Getting air out of a mercury barometer?

Hi folks,
Does anyone here have experience of getting the air out of a mercury barometer column? My barometer looks like this:
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I had wondered about putting the whole barometer in a vacuum chamber, but I'm not sure if this will work. Unfortunately there's nowhere to connect a vacuum pump at the top of the column.
Is there anyone with experience here who can give me some tips? So far, I've been trying to avoid taking the barometer apart in case I lose the precious (and slightly dangerous) mercury.
The amount of air inside is enough to change the reading by 10 to 20 mm.
Best wishes,
Chris
Reply to
Christopher Tidy
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My German isn't quite good enough to fully translate section 5, Wartung.
Reply to
Jim Wilkins
...
Same here ... however, copy/paste into Google Translate gives ok results: "5. Maintenance \ Because of the unhindered air access, the mercury level in the lower vessel oxidizes over time. If the oxidation has progressed so far that the tip of the scale can no longer be reliably adjusted to the lower mercury level, the mercury in the vessel should be removed from the barometer and cleaned. \ CAUTION! \ The mercury may only be cleaned by qualified specialist personnel."
A couple of other places talk about sending it in for repair; eg at the end of section 3, "If it is not possible to remove any air bubbles that are in front of the air trap or if air has entered the vacuum chamber, the device must be sent in for repair."
Interestingly, the last paragraph about mercury barometers in says, "On June 5, 2007, a European Union directive was enacted to restrict the sale of mercury, thus effectively ending the production of new mercury barometers in Europe."
Reply to
James Waldby
Maybe not worthwhile but there are mercury replacement alloys
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Reply to
David Billington
James Waldby on Thu, 5 Mar 2020 07:54:24 -0000 (UTC) typed >> "Christ>>> Does anyone here have experience of getting the air out of a mercury
That is boilerplate to protect the company. "As Everybody knows" touching mercury results in your instantaneous poisoning, tremors, brain damage, and voting to leave the Glorious EU.
Reply to
pyotr filipivich
James Waldby on Thu, 5 Mar 2020 07:54:24 -0000 (UTC) typed in rec.crafts.metalworking the following:
Aha! Bwahahahaha.
This is the metal working group, yes?
So of course, check out Cinnabar.
All you have to do is crush the ore and roast it.
"The process of extraction of the mercury is relatively simple. An oxygen furnace can be used to heat up the ore cinnabar and condenses the fumes of mercury released from the process."
Better than buying the stuff in a store, and "you made it yourself!"
Reply to
pyotr filipivich
The standard procedure is to turn it upside down, use an eyedropper to fill the bottom of the tube, and poke a wire down the column to knock any air bubbles loose. Then, the TRICKY part is to get the tube back right- side-up without allowing the mercury to escape and air to get back in.
It seems impossible to do this without getting your hands in the mercury.
Jon
Reply to
Jon Elson
It could well be legalistic boilerplate. However, I think there are two issues with air in the barometer. Section 3 (which got snipped) is about trapped bubbles of air. Section 5 is about oxidized mercury, which apparently is fairly toxic.[1] [1]
Pulling a vacuum on the mix of mercury and mercury oxide - if that's what's in the barometer and causing problems - wouldn't remove the HgO, I think. HgO is about 2/3 as dense as Hg so would expand the volume when present. Christopher, is that consistent with the symptoms?
Reply to
James Waldby
Is there any legal way to ship small amounts of Mercury? I have about a dozen mercury switches from old wall thermostats.
Reply to
Michael Terrell
I think nitrile gloves will work just fine to keep mercury from touching your skin. As long as it is not methyl mercury. A drop on a rubber glove will still kill you. Slowly. Like in a few weeks. Eric
Reply to
etpm
Try holding the mercury barometer on its side or to the point where the air can pass to its neutral state, while rotating it as it comes together etc, like water in a glass tube
Reply to
paulgansett
The wire and eye dropper are neat ideas. The problem is getting the reservo ir back over the end of the column while the whole thing is in the inverted position. The reservoir is glued together, and I wonder if originally the column was filled first, then the bottomless reservoir was mounted and fill ed, and finally the bottom of the reservoir was glued on. But I'm reluctant to try and dismantle the reservoir. I think I might damage it.
Never did me any harm in the past.
Chris
Reply to
Christopher Tidy
er%20604%20Bedienanl.pdf
There's a little oxide in there, but the main problem is that the barometer lay flat for years and was shaken around during a move.
Chris
Reply to
Christopher Tidy
e air can pass to its neutral state, while rotating it as it comes togethe r etc, like water in a glass tube
I've tried this. It seems that the reservoir is unfortunately too large (co mpared to the volume of mercury) for this to work.
Chris
Reply to
Christopher Tidy
Interesting, but the density would be wrong for the barometer.
Chris
Reply to
Christopher Tidy
Thanks for all the responses. I'm pondering the vacuum pump idea. Can anyone see a reason why I shouldn't put the barometer in a vacuum chamber (and then probably lie it down and bring it back to the vertical to remove the last traces of air)?
Or connect a pump directly to the reservoir (so long as I make sure the mercury can't go into the pump)?
Chris
Reply to
Christopher Tidy
Exhaust the pump out of doors? Vapor pressure of Hg at room temp is not negligible so as you approach vacuum, you're sucking and exhausting more and more Hg molecules.
Just a thought...
Reply to
Mike Spencer

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