Sciencemadness Discussion Board

Mercury Switches

Abromination - 8-8-2018 at 21:45

As many of you probably know, some older thermostats contain mercury switches. The switch consits of a glass ampule under vacuum with about 5 grams of mercury and two electrodes. When the switch is turned, the mercury flows to complete the circuit between the two electrodes.
What I want to know is how to get my hands on one.
Does anyone know how to tell the difference between a mercury thermostat and a plain electrical one (obviously they are both electrical, but you get the point.) An obvious hint is whether or not it is digital, but that only rules out so much.
Also, how do you get to the mercury ampule, and is it safe to open it? If so I would assume that I would jusy score the glass with a fule and break the top with a hammer.
Easiest way for me to get it, don't ask why ;)

NeonPulse - 8-8-2018 at 21:57

For small switches I have used wire cutters to break the glass and pour out the contents but for larger ones with no glass excess where it was sealed it’s easy to break them in a container and just have the glass float on the Hg which can be removed with a strip of duct tape after removing the larger parts of it.

Vosoryx - 8-8-2018 at 22:37

I got a bunch from the local heating and cooling company that they had lying around. Legally they couldn't but I guess they were nice. And it probably saved them a bunch of money.
I crack the top off with a pair of pliers and then pour it into a syringe with a bit of cotton wool at the bottom. Do it to all the ones I have, and then insert and push down the plunger. This filters the glass out.

woelen - 8-8-2018 at 23:23

The switches can be purchased very cheaply from eBay:

https://www.ebay.nl/itm/10-pcs-6mm-Mercury-Switch-Angle-Tilt...

This is just an example, there are many many more. There are bigger ones and smaller ones.
I purchased 100 of these. It's a nice source of mercury and you can break one at a time, giving you half a gram or so of mercury.

DavidJR - 9-8-2018 at 03:21

I suppose it's just like buying it in ampules. Think I'll order some of those...

woelen - 9-8-2018 at 03:51

:D Most mercury per dollar:

https://www.ebay.nl/itm/10pcs-Mercury-Tilt-Switch-0-8A-20V-P...

I just ordered these myself. Each of the switches contains a nice big drop of mercury for less than 3 dimes. This kind of switches makes mercury chemistry accessible for nearly all of us. Even a less desirable financial situation need not prevent you from doing experiments with this.

Be careful though. If you dissolve mercury (e.g. in nitric acid), be aware of the toxicity of the resulting solutions and of the aerosol which is formed from the bubbles when the mercury is dissolved!


[Edited on 9-8-18 by woelen]

Plunkett - 9-8-2018 at 05:02

Mercury contactors or mercury displacement relays are better source than tilt switches if you want more than a few grams of the metal. I bought one for ten dollars that had fifty grams of mercury in it. The best way I found to open the relays was with a pipe cutter and pliers over a tub.

https://www.ebay.com/sch/i.html?_from=R40&_nkw=mercury+c...

Abromination - 9-8-2018 at 07:07

Quote: Originally posted by woelen  
:D Most mercury per dollar:

https://www.ebay.nl/itm/10pcs-Mercury-Tilt-Switch-0-8A-20V-P...

I just ordered these myself. Each of the switches contains a nice big drop of mercury for less than 3 dimes. This kind of switches makes mercury chemistry accessible for nearly all of us. Even a less desirable financial situation need not prevent you from doing experiments with this.

Be careful though. If you dissolve mercury (e.g. in nitric acid), be aware of the toxicity of the resulting solutions and of the aerosol which is formed from the bubbles when the mercury is dissolved!


[Edited on 9-8-18 by woelen]


Thanks, woelen I think Ill get those.
Also, your link brought me to ebay in dutch ;)

Im just planning on adding the mercury to a collection, and maybe adding a few of the switches to my electronics lab.