Sciencemadness Discussion Board - Synthesis of calcium carbide with electric arc

Synthesis of calcium carbide with electric arc

metalresearcher - 24-11-2013 at 09:23

I made CaC2 by arcing lime powder (CaO) and BBQ charcoal and let it react with water. That released acetylene gas with bright flames. So it is rather easy to make carbide when you have a simple electrode welder and carbon rods.

<iframe sandbox width="640" height="360" src="//www.youtube.com/embed/g_sYaBD__YQ?list=UUJArDPDoXa4a1vzvNqvbu1A" frameborder="0" allowfullscreen></iframe>

elementcollector1 - 24-11-2013 at 11:19

For an additional mad science component, check this out: http://mad-science.wonderhowto.com/how-to/turn-microwave-ove...
Warning: High voltage, high temperature.

How good do the carbon rods have to be? I would assume welding grade.

bfesser - 24-11-2013 at 11:47

No references, no analysis. This belongs in Beginnings. I see no evidence that you've produced CaC2. The sparks could just as well be explained by ignition of H2 gas (from the reaction of Ca0 with water) mixed with atmospheric oxygen and the excitation/black-body radiation of various metallic and non-metallic impurities (aerosol). I also don't approve of the assumption that you've achieved 2000 °C.

bismuthate - 24-11-2013 at 11:50

Well it's relativly easy to analyze it. Just mix it with water and test for acetylene.
Try this experiment. It will clearly indicate that you have acetylene.
http://www.youtube.com/watch?v=YtTnYCZJw94

[Edited on 24-11-2013 by bismuthate]

metalresearcher - 24-11-2013 at 11:55

Quote: Originally posted by bismuthate

Well it's relativly easy to analyze it. Just mix it with water and test for acetylene.

View the video from 04:50 and then you see small bright flames when the burner is on the water.
Later I updated this part of the movie with a better C2H2 ignition above the water.
See on
http://www.metallab.net/arcmelt.php?d=#videos
and click on 'Play' (on YT it is not possible to update a video).

bismuthate - 24-11-2013 at 12:00

I don't believe that this is the best way to analyze something because many gases can burn in the same way.

woelen - 24-11-2013 at 12:01

Quote: Originally posted by bfesser

No references, no analysis. This belongs in Beginnings. I see no evidence that you've produced CaC2. The sparks could just as well be explained by ignition of H2 gas (from the reaction of Ca0 with water) mixed with atmospheric oxygen and the excitation/black-body radiation of various metallic and non-metallic impurities (aerosol). I also don't approve of the assumption that you've achieved 2000 °C.

Again, I disagree moving this around. Please stop that endless moving around of threads! This is an attempt at making CaC2 from easy to obtain materials and I see that the process still is far from perfect, but with your remarks and attitude you stifle any enthusiasm right from the start. It is this kind of experiments, which can be a first step to a good working method, by gradual improvements, suggested by other members and supported by further experiments by the OP. Please give constructive comments. How can this process be improved? Do you have any ideas about that? If so, please post them over here! Simply dismissing everything because it has no references and so on is counterproductive and soon will lead to the end of enthusiasm and kills the thread and discussion!

bfesser - 24-11-2013 at 12:05

bismuthate, must you turn everything into an explosive? Why not do a simple redox?

metalresearchethr, the sooty flame is readily apparent in this second video, but not in the first. (It is possible to replace a video; delete and re-upload.)

woelen; I mean no disrespect, but please get off my back. I did provide constructive criticism in pointing out that he should provide a reference for the process (which he claimed to be based on industry), and in proposing an alternate explanation for his (lack of) observations. Also, I don't mean to derail this thread by discussing this here; but there's no problem with moving topics if users are aware of the <img src="./images/xpblue/top_todaysposts.gif" /> <a href="today.php">Today's Posts</a> and <img src="./images/xpblue/top_search.gif" /> <a href="search.php">Search</a> features (if those aren't enough, use <a href="memcp.php?action=favorites">Favorites</a> and <a href="memcp.php?action=subscriptions">subscriptions</a>

. Perhaps posters should put more careful consideration into their posts before just slamming something half-assed up wherever their cursor lands.

[Edited on 25.11.13 by bfesser]

bismuthate - 24-11-2013 at 12:08

Well, it's fun

Jokes aside how do you suggest he test it. That was the best way I know.

woelen - 24-11-2013 at 12:24

I think that indeed the test with the flame was quite good. What else could cause such flames? Of course, it is not a rigid proof, but it is a first step in the right direction.

Commercial CaCl2 produces much more C2H2 per unit weight of material, so the process needs improvement, but it is interesting to see that in principle this can be done in an amateur setting.

bismuthate - 24-11-2013 at 12:29

It was very nice however I only said it was not the best. It truly is actualy a nice test, only it's not definitive.

watson.fawkes - 24-11-2013 at 14:37

Quote: Originally posted by bfesser

Also, I don't mean to derail this thread by discussing this here; but there's no problem with moving topics if users are aware of the <img src="./images/xpblue/top_todaysposts.gif" /> <a href="today.php">Today's Posts</a> and <img src="./images/xpblue/top_search.gif" /> <a href="search.php">Search</a> features (if those aren't enough, use <a href="memcp.php?action=favorites">Favorites</a> and <a href="memcp.php?action=subscriptions">subscriptions</a>

If you didn't mean to derail it, you could have easily move a discussion with another moderator, about a moderation policy, to the Moderator's Lounge, which I take it you are aware of.

Quote: Originally posted by bfesser

Perhaps posters should put more careful consideration into their posts before just slamming something half-assed up wherever their cursor lands.

Yes. Yes, they should.

vulture - 24-11-2013 at 15:06

Making copper acetylide is indeed a good test for acetylene. The question is how to safely dispose of the acetylide.

The formation of CaC2 in electric arc furnaces is so well established that I think we can do without references here.

I'd guess an electric arc easily reaches 2000C, if not more.

metalresearcher - 25-11-2013 at 09:25

Woelen is right. Indeed commercial CaC2 releases much more gas when contacted with water. I think lots of CaO vaporizes and lots of unreacted CaO + carbon mixes with the CaC2. Moreover, silicates from the crucible (hole in a concrete brick) can also contaminate the melt. Overheating can also
be an issue as I read in the literature, then it decomposes. The arc itself reaches easily over 3000 C but very locally. As I can see so far, the CaC2 is formed in the liquid state.

[Edited on 2013-11-25 by metalresearcher]

bfesser - 25-11-2013 at 11:19

Quote: Originally posted by bismuthate

Jokes aside how do you suggest he test it. That was the best way I know.

You mean only? You might try studying basic General and Organic Chemistry sometime, in addition to Energetic Materials; you might just find something else which peaks your interest—if not, at least you'll learn something. Studying one area of interest in great detail is admirable, but it couldn't hurt to "expand your horizons."

<a href="http://en.wikipedia.org/wiki/Alkyne#Reactions" target="_blank">Alkyne: Reactions</a> <img src="../scipics/_wiki.png" />

Facile tests for ethyne (unsaturation) which don't involve preparing explosives:<ul><li>decolorization of very dilute KMnO4(aq)</li><li>decolorization of <a href="http://en.wikipedia.org/wiki/Bromine_water" target="_blank">bromine water</a> <img src="../scipics/_wiki.png" /></li><li>spontaneous reaction <a href="https://www.flinnsci.com/media/620548/91234.pdf‎" target="_blank">with chlorine</a> <img src="../scipics/_pdf.png" /></li></ul> Attachment: ethyne.doc (39kB)
This file has been downloaded 2330 times

[Edited on 25.11.13 by bfesser]

vulture - 25-11-2013 at 14:31

Given the possible hydrogen content I would caution against the chlorine test.

metalresearcher - 30-11-2013 at 10:46

Well here I did a test of the chunks into water and got a nice acetylene flame !

<iframe sandbox width="640" height="360" src="//www.youtube.com/embed/zL5ZNIzKF30" frameborder="0" allowfullscreen></iframe>

bfesser - 30-11-2013 at 10:57

Very nice. Although it's generally considered poor practice (unsafe) to set fire to a jet on a container of flammable gas like that before you're 100% certain that oxygen has been displaced from within. With a plastic bottle, however, the risk is greatly reduced; but please be careful with your experiments. Do you plan to continue work toward improving this process?

[Returned to Technochemistry. Sorry, I shouldn't have moved it to begin with.]

[Edited on 30.11.13 by bfesser]

metalresearcher - 30-11-2013 at 13:56

@bfesser: Yes, I try to improve the process.
The lime I used turned out to be slaked lime Ca(OH)2. That did work but now I heated the Ca(OH)2 to 600 C to convert it to CaO and when I use that the yield of CaC2 is better. Now I fill a container with crushed charcoal, put two carbon rods into it 1-2cm apart, put some CaO powder on it and let it slowly start and run for 1-2 minutes. The charcoal itself acts al electrodes and resistance heating.
Then I let it cool and the harder chunks within are (impure) CaC2 which fizzle strongly with water.

BobD1001 - 30-11-2013 at 14:02

Great work! Very cool to see someone successfully synthesize calcium carbide in the home lab setting!

IrC - 4-4-2014 at 13:04

While chemistry is not my area of study I have learned enough to wonder about the possibility of CaCN also being a byproduct since in an amateur home setting likely this experiment will be exposed to N2 in the air unless this was conducted in a controlled atmosphere. I bring it up since I believe it should be considered by beginners in the field doing this at home. The last thing one should be doing is cavalierly handling products which may contain cyanide they are completely unaware of. Or am I just being overly paranoid here?

smaerd - 5-4-2014 at 06:30

Very cool as always MetalResearcher.

Out of curiosity how are you moving the electrodes safely?

NedsHead - 10-7-2015 at 04:36

I dusted off my welder, bought a bag of lime and gave this synthesis a go today, the first few attempts didn't yield much calcium carbide, I think I was decomposing the CaC2 through overheating.

Once I got my temperature somewhat under control I had great success, the chunks of calcium carbide synthesized reacted strongly when dropped into a glass of water, so strong that once lit the flame was self sustaining. An Impressive success!!

ave369 - 12-7-2015 at 23:38

Is this method suitable for synthesis of other carbides, such as Al4C3 and Mg2C3?

NedsHead - 15-7-2015 at 21:39

Below are some pics of today's results, still pretty good but I haven't been able to reproduce the excellent results I had last week. That'll teach me for not taking notes

[Edited on 16-7-2015 by NedsHead]

NedsHead - 18-7-2015 at 01:26

https://youtu.be/IjQ_q8hg6ic
Here's a video of today's freshly made Calcium Carbide reacting with water, the issues I was having have been resolved.

battoussai114 - 18-7-2015 at 09:35

That's pretty interesting! I have a few ideas where acetylene would be useful and I've been wanting to make something more interesting than melting nails with my arc furnace.

NedsHead - 18-7-2015 at 15:56

Give it a go battoussai114, CaC2 is near impossible to come by around me and there's no way I'm paying chemical suppliers prices for high purity. I found it very rewarding to be able to make this at home and it produces enough acetylene for my needs

franklyn - 24-7-2015 at 04:20

http://www.sciencemadness.org/talk/viewthread.php?tid=17165#...

http://www.sciencemadness.org/talk/viewthread.php?tid=13144#...

.