I was attempting to microwave-heat a concentrated NaOH solution stored in a small 25 ml TPX beaker when I got a pretty large number of orange sparks
and occasionally transient orange flames, very characteristic of sodium.
It’s like microwave heating was forming small beads of sodium which were set on fire. That’s not a very satisfactory explanation. Does anyone
possibly know what's going on here?
Cf. attached video
Attachment: IMG_0181.m4v (4.6MB) This file has been downloaded 596 times
[Edited on 11-6-2019 by Keras]Sulaiman - 11-6-2019 at 04:50
conductive loops convertng microwave to heat energy, exciting the sodium ions (!)
I guess a similar result with NaCl ?
I guess not metalic sodium production.Ubya - 11-6-2019 at 04:57
if this happened after the solution started boiling maybe droplets formed by the boiling absorbed enough microwaves to ionize, the yellow is the
characteristic color of sodiumRogueRose - 11-6-2019 at 05:45
I get similar results when boiling down KCl solutions, I get small sparks/flames on the surface when it is near peak saturation and boiling. Keras - 11-6-2019 at 07:00
I’ll try with NaCl and see if I get the same thing.
I get similar results when boiling down KCl solutions, I get small sparks/flames on the surface when it is near peak saturation and boiling.
Are your sparks/flames red, which would indicate K+ ions?
[Edited on 11-6-2019 by Keras]Keras - 11-6-2019 at 09:39
I confirm a saturated NaCl solution produces the same yellow sparks (no flame, though)
I think this happens, as someone suggested, when small droplets that adhere on the walls of the beaker boil and evaporate, and the salt crystallises
out. It may happen when crystals form, because I also see sparks under water.
I tried with dry sodium chloride, got nothing. Stopped after a short while, I didn’t want to fry the magnetron.
[Edited on 11-6-2019 by Keras]RogueRose - 11-6-2019 at 10:05
I get similar results when boiling down KCl solutions, I get small sparks/flames on the surface when it is near peak saturation and boiling.
Are your sparks/flames red, which would indicate K+ ions?
[Edited on 11-6-2019 by Keras]
The are small enough to be difficult to tell what color they are, they look more like sparks and I would say they are more yellow than purple/red. I
don't know how pure the KCl was, it might have been 95/5% KCl/NaCl. happyfooddance - 11-6-2019 at 10:33
This happens in general with ionic solutions, especially concentrated ones. It's the reason I don't heat salt solutions in the microwave (ruined too
many microwaves, think I'm on number 3 or 4).
I would also be very careful because the container can get extremely hot right at the surface, forming a ring. Plastic may melt and the contents will
start to pour out.
I once was dissolving a few hundred grams of KNO3 in water in a mason jar in the microwave, which used to be my preferred method for this scale, when
the sparks got out of hand. I turned it off, but the jar split perfectly in half about the liquid interface. So I don't do that anymore...mayko - 11-6-2019 at 12:59
