Gargamel
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Cleaning contaminated mercury
Well I allways wanted some mercury, which is very hard to get here, and today I had a stroke of luck an got almost a pound from my uncle, who wanted
to throw it away.
Now, this is not a nice Merck bottle, rather a shabby old jam jar, and the stuff is said to come from mercury switches and old thermometers.
It has some dirty skin swimming on, which I failed to decant.
Mercury normally does not make any oxide when exposed to air, or does it?
What kind of procedure would you recommend to purify this stuff?
Sadly I don't have a destillery...
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HgDinis25
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Filtering mercury through cotton ussualy does the trick.
You can get a syringe and fill the tip with cotton. Then add mercury from the other tip, place the piston and press. The piston will force the mercury
through the cotton and out of the syringe, filtered.
The setup goes like that (image not mine):
http://etchings.org/PermeableGrounds/Syringe%20Filter.jpg
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IrC
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Squeezing through chamois was popular with the local mad hatters back in the day. The sham wow guy is never around when you need him.
"Science is the belief in the ignorance of the experts" Richard Feynman
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Gargamel
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Thanks, I'll try that.
If there are other metals dissolved in the mercury, how do I get rid of them?
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HgDinis25
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Thats a bit harder, because most metals won't be dissolved in mercury. They will likely have formed an amalgam. Some amalgams are soluble others
aren't.
The best way to clean it from metals is by adding Hydrochloric Acid. Add the acid and then start mixing it like crazy. The acid and the mercury DO NOT
mix unless you really mix it like a crazy person. Now, DO NOT try boiling it to speed up things. Actually try to keep the temperature low to minimize
mercury vapor evolution and do this in a well ventilated area. HCl will dissolve aluminium, zinc and other metals that would normaly dissolve in HCl.
Mercury won't react. If you do not see any gas evolving then your mercury is clean. If it isn't then it should liverate hydrogen gas from the reaction
of HCl with hydrogen. After the evolution of gas as ended, the acid-water-metal salts will form a seperate layer from the mercury. Just remove the
mercury.
PS: Remember that mercury itself isn't very harmfull but it's vapors are.
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phlogiston
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Supposedly a effective yet simple method for removing floating impurities from mercury is to use a folded paper funnel with a tiny hole in the tip.
Running the mercury through the funnel should remove the floating debris. Haven't tried it myself, though.
-----
"If a rocket goes up, who cares where it comes down, that's not my concern said Wernher von Braun" - Tom Lehrer |
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MrHomeScientist
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I have tried the funnel-with-pinhole method, and it does indeed work. I wasn't able to remove every last bit of the floating crud, but probably 95%
was stuck in the filter afterwards and the mercury surface was much, much cleaner. When transferring mercury, be aware that because it is such a heavy
liquid it can move suddenly and unexpectedly. Always use secondary containment (i.e. big plastic tray) when working with this metal. Also be sure to
properly dispose of the crud-laden filter paper as mercury-containing waste.
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Gargamel
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Hi there,
well yesterday I had some time for my hobbies again, I tried the syringe/cotton and the hole in the filter tricks.
Well there was some succes, but not the breakthrough I hoped to achieve.
Concerning dissolving the impurities with dilluted acid - some people suggest HCl, while the more common method seems to be HNO3.
Since HCl is much easier to come by, I'd prefer that method. Do you have an opinion on that, is there some reason should rather use HNO3?
I don't know what kind of metals are in there, I cannot judge whats more soluble, nitrate or chloride...
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annaandherdad
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HNO3 will dissolve mercury, HCl will not.
Any other SF Bay chemists?
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HgDinis25
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Be careful when mixing reagent s with mercury when you don't know the outcome. Nitric Acid it self reacts with mercury. However, absent high
concentrations or heat, the reaction is very very slow. So if you ever go around that method be sure to neutralize your waste with Hydroxide ions, to
precipitate the less dangerous Mercury (II) Oxide.
Anyway, if you're going to clean with acid, then I expect you already suspect your contamination to be from a metal. My bet would be an Amalgam with
Aluminium. If that's the case, cleaning with HCl should do the trick (don't even think to boil anything to speed up the reaction unless you want some
mercury vapours to laugh at you).
On the other hand, if the contamination comes from silver amalgam, then Nitric Acid should be used. If you got gold amalgam contamination, you're
screwed.
Can you describe a little bit more you're mercury, perhaps take some pics?
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S.C. Wack
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https://www.sciencemadness.org/whisper/viewthread.php?tid=10...
(The guy I bought them from knew exactly why I wanted to buy them, and didn't hesitate a second to say so.)
(Flinnsci does not sell anything mercury now, much less at $29 a pound with no hazmat.)
KMnO4, a milk jug, nitric acid, water, and a large bowl. Nothing more.
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Bert
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There are heavy duty electrical relays/contactors and switches that contain large amounts of Mercury- I have seen these containing over a liter of Hg.
Removed some from obsolete equipment, and found the Hg to be pretty heavily contaminated, likely from whatever arcing took place as contact was made
and broken? It was still good enough for some uses.
Rapopart’s Rules for critical commentary:
1. Attempt to re-express your target’s position so clearly, vividly and fairly that your target says: “Thanks, I wish I’d thought of putting it
that way.”
2. List any points of agreement (especially if they are not matters of general or widespread agreement).
3. Mention anything you have learned from your target.
4. Only then are you permitted to say so much as a word of rebuttal or criticism.
Anatol Rapoport was a Russian-born American mathematical psychologist (1911-2007).
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