Sciencemadness Discussion Board

NaNO3 turned black when evaporated at 400F??

RogueRose - 21-10-2016 at 04:54

I had some Ca(NO3)2 that I converted to NaNO3 with Na2CO3. All solutions were filtered until clear and the carbonate had a slight yellow color which carried over to the NaNO3 solution. The CaCO3 was extremely pure and white when finished.

I had some saturated NaNO3 solution that I put in the oven at 400F and it turned brown/black for the most part. The rest of the NaNO3 that had already crystallized is a nice white to off-white cream so IDK why this turned blackish as it all came from the same batch. The oven was set to 400 but may be to 450 which is below any decomp by alot. A glass dish was used with a piece of aluminum lying on the top.

When the blackish material was put in water it turned it a yellow to light brown and dissolved very quickly.

Does anyone know why this my have turned black?

nano3.jpg - 230kB

[Edited on 21-10-2016 by RogueRose]

XeonTheMGPony - 21-10-2016 at 07:35

organic contaminants?

RogueRose - 21-10-2016 at 07:52

I thought I posted the pic. I added it to the original post.


Well that is kind of what I was thinking after my K2CO3 extraction from wood ash and found it turned black with heat. This is all new to me (the organic contamination being noticeable)

I'll take some pics of the off-white NaNO3 to compare. How would I be able to tell if there is organic contamination without heating to this high a temp. Is that possibe?

XeonTheMGPony - 21-10-2016 at 08:36

trace amounts are a pain to try and remove, usually I just remove the contaminated areas and use them for non important things, like making rocket engines or the like

My recent work on some AN I use the contaminated portion to remove an ant hill!

Perhaps peroxide to burn off the organics?

RogueRose - 24-10-2016 at 12:10

I'm wondering what is the best way to clean this. I'm planning on putting it back into solution maybe with a little H2O2 in the water, I don't think that can hurt. Once dissolved filter a few times then evap again, maybe a little differently this time.

Anyone have suggestions on how to clean this?

This is what the "good" stuff looked like when I boiled the solution down. The stuff that got dark was done in the oven at 400F.

What I find curious is when I would boil the water off in a pot on the stove top or on a fire, I would often remove so much water that it was well above the 400F at the bottom of the pot and the mixture was a paste with big bubbles coming up to the top. IDK if it reached decomp temps when it was a paste but it sure didn't turn black.



NaNO3_1.jpg - 32kB NaNO3_2.jpg - 96kB

Maroboduus - 24-10-2016 at 13:04

Was there any corrosion of the Aluminum lid?

vmelkon - 25-10-2016 at 10:04

Perhaps there were organic materials and they got oxidized by the hot NaNO3. I hear that activated charcoal can get rid of such contamination. Just mix and then filter.

I would use an all glass apparatus.
Buy some baking soda and heat it to 150 C to make some clean Na2CO3.

Bert - 26-10-2016 at 05:16

Are you using distilled water, or maybe even rain water for your processes? If you are using well water, do you know what it contains... Here in Northern MN, my untreated well water is hard, acidic and contains TANNINS. Everything made with it, or even a bucket of it just left to stand turns brown on standing a few hours/exposure to sunlight and atmospheric Oxygen.

https://en.m.wikipedia.org/wiki/Tannin

https://www.google.com/url?sa=t&source=web&rct=j&url=https://www.watersystemscouncil.org/download/wellcare_information_sheets/potential_gr oundwater_contaminant_information_sheets/96111501_Tannins.pdf&ved=0ahUKEwikuOOux_jPAhXjxFQKHVDwACEQFggdMAE&usg=AFQjCNEe83AwkVGRiLAnBPwbqvPjdJ6 suA&sig2=eXj1h1E2pAWoZMVMyKcGFg

Any particular reason you are targeting Sodium nitrate rather than Potassium nitrate?

Potassium nitrate recrystalization via lowering temps of a hot, saturated solution is a classic powder maker's procedure. Preindustrial peoples all over the world have done it with basic kitchen implements.

[Edited on 26-10-2016 by Bert]