Looking for info on old, unlabeled Geissler tubes

[ADrake]

TL;DR

ID of gases in Geissler tubes from 1964-1965.

I've been searching for a way to ID the gases in a set of old (1964-1965), unlabeled Geissler tubes at our school. We have no good way of trying to light them anymore. They are in the original, numbered cardboard tubes but have no other identifiers. It seems like we should be able to match the shapes to a gas but I haven't had luck finding a key for that. They do contain uranium glass. Can anyone help us out?

 

[berkeman]

Welcome to PF.

Can you upload a few pictures of these tubes? Use the "Attach files" link below the Edit window to upload PDF or JPEG files. Thanks.

 

[berkeman]

Once we have the pictures and any other info, we can page @dlgoff

 

[Vanadium 50]

If you could light them, you could look at their spectra. If you can't light them, what do you want to use them for?

 

[Baluncore]

https://www.ebay.com.au/sch/i.html?...32023.m570.l1313&_nkw=+Geissler+tube&_sacat=0

Google Images "geissler tube"

 

[berkeman]

Google Images "geissler tube"

Oh wow!

http://steampunkworkshop.com/geissler-tubes/#google_vignette

 

[ADrake]

TL;DR Summary: ID of gases in Geissler tubes from 1964-1965.

I've been searching for a way to ID the gases in a set of old (1964-1965), unlabeled Geissler tubes at our school. We have no good way of trying to light them anymore. They are in the original, numbered cardboard tubes but have no other identifiers. It seems like we should be able to match the shapes to a gas but I haven't had luck finding a key for that. They do contain uranium glass. Can anyone help us out?

 

[ADrake]

TL;DR Summary: ID of gases in Geissler tubes from 1964-1965.

I've been searching for a way to ID the gases in a set of old (1964-1965), unlabeled Geissler tubes at our school. We have no good way of trying to light them anymore. They are in the original, numbered cardboard tubes but have no other identifiers. It seems like we should be able to match the shapes to a gas but I haven't had luck finding a key for that. They do contain uranium glass. Can anyone help us out?

If you could light them, you could look at their spectra. If you can't light them, what do you want to use them for?

Honestly, mostly I'm just curious. However, if I need to dispose of them properly I'll need to know. I intend to use them to demonstrate radioactivity for my 9th graders this year. If we can safely keep them at the school, I'll probably continue to use them for earth science and astronomy as "Hey, look at what this cool old thing could do!"

 

[ADrake]

Welcome to PF.

Can you upload a few pictures of these tubes? Use the "Attach files" link below the Edit window to upload PDF or JPEG files. Thanks.

Thank you. Sorry it took so long to get this updated! The first week of classes gets busy.

 

[Vanadium 50]

Why would these tubes be radioactive?
And if you can't turn them on, how do you demonstrate them?

 

[ADrake]

Why would these tubes be radioactive?
And if you can't turn them on, how do you demonstrate them?

The greenish colored glass contains uranium. I can't demonstrate these particular ones as they were meant to be used but can use online images and use the newer single gas bulbs to show the spectral lines when we discuss electron motion and emission spectra. I for now, I'll demonstrate how our Geiger counter reacts to various materials.

 

[Vanadium 50]

I can't demonstrate these particular ones

So, if we were able to tell you (somehow) what gas is in the tube, it wouldn't really help. Apart from everything else, it's filled with gas - probably less than a gram.

If you want radioactive things, go with the classics: lantern mantles, thoriated welding rods, salt substitute/road salt, etc. Fiestaware is not so easy to find these days, and granite countertops - even scraps - can get expensive. I would not be messing with tubes you can't light.

You should also look into a program called QuatkNet, where you will have the opportunity to build a detector suitable for cosmic rays, with an elementary coincidence circuit. Most people don't understand that a major source of natural radioactivity is the sky.

 

[Bonkers]

1) it's common for gas discharge tubes to have a radioactive component, it helps them to strike at a lower voltage - see wikipedia on neon bulbs which use Krypton-85. In this case they don't want the extra spectral lines, and have used doped glass.

2) Can't get them to light? - try cranking-up the HT voltage towards 10kV, 20kV even, if you dare.

3) Make sure there is a (HV-rated) series resistor to limit the current to [1-10mA].

4) or use a string of resistors to meet the HV spec, you could go 2x over the rated voltage, per resistor, for infrequent and monitored usage.

5) build the resistor string in mid-air, no substrate, PCB, paxolin or anything.

6) be bloody careful - but hey, you are a physics teacher and should know HV experimental safety

Even if the tubes have gone a bit "soft", you should still see something. If they've leaked all their vacuum to ambient pressure then they'll never light, but may find use as a Geiger source. As a last-ditch attempt, maybe try them with a Van de Graaf generator or a Tesla coil - with resistors and behind safety glass.

 

[tech99]

I don't think a Van de Graaff will require a limiting resistor as the current is only a few microamps maximum. It is also possible to buy a laboratory variable HT supply of 5kV with inbuilt safety resistor which I have used for beautiful discharge experiments (pumping down a discharge tube etc). It was the experiments passing electricity through gasses which opened physics up and led to the discoveries of the electron etc. so I think it is very useful in the classroom.

 

[synch]

See if they absorb light at the characteristic wavelengths, it might be a very faint effect though. AFAIK the uranium glass was for fluorescence effects.
The current from a Van de Graff may be too small for good visibility. I think the current through a standard neon sigh tube is eg 10 - 20 mA at several kV, quite lethal !!! Try a car ignition spark coil ?
Begs the question, can I see the glow of a (powered) neon bulb looking through another (unpowered) neon bulb ? Hmm.

 

[tech99]

I have demonstrated absorption lines in the lab using a stick of sodium hydroxide in a Bunsen flame. I arranged lenses to pass an intense beam of tungsten light through the flame and observe with a little spectroscope and camera. Of course, the bright and dark lines are superimposed, so what I found is that if the tungsten light is turned off we see the bright lines, and if the light is gradually increased, it becomes brighter than the bright lines and we see the black absorption lies. It is just a matter of turning up or down the illumination. I also found that above the luminous part of the flame, where it is dark, we can see the absorption lines due to the vapourised sodium ions. I am inclined to think that the Neon would have to be ionised to exhibit absorption.

 

[synch]

Always good to see a demonstration of physics !!