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Author: Subject: CuCl2+CH3OH+DCM=blue flame?
Science Nerd
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[*] posted on 11-7-2019 at 05:34
CuCl2+CH3OH+DCM=blue flame?


Hi,I recently saw you could ignite a solution of copper chloride in methanol and DCM and get blue flame!
Has anyone tried this?
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[*] posted on 11-7-2019 at 06:04


Quote: Originally posted by Science Nerd  
Hi,I recently saw you could ignite a solution of copper chloride in methanol and DCM and get blue flame!
Has anyone tried this?

This is a simple variation to the flame test we are taught in 7th grade science.




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[*] posted on 11-7-2019 at 07:43


I used Copper II Nitrate and that worked as well...you do get a nice blue flame. However, be aware that:

1. You don't much DCM - just a few % ought to be enough
2. You don't need much Cu salt either
3. Burning CH3OH and DCM together makes a nasty smell which, I think, is phosgene. You definitely don't want to do this indoors or upwind of a lot of people. Phosgene is acrid and burns the throat.

Also try Boric Acid for a lovely (and I mean lovely) apple green flame and Lithium Chloride for a pretty decent red. The bonus is that neither of those two require chlorine so no need to use DCM at all. Mg salts are supposed to impart a white colour but I never got that to work very well. And always use methanol, other alcohols will impede the colour production too much.

Cheers


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[*] posted on 11-7-2019 at 08:06


I've never had good luck producing blue. Every other color is easy, but the ones I've tried that are supposed to be blue (various copper salts) are always mostly green. I have not tried adding DCM, though. Is that necessary for blue to work? How?
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[*] posted on 11-7-2019 at 11:46


I lack the theoretical understanding but could the way dcm helps the flame color of copper ions be similar to how chlorine donors are used to impart a brilliant green color in barium containing compositions?
I belive that had to do with a BaCl+ species resonating in the right frequency range,but please correct me if I'm wrong.
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[*] posted on 11-7-2019 at 12:36


Quote: Originally posted by MrHomeScientist  
I've never had good luck producing blue. Every other color is easy, but the ones I've tried that are supposed to be blue (various copper salts) are always mostly green. I have not tried adding DCM, though. Is that necessary for blue to work? How?

The blue emission is from an excited state of CuCl, so you need a flame with Cu and Cl in it.

Possibly not worth getting phosgene poisoning, just for a blue flame.
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[*] posted on 11-7-2019 at 19:45


I'm not doing this (safety reasons and DCM is restricted),just asking.
The book says DCM turns the flame blue by increasing the temperature.
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[*] posted on 11-7-2019 at 20:57


I have never used DCM for this. But it seems reasonable to add a little.

There are a bunch of ways of doing flame tests, and, yes: blues are possible. Although in my experience they seem to often be transient (in the case of copper and zinc) or very faint (Caesium).
If you are interested, I have done a video on this. Capturing the exact colours was problematic since I was filming using a cheap phone. There is a flash of blue at the beginning of the copper sequence and I did not use a very sophisticated set up.

Theory at the start: https://youtu.be/dPVvSv5bnCg
Actual colours obtained: https://youtu.be/dPVvSv5bnCg?t=231
Procedures using OTC reagents: https://youtu.be/dPVvSv5bnCg?t=478




If you are interested, take a look at the latest offering from sum_lab:
A primer on metals and non-metals with at least one novel experiment.
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[*] posted on 11-7-2019 at 23:39


The flame in the book is a really nice blue(like burning natural gas but brighter).
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[*] posted on 12-7-2019 at 00:19


this looks relevant https://en.wikipedia.org/wiki/Beilstein_test
https://www.youtube.com/watch?v=ZKbb-DNJOUc




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[*] posted on 12-7-2019 at 03:30


Yes! The flame is exactly that blue!
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[*] posted on 12-7-2019 at 09:13


I once tried this: I put copper wire in to the natural gas flame until black oxide layer was formed. Than I put wire in to 1+3 HCl for a few seconds. After that I put it back in to the flame. Flame had green colour but after few seconds was colour changed in to blue. After another few seconds was flame orange and finally blue like a normal gas flame.

Green flame - CuCl2

First blue flame - CuCl from decomposition CuCl2

Orange flame - I suppose it was caused by CuCl decomposition in to CuO/Cu2O

Second blue flame - natural gas
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[*] posted on 12-7-2019 at 15:50


Quote: Originally posted by Science Nerd  

The book says DCM turns the flame blue by increasing the temperature.


Get a better book.
If anything, the flame temperature will be lower.

You may find this interesting
https://en.wikipedia.org/wiki/Beilstein_test
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