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January 23, 2013

The long awaited and overhyped……….Aluminium!

Aluminium was glamorous once. She had a shiny and glittering past that has dulled with the passage of time to become ordinary and everyday. Aluminium metal has a very high reflectance (only outperformed in the visible region of the spectrum by tin and silver) and it forms the silvery reflective surface under glass mirrors. Mirrors made of pure aluminium would be less successful as the surface reacts with oxygen in the air to form a this, dull oxide layer. Al CAKE BallsIt can retain its silvery appearance when its a fine powder which gives it a use in silver paints and even decorative silver cake balls. Worry not, the cake balls are edible and even a whole tub of these would not come close to a dangerous dose of aluminium because it forms such a thin coating.

Aluminium has a chequered past. After many centuries of playing hard to get (the ancient Greeks used aluminium salts) aluminium metal was extracted in its pure form in 1825. The long wait for her arrival was because aluminium is quite reactive. She is quick to latch on to others and then gets quite clingy. Extracting the pure metal is therefore difficult and involves a huge amount of effort and energy. Even modern methods involve huge amounts of electricity used in the process of electrolysis of bauxite (aluminium’s most common ore) making recycling much more efficient.

But once the problems of extraction had been overcome Aluminium burst on to the scene like a glittering starlette. In the 19th century aluminium was novel and precious despite being the most abundant metal in the Earth’s crust. Napoleon III let his most honoured guest use aluminium cutlery while everyone else at the party had to make do with gold. The capstone of the Washington monument is a lump of pure aluminium, chosen because, at the time, it was more valuable than silver. The capstone was even put on display at Tiffany’s before being hoisted to the top of the obelisk.

Today aluminium seems bland and uninteresting because we see it everywhere from cars to rockets and window frames to drinks cans. Although it is difficult to extract the metal from its ore the metal itself is very easy to recycle. Aluminium finds such a wide variety of uses because of its resistance to corrosion and low density. The oxide layer formed with atmospheric oxygen forms an effective barrier  protecting the metal underneath from further corrosion. The metal is malleable and tends to be quite soft in its pure form meaning it has to be alloyed with other metals to give it strength.

In the main Aluminium is functional and everyday though a bit of glamour still clings to this element in the form of jewels. Rubies and sapphires are just aluminium oxide compounds contaminated with either chromium or iron. The trace elements give the gems their colour but it is aluminium oxide that makes up the bulk of the structure.

But there is one last party trick that Aluminium has up its sleeves – impersonations. Get seven aluminium atoms together and they do a passable impression of germanium. Thirteen aluminium atoms stuck together look for all intents and purposes like chlorine and chemical tests won’t be able to tell the difference. These clusters of atoms are known as “superatoms” but they don’t have a cape or fight crime.

Should you wish to worship at the feet of aluminium you can do so in Piccadilly Circus. That statue that looks like a bronze Eros… is actually an aluminium Anteros. True.

Next time on a Periodic Tale it’s Carbon’s slightly less versatile, but no less interesting, cousin Silicon.


Image by @SciCommStudios

  1. Leslie Glasser permalink

    I am sorry if I seem pedantic, but it is better to be right! ”It’s” is an abbreviation for “it is”. The posessive pronoun is “its”, not “it’s”.

    For an entertaining read on the issue, see “Eats, Shoots & Leaves” by Lynne Truss, Profile Books: London, 2003. Leslie Glasser

    >________________________________ > From: scicommstudios >To: >Sent: Wednesday, 23 January 2013, 20:13 >Subject: [New post] Aluminium > > > >scicommstudios posted: “The long awaited and overhyped……….Aluminium! Aluminium wasglamorousonce. She had a shiny and glittering past that has dulled with the passage of time to become ordinary and everyday. Aluminium metal has a very high reflectance (only outperforme” >

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