Ramiel
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Aluminium oxidation via Nitric acid
I have been thinking up a bit of a hairbrained method for Aluminium dust synthesis recently... only I don't think it would work.
First, one alloys solid aluminium with solid copper - perhaps at a ratio of 1:3 for argument's sake.
Then, the alloy is treated with nitric acid...
Al + 3Cu<sub>(s)</sub> + 8 HNO<sub>3</sub> ==> 3Cu(NO<sub>3</sub> <sub>2 (aq)</sub> + 2 NO + 4 H<sub>2</sub>O + Al
In addition to the above reaction, i had hoped that the aluminium would precipitate as a fine dust (just like gold does when low-karat jewlery reacts
with nitric). However, I strongly suspect that the Nitric acid will not just passivate the aluminium powder, but because the Al is so fine, it would
react completely.
Also, i fear that in conc. solutions of nitric acid, the aluminium precipitate would be oxidized.
By now you might be asking... why copper? If you heat it, you get CuO... add CuO to Al in powdered form, and one has a <u>very</u> good
thermite.
Can you just imagine how vigorous the reaction would be with such fine reactants!
Comments? suggestions?
Caveat Orator
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Mumbles
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The concentrated nitric acid wont attack the Al much. It may form a thin layer oxide, but thats it. This is why Aluminum tubing can be used in high
concentration Nitric distillation. <u>However</u> as the copper lowers the concentration of the acid, the acid will begin to attack the
precipitated aluminum. A concentration of lower than 85% attacking aluminum is ringing a bell. To keep above this level, you'd need 6 times the
stoichiometrical amount of Nitric if I figured right. Sulfuric could be added to the mix after the Al was filtered and distill the nitric off.
You'd get some back from the Cupric Nitrate.
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chemoleo
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that is, *if* Cu and Al form a mixable alloy, as not all metals mix!
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Ramiel
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They do, they form a shape memory alloy as a matter of fact. Apparently most such alloys consist of about 20% Al, so I think the alloy i proposed is
plausible.
Thanks for bringing that up though, I hadn't even thought to check.
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Marvin
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Wont work. The resulting Al would be too fine to escape oxidation, even by water, let alone the mixture its formed by. On the bright side with
enough aluminium in the mixture, reacting with NaOH would probably produce a very fine copper powder. A mixture of magnesium and aluminium the same
way might possibly produce fine Mg dust, but here I'm not sure.
[Edited on 6-11-2003 by Marvin]
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