kazaa81
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Catalyst for Aluminium ethylates synthesis
Hallo to all,
I've found in a patent that aluminium ethylate can be synthesised by boiling aluminium (foils, powder...etc) in ethyl alcohol in presence of a
mercury salt, in this case, HgCl2 (mercury chloride).
Does anyone know another catalyst for this reaction, if possible not mercury, chromo compounds?
Thanks for help 
[Edited on 9-11-2004 by chemoleo]
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neutrino
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I've heard of mercury I compounds being substituted for mercury II compounds. Hg<sub>2</sub>Cl<sub>2</sub> is somewhat
less toxic than HgCl<sub>2</sub>, although there are still those (like me) who wouldn’t touch it with a long pole anyway. Hope that
helps.
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chemoleo
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Hmm, i would have thought it doesn't matter which oxidation state of mercury one uses, as Hg+/(2+) + Al --> Hg + Al(3+).
The resulting Hg reacts with the aluminium, forming aluminium amalgamate, and thereby exposes the aluminium, enabling it to react with the ethanol.
I.e. normally the Al is protected by a tough Al2O3 layer, which makes it resistant against H2O and ethanol. But not, if the the layer is crumbled
during the amalgamation process.
This is why the reaction works I suspect. However, I don't think there are other metals you could substitute Hg with.
Of course, you can use mercury itself (not a salt), a tiny amount from an old Hg-thermometer should suffice. Oh, and Al /grains would be presumably
better too.
PS Oh, another idea to confirm this - add a small amount of acid or base (HCl/NaOH), preferably NaOH, as it will react with the Al2O3 forming
aluminates.
This may remove the protective layer of Al2O3, enabling it to react with EtOH. So- dissolve some NaOH in EtOH, and react it with Al powder (boil it).
That may have a chance to work.
PS2 What's the patent number kazaa?
[Edited on 9-11-2004 by chemoleo]
Never Stop to Begin, and Never Begin to Stop...
Tolerance is good. But not with the intolerant! (Wilhelm Busch)
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Tacho
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Chemoleo, maybe if Hg2Cl2 is slightly soluble in alcohol, it would be a safer Hg source than mercuric chloride.
I believe neutrino is refering to the fact that Hg2Cl2 (calomel, mercurous chloride) is so insoluble in water that it was used as a purgative (yes,
people ate it as medicine) until a few decades ago. It is certainly orders of magnitude safer than mercuric chloride.
In my experience, the reaction of Al powder and aqueous NaOH (EDIT:sorry, I meant HCl, but I bet NaOH can also be violent) is a runaway,
exothermic-to-uncontrolable-boiling kind of reaction. It has scared me. I have heard that amalgamation may produce similar results. Be careful.
[Edited on 10-11-2004 by Tacho]
[Edited on 10-11-2004 by Tacho]
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chemoleo
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Sure - but the point is, you arrive at Hg as an element regardless, in the form of an Al-amalgamate.
As to adding NaOH- I meant catalytic amounts, only i.e. 1/20th of the stoichiometric amount of Al - done so just to ensure that the
oxide layer is removed!
Alternatively, just add a large amount of NaOH to Al chunks/sheets, until the reaction becomes violent. Then wash it (keeping it always under water),
and add your ethanol. That way, you digested the oxide layer, then removed NaOH/aluminates, and react the exposed oxide-free aluminium straight with
EtOH.
Never Stop to Begin, and Never Begin to Stop...
Tolerance is good. But not with the intolerant! (Wilhelm Busch)
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Organikum
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Using Al-powder is not good. This needs much to much Hg-salt and the reaction gets very exothermic and hard to control. Too much surface area.
I would recommend Al-sheet or thick Al-foil crumbled to small balls.
Only tidy amounts of Hg-salt are needed, the reaction takes longer but that doesnt really matter, better than having the shit jump out of the flask.
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Tacho
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Hg2Cl2 does NOT work for aluminum amalgamation.
I tried it.
I tried to boil it with some conc. HCl , then neutralize the acid with NaCO3. This brought no improvement: ZERO reaction with Al foil.
So if you want Al amalgam, you must die of Hg poisoning. Could anyone attach the MP3 of Monty Phython`s "Look at the bright side of life..."
Just kidding, the MP3 would be too big, Polverone would be pissed off.
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kazaa81
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Question.....
Hallo to all,
first, thanks at all for the useful infos!
Tacho has posted by his personal experience that Hg2Cl2 doesn't work for aluminium amalgamation.
At this point, are we sure that reaction betwen ethyl alcohol and Al (+heat) starts for the formation of an Al/Hg amalgama?
In this case, I think, would be another catalyst....or can the reaction start without catalyst?
Thanks at all!
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Tacho
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Hg2Cl2 + Calcium hipochlorite (pool bleach), DOES react with Al to turn its surface to a dark gray, like if it was covered by zinc powder, I presume
that`s amalgamation.
I put a tiny bit (a spatula tip) of each in a test tube, some drops of water, heated it a bit, poured more water to complete 30ml added the Al strip.
Half hour later it was dark.
Hg2Cl2+H2SO4+H2O2=failure.
Huge edit:
By the way,
1) I moved the gray Al strip to ethanol, so I could discart the Hg solution. Is there any easy test to do to this gray Al, to check if it's
amalgamated? Please, no drug linked sugestions.
2) I mixed the Hg solution with lots of Zn powder, so that Hg gets reduced and than amalgamated with the excess Zn to some sort of dental-amalgam like
thing. Does anybody sees a huge flaw in this method of discarting this small amount of Hg ions?
[Edited on 15-11-2004 by Tacho]
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chemoleo
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I tried to remove the oxide layer with KOH as suggested above. After about 20 litres of H2 evolution (joke - it's been lots of bubbles though),
using normal Al foil, this was diluted with lots and lots of water, until it stopped bubbling. The water was decanted , and to this absolute EtOH was
added, then it was shook up, and repeated, to ensure that very little water would be left.
This I boiled on a hot plate for a while, and indeed, bubbles came off the Al! However, very tiny ones compared to with KOH straight.
So I am not sure what this is, whether it's a leftover from KOH causing this, or truly the EtOH. It was noteworthy that the bubbling only began
at higher temps. If this works with KOH/ethanol, it's VERY slow.
Tacho - alternatively, to remove the Hg, you could always add some NaSx, or boil it with sulphur itself - making red HgS, which is insoluble (and
supremely unreactive) and can thus be filtered off.
Never Stop to Begin, and Never Begin to Stop...
Tolerance is good. But not with the intolerant! (Wilhelm Busch)
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Tacho
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Just for the record.
Hg2Cl2+Calcium hypochlorite mix does not make a piece of copper become silvery (thanks Polverone), so it's unlikely that the darkening of Al
strip was due to amalgamation.
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