Liquid Mercury Controlled Switch

[Darkness]

I have a switch which is controlled/activated via a reached weight. When the weight is reached, the tube of mercury tilts to one direction causing the mercury to bridge the two contacts.

The problem I have is the glass tube of mercury has had it in regards to, the mercury doesn't fall back to the other side of the tube terminating the contacts so my motor stays on all the time.

Anyone know where to get such replacement mercury filled tubes or is there a new uptodate style of controlled switch?

Cheers.

 

[breezer]

mercury switches were banned years ago.

only suggestion would be a microswich, maplin sell small ones

 

[Darkness]

Didn't know that. The switch has been in for years.

Why the ban on the switches anyhow?

 

[breezer]

because they contain mercury

 

[mapj1]

You can't design them into new consumer equipment, but you can still get them as spares, and also for new use as mail order from some places outside the UK. Search for 'tilt switch'. The modern ones have a plastic body, not a glass one, which personally I think is a shame, I always liked the way they arced over with a purple corona
try here as anexample of the modern sort.
http://www.maplin.co.uk/Module.aspx?ModuleNo=2677&TabID=1&source=14&doy=
what sort of rating do you need, you will almost certain,y have to substitute.
If you think you may manage to break the old one when removing it, have some flowers of sulpher handy to mop up any spillage, and dont' breath the vapour - the liquid itself isn't that poisenous, its the vapour that gets to you after while, and prolonged exposure affects neural functions and casues you to go mad, hence 'mad as a hatter' the victorian hatters used mercury to flatten felt onto card board, squeezing out bubbles from the glue joins. In true victorian tradition the effect was well known, but instead of trying to reduce it by mitigation measures, they made it a thing to joke about. So remove the old one with care in a well ventilated space.

 

[ban-all-sheds]

its the vapur that gets to you after while

prolonged exposure affects neural functions

Darkness - I don't think you're in much danger from a few whiffs of vapour if you do break it. But if you do you will need to find a way to clear it up - kitchen roll or J-cloths won't work...

Also you're not supposed to toss the old one in the bin, as it's toxic waste.

 

[Darkness]

I rang a relative who I forgot about, who works for one of Britains+Europes biggest glass production companies. He's an electrician there who works with automatic switches etc all the time.

He said he should have one for me very soon thats if he finds a mercury tube of the same size but he said he has quite a few to choose from.

 

[big-all]

in regards to removing the mercury when spilt i would assume ice cubes would bring it to its solid state although i am not exactly shure at what temperature it changes to a solid

 

[Panjandrum]

Mercury freezes at -39 degrees C.

 

[big-all]

aaaaahhhhh liquid nitrogen then
and brittle carpets at the same time

 

[breezer]

we wont mention brittle fingers then.

seen an apple dipped in liquid nitrogen, it was then hit with a hammer, shttered just like glass

 

[big-all]

we wont mention brittle fingers then.

seen an apple dipped in liquid nitrogen, it was then hit with a hammer, shttered just like glass

well yes breezer frozen assests all round

 

[Darkness]

aaaaahhhhh liquid nitrogen then
and brittle carpets at the same time

Well that is ok cause I've a tank of the stuff. Good for taking warts off.

 

[felix]

To get back to the subject ---

Darkness, you are in minimal danger from spilt mercury. It's soluble mercury compounds that are poisonous. Those hatters went mad from exposure to mercury nitrate. The metal itself is safe enough to be used for filling teeth. I've got more mercury than tooth in some of mine. The vapour pressure of mercury at room temperature is also very low indeed. If it wasn't, the mercury diffusion vacuum pump would never work.

The only thing that might worry me is if I saw some non-metallic deposit on the surface of the stuff. I would certainly wash my hands after touching that.

PS: I remember a standard school physics experiment with a toothed copper disc dipped in mercury and spinning between the poles of a magnet. An impressive shower of sparks flew from the teeth as each one cleared the surface, presumably accompanied by a spray of vapourized mercury. The physics teacher, who must have demonstrated this to countless classes, was still alive and compus mentus years after I finished school.

PPS: I expect that old spinning wheel has since been condemned; along with the CV gas thermometer, the radon generator and the diving board.

 

[Darkness]

The problem I have with the mercury is its done if that makes sense. Its liquid and lumpy as if it gone dry/hard. Hard to see exactly but its finished.