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Author: Subject: A stirring exception
Sulaiman
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[*] posted on 22-5-2024 at 01:33
A stirring exception


I'm currently planning and testing some purification procedures for mercury.
The first stage is 'washing' the mercury in dilute (c1M) nitric acid.
Agitation (air bubbler, strong stirring) is required to dissolve any base metals, oxygen from the air helps with oxidation of some base metals.

Now the odd part;
The mercury/acid mixture must be agitated continuously,
if not nitrous acid builds up in the vicinity of the mercury and starts to dissolve it!
Mercury consumption by the acid is over 100x slower with agitation!
So stirring/agitation is required to REDUCE the reaction rate.




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charley1957
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[*] posted on 22-5-2024 at 03:23


What an exceptional observation!:D



You can’t claim you drank all day if you didn’t start early in the morning.
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Sulaiman
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[*] posted on 22-5-2024 at 05:23


Not my own observation,
I'm just repeating what I read, and have tried a little;


V H Veley, 1890, "The conditions of chemical change between nitric acid and certain metals"

Attachment: nitric-acid-and-certain-metals.pdf (7.5MB)
This file has been downloaded 8 times

I'm just researching methods of mercury purification that minimise toxic waste generation.

Mentioned just because it's anomalous and probably not commonly known.

[Edited on 22-5-2024 by Sulaiman]




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Precipitates
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[*] posted on 22-5-2024 at 05:44


Please let us know how you get on.

I've got a pound of mercury I would love to clean up at some point (ideally without generating a load of toxic waste!).

I love having it, but the joy is somewhat ruined by how dirty it is.
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Sulaiman
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[*] posted on 22-5-2024 at 06:09


It seems that there are well recognised stages to 'cleaning' mercury;

1) to your mercury add about 1/2 the mercury volume of c1.5M nitric acid (1 part Az. nitric : 9 parts water) in a glass or plastic container.
Agitate/shake violently until you are exhausted,
(your mercury will now be 'shiny')
(the full procedure involves vigorously bubbling air for 24 hours per acid wash, and a few hours per water rinse)
pour off the acid that now contains most of the base metals (toxic),
rinse with water a couple of times.
Repeat the acid wash, rinse with water a few times.
Your mercury will now be beautifully 'shiny', fluid, and leave no 'tails' .

2) rinse with a little acetone to remove moisture and oils/grease etc.
3) mechanical filtering, fritted funnel with vacuum (gravity alone will not force mercury through)
or any other method you like.


Remaining Silver and PGMs can be removed by distillation.
I've not got to this stage yet.

Any PGMs in trace ammounts do not significantly effect the properties of mercury,
and do not oxidise to form 'scum' on the surface of the mercury.
Store dry with as little air/head space as practical.

Apparently if your mercury is completely 'shiny' after months of storage, the base metals contamination is measured in 10's of ppb, not in ppm.

I have c100g Hg heading to me in the post at the moment.
This batch I will try to measure how much base metals contamination there is.
Then add it to the rest of my mercury.
I intend to do a video of the cleaning process of my entire stock (c120ml), including distillation, within a few months.

PS I've read that adding a little peroxide to the acid removes any sulphides.
I've not tried.

[Edited on 22-5-2024 by Sulaiman]




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[*] posted on 22-5-2024 at 06:45


Quote: Originally posted by Sulaiman  

I intend to do a video of the cleaning process of my entire stock (c120ml), including distillation, within a few months.


That would be great!

Quote: Originally posted by Sulaiman  

'scum' on the surface of the mercury..


That's exactly what I've got on my mercury right now sigh :(
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charley1957
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[*] posted on 23-5-2024 at 04:42


I have several pounds of mercury I got from a dentist who was retiring. To that I added some mercury I’d had for years which had a nasty scummy layer on top, some rust and dirt. I finally decided to clean it all up somewhat so I forced it through a cotton ball in the bottom of a syringe. It took a couple of days to do it all that way. It was beautifully shiny after that, and I just stored it under some distilled water in a glass jar, which is inside of a plastic jar. Years later it is still just as pretty as it was back then. Don’t know what metals may be dissolved in it if any, but I’m content with it the way it is. If I need really pure mercury I guess I can distill the amount I need.



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