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Author: Subject: Elecric arc colors of CaO + charcoal ?
metalresearcher
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[*] posted on 2-11-2015 at 09:52
Elecric arc colors of CaO + charcoal ?


Last weekend I made CaC2 with my DC welder using 120 amps by arcing crushed charcoal with CaO powder. The enclosure is YTONG cell concrete as I don't have proper MgO refractory.

Most of the time the color is bright pink / magenta (03:30 in video below) but sometimes green (2:05).

Pink I can understand (calcium) but green ? No borax, barium, zinc or copper salts (which color flames green) were in the furnace. And the copper tubes which hold the carbon rods were not immersed inside the furnace, otherwise it would melt. Close to the arc the temperature is over 2000 C.

Here a clip of the arc furnace inside my fumehood.

http://www.metallab.net/jwplayer/video.php?f=/clips/CaC2%20m...
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[*] posted on 2-11-2015 at 13:13


Was it a virgin furnace, or is it possible that residue from previous experiments were present?



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metalresearcher
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[*] posted on 2-11-2015 at 13:57


I have done previous experiments, but with the same chemicals, i.e. CaO and charcoal.
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chloric1
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[*] posted on 2-11-2015 at 15:35
Overall a success


This has been the most successful home brew carbide video I have seen yet. I bet you are so excited. You should next try calcium phosphide.

FYI. I have an Ebook copy of Moissons "The Electric Furnace". I find it is interesting that carbon can displace phosphide and sulfide with prolonged heating. It's because calcium carbide is more thermodynamically stable. So you could use gypsum in a pinch. Would take quite a awhile though. Maybe need more current?:o




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[*] posted on 2-11-2015 at 18:01


Hi metalresearcher,

your success making Calcium Carbide was the reason I gave it a go myself and I've noted a few things: the green glow is necessary and appears to indicates there are enough amps for the reaction, (I'm curious why its green as well) but too many amps will destroy the product so adjust the amps until the green glow first appears, for my DC welder it's 110A.

Next, keep the reaction as short as possible, 4 minutes is far too long and will destroy the end product, try 60-90 seconds, draw the arc around the crucible to react as much of the carbon and CaO as possible (I use Calcium Hydroxide), hold the electrode in one spot until the carbon and caO sublimate and then move the arc to a new spot and react.

This method yields me some very good calcium carbide https://youtu.be/IjQ_q8hg6ic

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metalresearcher
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[*] posted on 3-11-2015 at 10:30


BTW, will tungsten rod electrodes not work better (i.e. less wear) ? They are available for a reasonable price on ebay.
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[*] posted on 3-11-2015 at 12:18


What was the source of the graphite electrodes?
If you used gouging rods (gutselectroden in Dutch), they are typically plated with copper when you buy them. If you used those: did you strip their copper layer off before use, and (if so), how?




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m1tanker78
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[*] posted on 3-11-2015 at 13:01


The green emission is probably copper plating bath residue trapped within the graphite. Even if you peel the copper sheathing off the electrodes without tearing it, there will be some copper salt(s) adhered beneath the surface.

Quote: Originally posted by metalresearcher  
BTW, will tungsten rod electrodes not work better (i.e. less wear) ? They are available for a reasonable price on ebay.


Tungsten electrodes will work only in an inert atmosphere and at relatively low current with some form of heat sinking (or sweeping argon over them). Carbon is hard to beat in an arc furnace. Unprotected/overheated tungsten will oxidize very quickly and aside from burning up, will contaminate your product.

A robust resistive electric furnace can be made using some thin gouging rods and some high temp masonry. Have you considered making such a furnace? Seems like your cement insulates fairly well. Might be worth a shot.




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metalresearcher
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[*] posted on 4-11-2015 at 09:05


Quote: Originally posted by phlogiston  
What was the source of the graphite electrodes?
If you used gouging rods (gutselectroden in Dutch), they are typically plated with copper when you buy them. If you used those: did you strip their copper layer off before use, and (if so), how?

These rods are not copper plated, just pure graphite. I got them from a Chinese ebay supplier.


[Edited on 2015-11-4 by metalresearcher]
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