Sciencemadness Discussion Board

Mercury from Vacuum Tubes

ScienceHideout - 19-8-2012 at 17:19

Hey!

I was thinking about vacuum tubes and how I have a whole box of them in my closet. You can get a substantial amount of mercury from one of them- much more than a light bulb...

I was just wondering how I could get the mercury out. It is in vapor phase in a near vacuum- I would imagine it would be hard to condense- but if I just break it I can imagine it being like a genie lamp :-). I was thinking maybe to break it underwater? I can then just do a liquid-liquid extraction.

Do you think breaking it underwater is a good idea, or is there something better in mind?

P.S.- just to let you know I have 50 vacuum tubes. I do not intend on breaking all of them just to get mercury- I just want a couple more grams to experiment with. Besides- I am sure that keeping the mercury from these bulbs in liquid form is much safer than keeping bulbs of mercury gas! :)

Thanks in advance!

Funkerman23 - 19-8-2012 at 17:46

Are these type 83 tubes or the larger industrial tubes? you'd make more leaving any 83 whole as tube technicians & guitar nuts will pay for them. As for your original post you are going to be dealing with a lot of surface loss. under water might work but there isn't as much mercury in them as some would have you believe. try ignitrons or " octopus "( http://www.holoscience.com/wp/wp-content/uploads/2007/04/Mer... ) mercury rectifiers( although good luck finding one of those, I've been hunting one for 3 years now for the collection)

ScienceHideout - 19-8-2012 at 18:03

Quote: Originally posted by Funkerman23  
Are these type 83 tubes or the larger industrial tubes? you'd make more leaving any 83 whole as tube technicians & guitar nuts will pay for them.


I've looked up some of the tubes on ebay- most of them are worthless :-)

I got the whole box for $5 though... they are the type for televisions :D

barley81 - 19-8-2012 at 18:07

You mean cathode ray tubes? Or are they thermionic valves that are supposed to be used in televisions (which I think you meant)?

Still, you may be able to sell them at a higher price. Take a look at http://www.vacuumtubes.net/mission.htm to see if they're really worthless.

I don't think that it's worth cracking them open to get mercury out. You will certainly contaminate your working area with mercury vapor/tiny droplets if you open them. Also, vacuum tubes contain small amounts of reactive metals (barium is common) to remove all oxygen/nitrogen in the tube.

[Edited on 20-8-2012 by barley81]

Dr.Bob - 19-8-2012 at 18:15

I don't think you will find enough mercury in the tubes to make it worth the trouble breaking them. If you look around you can find old mercury switches, thermostats, and older 40 watt tube fluorescents. I used to have globs of stuff with Hg in it. Even if they appear useless, they would be fun to play with and great in case of a nuclear war, after the EMP. The biggest problem is that shipping mercury is hard to do legally now.

ScienceHideout - 19-8-2012 at 18:20

http://periodictable.com/Items/080.19/index.html

^^ this is very similar to my tube... I've seen pictures of them with even more mercury!

I do not have a cathode ray tube... mine are for the audio, like these:
http://www.ebay.com/itm/1-VINTAGE-ETCHED-BASE-MAJESTIC-G-24-...
or:
http://www.ebay.com/itm/1-VINTAGE-GE-GENERAL-ELECTRIC-12AH7G...

Funkerman23 - 19-8-2012 at 19:30

Quote: Originally posted by Dr.Bob  
I don't think you will find enough mercury in the tubes to make it worth the trouble breaking them. If you look around you can find old mercury switches, thermostats, and older 40 watt tube fluorescents. I used to have globs of stuff with Hg in it. Even if they appear useless, they would be fun to play with and great in case of a nuclear war, after the EMP. The biggest problem is that shipping mercury is hard to do legally now.
Only thing to add to that ( regarding EMPs ) is that unless you use an all tubed design keep a( or a few) spare set(s) of Solid state components in copper foil. is is critical that the foil completely encase what you are trying to save. Look up Faraday cage for those of you wondering what I mean.

DerAlte - 19-8-2012 at 20:37

Where on earth did you get the ridiculous idea that thermionic tubes contain Mercury? It’s about the last thing you want in such a device. It isn’t called a vacuum tube for nothing. The vacuum is maintained by getter materials such as Ba, even Cs etc. That gives the silver mirror you often see. If air/oxygen gets in this goes white. Hg in a tube causes ionization which is just what you do not want! With rare exceptions (mercury arc rectifiers - there's a pool in those -, thyratrons), the level of Hg in electronic tubes in less than the average house or ambient air. There is a small bit in fluorescent light tubes because there you rely on the ionization of Hg to produce blue/UV radiation, converted by the coating to the visible spectrum. And there isn't a worthwhile quantity in those. Thermostats and mercury switches are your best bet - or an antique barometer, or a doctors BP manometer..

Der Alte

Endimion17 - 20-8-2012 at 01:13

If you can't see any mercury inside, you sure won't get any out of it. :D

As DerAlte sait, it isn't called a vacuum tube for nothing. :D

Mercury

Motherload - 26-8-2012 at 18:53

If you are looking for any decent quantity of Hg .... you will have to look for and pick up old thermostats with Hg switches ... if you need a few grams.
If you need an ounce or more ... Go to a firearms store and pick up a "Mercury Recoil Reducer" ... Gunsmiths bore out the stocks of rifles and shotguns and epoxy a 3/4"X4" sealed cylinder filled with Hg for customers who want to tame the recoil of their firearm.

unionised - 27-8-2012 at 04:16

Quote: Originally posted by DerAlte  
Where on earth did you get the ridiculous idea that thermionic tubes contain Mercury? It’s about the last thing you want in such a device. It isn’t called a vacuum tube for nothing. The vacuum is maintained by getter materials such as Ba, even Cs etc. That gives the silver mirror you often see. If air/oxygen gets in this goes white. Hg in a tube causes ionization which is just what you do not want! With rare exceptions (mercury arc rectifiers - there's a pool in those -, thyratrons), the level of Hg in electronic tubes in less than the average house or ambient air. There is a small bit in fluorescent light tubes because there you rely on the ionization of Hg to produce blue/UV radiation, converted by the coating to the visible spectrum. And there isn't a worthwhile quantity in those. Thermostats and mercury switches are your best bet - or an antique barometer, or a doctors BP manometer..

Der Alte

He probably got the idea from looking at a tube like this one
http://periodictable.com/Items/080.19/index.html
which has mercury in it. (I'm assuming Theodore Gray knows mercury when he sees it)
I suspect that, if he does have one like that, it's worth more as a collectors item than the mercury. It's a weird tube Leybold Heraeus are noted for making vacuum pumps etc
rather than tubes.