Public Lab Research note

Carbon Arc

by B.Williams |

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I have been working a small project to allow more energetic reactions than a Propane torch. The concept here is to utilize a Carbon Arc to to achieve this. At present this would be a Lab base device, but could be amended for field work. I am new here at posting information, so hopefully I'll get it correct this time around. Regards Bill

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Carbon Arc 017.JPG 2.48 MB 2012-10-09 23:00:07 +0000

spectrometer spectrometry emission-spectroscopy carbon-arc


I will be uploading a video to my YouTube channel of this device (Carbon Arc) in operation and a bit of explanation relating to it operation later today. Bill

The Video relating to this device is at

I had a welding helmet on at the time of the videoing, my voice is skewed...


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Wow, this is very cool. I've been doing sample prep this morning, eager to try techniques like this for the analysis.

Mind that the original carbon electrodes for carbon arc lamps have a slightly less dense core in order to draw the arc contact there. They are still for sale.

Another configuration is the two carbon electrodes in parallel (some 3mm separation) fixated with gypsum, cast in between. This electrode assembly will have to be absolutely dry of course. The gypsum will be blasted away while this electric candle burns slowly down and the heat of the arc will clear the electrodes, extending their life. This configuration will eliminate the need for adjusting the distance between the electrode points, just their position within the optics (up and down). Ignition has to be made with a third electrode. This kind of electric candle electrode assembly can be easily slotted into its holder. I used a simple 2Kw radiating stove as a ballast resistor in series with the candle, directly attached to 220V mains. You get the classic Star Wars light sabre sound of the AC and everything else on your net segment too like coffee grinders, drills etc.

Drawback of this kind of electric candle is the fairly broad source of light, good enough for lighting purposes like in a lighthouse. But if a point light source is required for more advanced optics, one configuration is a slightly beefier horizontal anode and a vertical cathode from below, so DC fed.

All great fun which requires more than adequate protection for eyes, skin and camera ;-).

Hi Bill - as I'm an admin, i can help embed the youtube video in the body of your post. Interested?

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Sure Jeff.. I will be working up a better video relating to the unit at a later date, but by linking the video will maybe spark interest in the concept. I realize that not everyone will be able to produce a device like this, perhaps in the future plots can look at it and have a device available for the end user. ????

Thanks Bill

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Thanks for the reply... The carbon electrodes I am using are the uncoated plain Jane's as it were and 1/4"(6 mm) diameter. The density to me really at this does not mean much, but it is interesting that the old schooler rods were less dense. My power supply that i have worked up is a DC system... As DC offers up a ay more stable Arc. My main voltage is 120 AC and I control both legs by way of a Relay. The out put from the relay is than rectified to DC thru a FWBR and the voltage is smoothed by a 1700 mF - 450 volt Cap. I also included a Dual heating coil (Ballast) that are switchable so to reduce the resistance by 50% +/- resistance to have a Hi power or Lower power service to the CA. All the circuitry is house in a stand alone enclosure, other than the supply from the mains. I incorporated a Duplex plug to allow the end user to plug in the CA device power supply to reduce the foot print at the work station. I look at the Horizontal electrode with a Ceramic boat on a race drive to put the sample into the arc and decide to go with the vertical format instead. The Cathode rod will be bored to create a pocket as it were for the sample that will be tested. As I referenced in the video the test should only need to ran for 15 seconds to acquire the spectra. As far as reusing the carbons they can be burn to clear them of the old sample and then re-bore to accept the new sample to be tested. I plan on working the housing for the carbon arc fixture tomorrow and will install a filtered view port via # 12 welding lens so the operator can observe the process. and adjust the arc gap if needed. There will be a procedure to setup the CA to center the Arc to the optical axis of the spectrometer and a aliment can be during that time.

Anyway I am rambling again so I'll stop for now

Cheers Bill

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