MR AZIDE
Hazard to Self
Posts: 64
Registered: 21-5-2012
Location: UNITED KINGDOM
Member Is Offline
Mood: Fizzing
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HgCL2 displacement reaction.
I happened to have some mercuric chloride, in a mish mash box of samples .......
Not very soluble in water, and very heavy lumpy/cakey crystals.
Addition of some Al foil, is a nice reaction to watch.
If the Al foil is pressed against the glass of the beaker, the first thing you see is the Al foil go grey, as incredibly fine globules of Hg form.
As more Hg forms, it starts to amalgamate with the Al, and the surface of the Al has this amazing visual effect ,as if the Al foil is melting, and
is shimmering.
small holes appear in the foil, and it eventually becomes heavy and sinks down in to a little globule of Al amalgam, further Al foil seems to
miraculously disappear into the globule increasing its size.
Once all the Hg is displaced the remaining Al foil, ( with its Oxide removed) reacts fairly quickly with the solution, and the solution goes grey due
to impurity and Al(OH)3 forming.
The Hg can be recovered, by rinsing all the grey crap away, and placing the Amalgam in a conc NaOH soln........the Al dissolves away out of the
mercury., ( more slowly than if it was Al on its own) and the globule gets more reflective, and more mobile.
Leaving overnight,. the mercury is visible the next day.
Most displacement reactions ive done like this, usually leave the lower metal as a fine, but not very recognizable powder, This reaction has some
nice visual effects, and the precipitated metal is instantly recognisable for what it is.
How availible is Mercuric chloride nowadays. I wonder???
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Hexavalent
International Hazard
Posts: 1564
Registered: 29-12-2011
Location: Wales, UK
Member Is Offline
Mood: Pericyclic
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Usually, not very widely available at all, mainly due to concerns with toxicity - mercury salts are more toxic than the metal itself. Most people who
have it either have purchased it from a speciality supplier, synthesised it themselves or somehow acquired an old sample off websites like eBay (under
very special conditions and very rarely!) or from somebody they know, for example.
"Success is going from failure to failure without loss of enthusiasm." Winston Churchill
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