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Chapter 15: Modern Metals


Aluminium is a metal element, symbol Al, atomic number 13.

Aluminium is used more than any metal except iron. Aluminium is the most abundant metal element in Earth's crust (8.16% by mass), and is only exceeded by the non-metals oxygen and silicon.

Aluminium attribute Makes it suitable for
Light weight metal - can be made very strong by processing and by alloying

Vehicles and vehicle parts, such as the bonnet on some new Subaru cars, and alloy wheels. (Note that true "mag wheels" are magnesium, not aluminium, and weigh even less than aluminium alloy wheels.)
Construction, eg window frames.

Malleable (can be made into thin sheets)

Aluminium foil, which has replaced tin foil in common usage such as cooking.
Drink cans.

Ductile Wire.
Very electrically conductive - 4th behind silver, copper, and gold (in that order). The next most conductive element is tungsten, which is almost exactly half as conductive as Al.

Wire, electronics, electrical transmission lines.

Copper is more conductive than aluminium but also heavier and more expensive.

Very thermally conductive - 5th behind diamond (carbon), and once again, silver, copper, and gold (in that order).


Excellent reflector of visible light - about 99%
Good reflector of infrared - about 95%

Mirrors (by vacuum deposition). Such mirrors will not deteriorate like silver mirrors will.
CDs and DVDs (super purity aluminium, at up to 99.999%).



Although aluminium is quite reactive it forms a protective oxide coating, which stops further corrosion. Mercury and some other chemicals remove the oxide coating, which is why mercury is not allowed on aeroplanes, which are made mostly of aluminium.

Antiperspirants use one of a family of aluminium compounds called aluminium chlorohydrates to clog sweat glands, normally Al2Cl(OH)5.

Water purification uses other aluminium chlorohydrates, particularly Al12Cl12(OH)24 due to the pH of that molecule.

Production of aluminium became easy after electrolysis was discovered, and the price of aluminium decreased hugely. However, according to Wikipedia it was once considered a precious metal more valuable than gold. Napoleon III, Emperor of France, is reputed to have given a banquet where the most honoured guests were given aluminium utensils, while the other guests had to make do with gold ones.

Recycling aluminium (eg, melting down old drink cans) uses only 5% the electriciy that smelting new aluminium from ore does. New Zealand has an aluminium smelter at Tiwai Point at the entrance to Bluff Harbour. From their web site: At 99.98% pure, NZAS produces the highest purity aluminium in the world. Most of the aluminium it produces is exported, with Japan and Korea the biggest buyers. In 2004, NZAS generated a total export revenue of NZ$1 billion.

Warning: Their "Operation" info page has a 5MB mugshot of their boss on it. Grrr. I've told them about the problem and two weeks later they still haven't done anything about it.


Spelling of this metal's name basically depends on country. The New Zealand spelling is aluminium. For historical reasons the American spelling is aluminum (with the emphasis on the second syllable instead of the third). Humphrey Davy used alumium in 1808, and aluminum in 1812, but in the same year the Brits figured out that aluminium matched many other elements and they thought it sounded more classical. Wikipedia says In 1926, the American Chemical Society officially decided to use aluminum in its publications ... The International Union of Pure and Applied Chemistry (IUPAC) adopted aluminium as the standard international name for the element in 1990.

Aluminium oxide

Aluminium oxide or alumina (Al2O3) makes up 15.41% of the mass of Earth's crust. See the table under Earth's crust on the chapter 14 page. It is normally found as bauxite, a red-coloured ore that gives outback Australia its characteristic colour. Bauxite is made of a mix of Al2O3, Fe2O3 (rust), and SiO2.

Aluminium oxide is found in crystaline form naturally as corundum (rubies and sapphires), emery, and is used in glass making. The colour in rubies (red) and sapphires (other colours) come from impurities - for example chromium, which gives a red colour. (A Cr3+ ion replaces the occasional aluminium ion.) Some watches have sapphire watch glasses. Because of their hardness they are very resistant to scratches. Corundum is used in industry as an abrasive.

Lasers can be made using rubies and sapphires. The first laser made (in the early 1960s) used a ruby. Synthetic ruby and sapphire are used in lasers for the production of coherent light.


Triuranium octaoxide (U3O8) has a molar mass of 842.1g/mol (or a molecular mass of about 842 atomic mass units). It has a density of 8.3 g/cm3. Also called uranite. It is a green to black, odourless solid, and is the most stable of the uranium oxides.

The yellow uranium oxide mentioned in the book is UO3, and a black oxide also exists, UO2, which is also called pitchblende.