Getting air out of a mercury barometer?

My German isn't quite good enough to fully translate section 5, Wartung.

...

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

Maybe not worthwhile but there are mercury replacement alloys

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.

James Waldby snipped-for-privacy@valid.invalid 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!"

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

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?

Is there any legal way to ship small amounts of Mercury? I have about a dozen mercury switches from old wall thermostats.

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

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

Am Donnerstag, 5. März 2020 22:55:51 UTC+1 schrieb Jon Elson:

The wire and eye dropper are neat ideas. The problem is getting the reservoir 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 filled, 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

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

Am Freitag, 6. März 2020 03:29:19 UTC+1 schrieb snipped-for-privacy@gmail.com:

I've tried this. It seems that the reservoir is unfortunately too large (compared to the volume of mercury) for this to work.

Chris

Am Donnerstag, 5. März 2020 13:25:47 UTC+1 schrieb David Billington:

Interesting, but the density would be wrong for the barometer.

Chris

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

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...