Author Topic: Geissler tube with a contact problem  (Read 3503 times)

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Offline Gyro

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Re: Geissler tube with a contact problem
« Reply #25 on: January 02, 2018, 10:58:42 am »
There are specific gases that produce a white discharge, eg. Argon. But in this case I suspect that it is imperfectly evacuated air (it needs to be imperfect, otherwise it would be virtually impossible to get a Geissler tube to discharge).

A natural atmospheric combination of mostly Nitrogen (pinkish white to bluish white depending on current density), Oxygen (a bit of Violet/Lavender), CO2 (again, bluish white to pink) and other trace gasses do combine to something whitish at the right pressure. The Automatic White Balance of your camera is probably influencing what we see versus what you see too.

As I mentioned previously, internal pressure was a fairly critical 'trial and error' factor in getting early Geissler tubes to produce a decent light.... and that's a decent light!  :)
« Last Edit: January 02, 2018, 11:02:18 am by Gyro »
Chris

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Offline Cyberdragon

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Re: Geissler tube with a contact problem
« Reply #26 on: January 02, 2018, 05:59:15 pm »
It's probably Krypton.

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Offline Physikfan

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Re: Geissler tube with a contact problem
« Reply #27 on: January 03, 2018, 10:00:46 pm »
In a catalog for physical demonstration devices from 1909 I found one
similar Geissler tube:

 

Offline Gyro

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Re: Geissler tube with a contact problem
« Reply #28 on: January 03, 2018, 10:11:18 pm »
Time to polish up your woodturning skills! The original base would probably have been Ebony, or possibly Mahogany.

Then find a nice safe display case for it.  ;)
Chris

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Offline jpanhalt

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Re: Geissler tube with a contact problem
« Reply #29 on: January 03, 2018, 10:18:29 pm »
Beautiful.  I had the privilege of attending an old university that had unexplored and seemingly forgotten tunnels that had been used for storage beneath the usual basement-level tunnels.  I took home several similar antiques.  Unfortunately, our babysitter/house keeper years later didn't understand the significance of one of the artifacts from the late 19th century, and she broke it.

Don't make that mistake with your find!

John
 

Offline Bashstreet

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Re: Geissler tube with a contact problem
« Reply #30 on: January 03, 2018, 10:32:21 pm »
What a nice tube and the skill to make one... 1909..  :clap:
 

Offline james_s

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Re: Geissler tube with a contact problem
« Reply #31 on: January 04, 2018, 02:02:21 am »
Wow, that's the most amazing Geissler tube I've ever seen.

Looks like you already figured it out but there are various carbon loaded glues and paints that are plenty conductive for this. I just recently found a small jar of carbon paint sold for shielding electric guitars and used it to replace the flaking aquadag on an old CRT, it worked just fine.

Carbon dioxide produces a white discharge and was used in some early gas discharge tubes. IIRC it eventually breaks down into carbon monoxide, I don't know whether it will eventually recombine.
 

Offline Cyberdragon

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Re: Geissler tube with a contact problem
« Reply #32 on: January 04, 2018, 02:52:28 am »
I don't think it's CO2. CO2 and CO are both blueish, where this seems a more pure white. It's probably argon or krypton. But, of course, the color of gas discharges can depend on contamination, voltage and pressure too. And it's possible the camara could be affecting the color. The only way to be sure is to get a spectral reading. You could just use a visual spectrometer (is that what the little plasic tubes with the thin plastic prisms are called?) and compare the pattern to known gasses.
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Offline james_s

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Re: Geissler tube with a contact problem
« Reply #33 on: January 04, 2018, 06:25:20 am »
It's virtually certain that the camera is affecting the color, it's hard to say precisely how though.

I've had an old soft seal helium-neon laser tube turn white, the bore discharge that is, it had completely stopped producing any coherent light long before. I have played with relatively high pressure CO2 in a home made discharge tube and it was bright white. This was at a relatively high pressure compared to most discharge tubes though.
 

Offline Physikfan

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Re: Geissler tube with a contact problem
« Reply #34 on: January 07, 2018, 12:26:26 am »
These are the first, just with reflection grating and camera primitively recorded grating spectra of the Geissler tube:





The second green line of the first spectrum is also in the second spectrum as the middle line and in the third spectrum
included as the leftmost line.

The question is now:
Which gas coresponds to these spectra.

Best regards

Physikfan
 

Offline Cyberdragon

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Re: Geissler tube with a contact problem
« Reply #35 on: January 07, 2018, 01:52:21 am »
Argon?

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Offline Physikfan

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Re: Geissler tube with a contact problem
« Reply #36 on: January 07, 2018, 08:56:02 am »
This is the composite grating spectrum of Spectrum 1 and Spectrum 3.
However, the colors are strongly distorted by the camera's automatic white balance.



The question is still:
Which gas corresponds to this spectrum?

regards

Physikfan
 

Offline Cyberdragon

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Re: Geissler tube with a contact problem
« Reply #37 on: January 07, 2018, 06:08:18 pm »
Is that second band actually yellow or green? If it's green it might be argon as I suggested above, if it's yellow, we'll have to keep looking.
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Offline james_s

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Re: Geissler tube with a contact problem
« Reply #38 on: January 08, 2018, 07:22:40 am »
There may well be more than one gas in there too.
 

Offline Cyberdragon

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Re: Geissler tube with a contact problem
« Reply #39 on: January 08, 2018, 05:31:54 pm »
It would seem to be carbon dioxide. https://www.crtsite.com/page6-4.html

Maybe? Here's carbon monoxide, not sure how it compares to carbon dioxide. Of course it could have decayed as someone suggested.



If it was a mixture, there should be more lines, but of course the OP's crude spectrum may not be picking them up.
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Offline james_s

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Re: Geissler tube with a contact problem
« Reply #40 on: January 08, 2018, 06:03:19 pm »
Hm I had not realized argon had such a broad spectrum. Neon also has quite a few distinct spectral lines in the red-orange region. I've always thought gas discharges are pretty cool.
 

Offline Cyberdragon

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Re: Geissler tube with a contact problem
« Reply #41 on: January 08, 2018, 06:25:06 pm »
Hm I had not realized argon had such a broad spectrum. Neon also has quite a few distinct spectral lines in the red-orange region. I've always thought gas discharges are pretty cool.

Take spectrums with salt. Some elements seem to vary based on the setup used (probably due to measurement sensitivity, like the argon spectrum I posted before looks really dull)

EDIT: The one before actually shows green lines where as this one doesn't
« Last Edit: January 08, 2018, 06:31:42 pm by Cyberdragon »
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Offline Physikfan

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Re: Geissler tube with a contact problem
« Reply #42 on: January 13, 2018, 06:22:46 pm »
I will use such a transmission grating spectrum of a fluorescent lamp (mercury lines) to calibrate the lines of the Geissler tube,
green line 546 nm.
« Last Edit: January 13, 2018, 06:50:10 pm by Physikfan »
 

Offline Samogon

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Re: Geissler tube with a contact problem
« Reply #43 on: January 14, 2018, 01:52:19 pm »
Xenon has white grey-ish white color electric discharge of high voltage
 


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