion dv6-1218tx battery. Lead is often used to balance the wheels of a car; this use is being phased out in favor of other materials for environmental reasons.

Due to its half-life of 22.2 years, the radioactive isotope 210Pb is used for dating material from marine sediment cores byradiometric methods.[citation needed]

Compounds

Lead compounds are used as a coloring element in ceramic glazes, notably in the colors red and yellow.[51] Lead is frequently used in polyvinyl chloride (PVC) plastic, which coats electrical cords. HP Pavilion dv6-1219ez battery

Lead is used in some candles to treat the wick to ensure a longer, more even burn. Because of the dangers, European and North American manufacturers use more expensive alternatives such as zinc.[54][55] Lead glass is composed of 12–28% lead oxide. It changes the optical characteristics of the glass and reduces the transmission of radiation. HP Pavilion dv6-1219tx battery

Some artists using oil-based paints continue to use lead carbonate white, citing its properties in comparison with the alternatives. Tetra-ethyl lead is used as an anti-knock additive for aviation fuel in piston-driven aircraft. Lead-based semiconductors, such as lead telluride, lead selenide and lead antimonide are finding applications in photovoltaic (solar energy) cells and infrared detectors. HP Pavilion dv6-1220ec battery

Former applications

Lead pigments were used in lead paint for white as well as yellow, orange, and red. Most uses have been discontinued due of the dangers of lead poisoning. Beginning April 22, 2010, US federal law requires that contractors performing renovation, repair, and painting projects that disturb more than six square feet of paint in homesHP Pavilion dv6-1220eg battery, child care facilities, and schools built before 1978 must be certified and trained to follow specific work practices to prevent lead contamination. Lead chromate is still in industrial use. Lead carbonate (white) is the traditional pigment for the priming medium for oil painting, but it has been largely displaced by the zinc and titanium oxide pigmentsHP Pavilion dv6-1220ei battery. It was also quickly replaced in water-based painting mediums. Lead carbonate white was used by the Japanese geisha and in the West for face-whitening make-up, which was detrimental to health.[58][59][60]

Lead is the hot metal that was used in hot metal typesetting. It was used for plumbing as well as a preservative for food and drink in Ancient Rome. Until the early 1970s, lead was used for joining cast iron water pipes and used as a material for small diameter water pipes. HP Pavilion dv6-1220ek battery

Tetraethyllead was used in leaded fuels to reduce engine knocking, but this practice has been phased out across many countries of the world in efforts to reduce toxic pollution that affected humans and the environment.

Lead was used to make bullets for slings. Lead was used for shotgun pellets in the US until about 1992 when it was outlawed (for waterfowl hunting only) and replaced by non-toxic shot, primarily steel pelletsHP Pavilion dv6-1220er battery. In the Netherlands, the use of lead shot for hunting and sport shooting was banned in 1993, which caused a large drop in lead emission, from 230 ton in 1990 to 47.5 ton in 1995, two years after the ban.[66]

Lead was a component of the paint used on children's toys – now restricted in the United States and across Europe (ROHS Directive). Lead was used in car body filler, which was used in many custom cars in the 1940s–60sHP Pavilion dv6-1220ev battery. Hence the term Leadsled. Lead is a superconductor at 7.2 K and IBM tried to make a Josephson effect computer out of lead-alloy.[67]

Lead was also used in pesticides before the 1950s, when fruit orchards were treated (ATSDR). A lead cylinder attached to a long line was used by sailors for the vital navigational task of determining water depth by heaving the lead at regular internalsHP Pavilion dv6-1220ew battery. A soft tallow insert at its base allowed the nature of the sea bed to be determined, further aiding position finding. Contrary to popular belief, pencil leads in wooden pencils have never been made from lead. The term comes from the Roman stylus, called the penicillus, which was made of lead without a wooden holderHP Pavilion dv6-1220ez battery.[68] When the pencil originated as a wrapped graphite writing tool, the particular type of graphite being used was named plumbago (lit. act for lead, or lead mockup).

Health effects

Main article: Lead poisoning

Lead is highly poisonous metal (regardless if inhaled or swallowed), affecting almost every organ and system in the body. The main target for lead toxicity is the nervous system, both in adults and childrenHP Pavilion dv6-1220sa battery. Long-term exposure of adults can result in decreased performance in some tests that measure functions of the nervous system. Long-term exposure to lead or its salts (especially soluble salts or the strong oxidant PbO2) can cause nephropathy, and colic-like abdominal pains. It may also cause weakness in fingers, wrists, or ankles. Lead exposure also causes small increases in blood pressureHP Pavilion dv6-1220sb battery, particularly in middle-aged and older people and can cause anemia. Exposure to high lead levels can severely damage the brain and kidneys in adults or children and ultimately cause death. In pregnant women, high levels of exposure to lead may cause miscarriage. Chronic, high-level exposure have shown to reduce fertility in malesHP Pavilion dv6-1220sd battery.[69] Lead also damages nervous connections (especially in young children) and cause blood and brain disorders. Lead poisoning typically results from ingestion of food or water contaminated with lead; but may also occur after accidental ingestion of contaminated soil, dust, or lead-based paint.[70] It is rapidly absorbed into the bloodstream and is believed to have adverse effects on the central nervous systemHP Pavilion dv6-1220sh battery, the cardiovascular system, kidneys, and the immune system.[71] The component limit of lead (1.0 μg/g) is a test benchmark for pharmaceuticals, representing the maximum daily intake an individual should have. However, even at this low level, a prolonged intake can be hazardous to human beings.[72][73] The treatment for lead poisoning consists of dimercaprol and succimer. HP Pavilion dv6-1220so battery

NFPA 704

130

Fire diamond for lead granules

The concern about lead's role in cognitive deficits in children has brought about widespread reduction in its use (lead exposure has been linked to learning disabilities).[75] Most cases of adult elevated blood lead levels are workplace-related.[76] High blood levels are associated with delayed puberty in girls. HP Pavilion dv6-1220sp battery Lead has been shown many times to permanently reduce the cognitive capacity of children at extremely low levels of exposure.[78]

During the 20th century, the use of lead in paint pigments was sharply reduced because of the danger of lead poisoning, especially to children.[79][80] By the mid-1980s, a significant shift in lead end-use patterns had taken placeHP Pavilion dv6-1220ss battery. Much of this shift was a result of the U.S. lead consumers' compliance with environmental regulations that significantly reduced or eliminated the use of lead in non-battery products, including gasoline, paints, solders, and water systems. Lead use is being further curtailed by the European Union's RoHS directive. Lead may still be found in harmful quantities in stonewareHP Pavilion dv6-1220st battery, vinyl (such as that used for tubing and the insulation of electrical cords), and Chinese brass. Older houses may still contain substantial amounts of lead paint. White lead paint has been withdrawn from sale in industrialized countries, but the yellow lead chromate is still in use. Old paint should not be stripped by sanding, as this produces inhalable dustHP Pavilion dv6-1220tx battery.

Lead salts used in pottery glazes have on occasion caused poisoning, when acidic drinks, such as fruit juices, have leached lead ions out of the glaze.[81] It has been suggested that what was known as "Devon colic" arose from the use of lead-lined presses to extract apple juice in the manufacture of ciderHP Pavilion dv6-1221ax battery. Lead is considered to be particularly harmful for women's ability to reproduce. Lead(II) acetate (also known as sugar of lead) was used by the Roman Empire as a sweetener for wine, and some consider this to be the cause of the dementia that affected many of the Roman Emperors and even be a partial reason for the Roman Empire's fall (see Decline of the Roman Empire#Lead poisoning). HP Pavilion dv6-1221eo battery

Biochemistry of poisoning

In the human body, lead inhibits porphobilinogen synthase and ferrochelatase, preventing both porphobilinogen formation and the incorporation of iron into protoporphyrin IX, the final step in heme synthesis. This causes ineffective heme synthesis and subsequent microcytic anemia.[83] At lower levels, it acts as a calcium analog, interfering with ion channels during nerve conduction. This is one of the mechanisms by which it interferes with cognitionHP Pavilion dv6-1221sl battery. Acute lead poisoning is treated using disodium calcium edetate: the calcium chelate of the disodium salt of ethylene-diamine-tetracetic acid (EDTA). This chelating agent has a greater affinity for lead than for calcium and so the lead chelate is formed by exchange. This is then excreted in the urine leaving behind harmless calcium. HP Pavilion dv6-1221tx battery

Exposure to lead and lead chemicals can occur through inhalation, ingestion and dermal contact. Most exposure occurs through ingestion or inhalation; in the U.S. the skin exposure is unlikely as leaded gasoline additives are no longer used. Lead exposure is a global issue as lead mining and lead smelting are common in many countries. Most countries have stopped using lead-containing gasoline by 2007. HP Pavilion dv6-1222eo battery

Lead exposure mostly occurs through ingestion. Lead paint is the major source of lead exposure for children. As lead paint deteriorates, it peels, is pulverized into dust and then enters the body through hand-to-mouth contact or through contaminated food, water or alcohol. Ingesting certain home remedy medicines may also expose people to lead or lead compounds. HP Pavilion dv6-1222et battery Lead can be ingested through fruits and vegetables contaminated by high levels of lead in the soils they were grown in. Soil is contaminated through particulate accumulation from lead in pipes, lead paint and residual emissions from leaded gasoline that was used before the Environment Protection Agency issue the regulation around 1980. HP Pavilion dv6-1222sl battery

Inhalation is the second major pathway of exposure, especially for workers in lead-related occupations. Almost all inhaled lead is absorbed into the body, the rate is 20–70% for ingested lead; children absorb more than adults.[85]

Dermal exposure may be significant for a narrow category of people working with organic lead compounds, but is of little concern for general population. The rate of skin absorption is also low for inorganic lead. HP Pavilion dv6-1222tx battery

According to Agency for Toxic Substance and Disease Registry, a small amount of lead (1%) will store itself in bones and the rest will be excreted through urine and feces within a few weeks of exposure. Children have a harder time excreting lead. Only about 32% of lead will be excreted by a child. HP Pavilion dv6-1223eo battery