Junk_Enginerd
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Nitric acid bottles growing exterior crystals?
I have a bottle of nitric acid that's started growing crystals after a year or so. It's mostly around the cap. This has me mildly concerned about what
it might be. This is most prevalent with my home made RFNA, my commercial 68% nitric acid is showing much less of this. What are these crystals? They
are translucent, long, thin and very fragile.
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Bedlasky
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I don't know what the crystals are, but fuming nitric acid attack plastics. Even plastic caps from duran bottles are significantly damaged after a
month. Only ground glass flasks and glass ampules are suitable for long term storage.
[Edited on 21-1-2024 by Bedlasky]
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Sir_Gawain
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Is it stored near anything volatile that could react with it, like ammonia? Perhaps it’s reacting in gas phase and depositing solids.
“Alchemy is trying to turn things yellow; chemistry is trying to avoid things turning yellow.” -Tom deP.
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woelen
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It most likely is ammonium nitrate, or amine nitrates. If you have animals (pets!) around, then this is even more likely, due to presence of ammonia
or amines from these animals.
I would not worry about these crystals, no risk of explosion. Just wipe them off with a moist towel and rinse the towel with some water.
It, however, is an indication, that the acid is not stored well for long term storage. Fuming nitric acid is amazingly hard to keep around for a long
time. I would suggest to use it up quickly. It also is not safe to ampoule it, because the acid may decompose, with one of the decomposition products
being oxygen. That may lead to pressure buildup and explosion of the ampoule.
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Junk_Enginerd
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Ahhh yeah of course. I was wondering what on earth the supposed NO2 could be forming salts with just out of thin air, but ammonia seems reasonable.
Googling ammonium nitrate crystals supports this as well, it looks very similar. And yeah, I have ammonia bottles in the same space, and a kitty
litter box nearby too lol. Mystery solved!
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Raid
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Any pictures of the crystals?
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Tsjerk
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I just noticed my bottle of 96% sulfuric acid is 'sweating'. The bottle is in a cupboard in a unheated shed here in the Netherlands. I didn't touch it
in two years.
I expect the bottle to have heated 20+ degrees at least 10 times now. The bottle is 2.5 liters, with at least 1.5 liters head space. The 'sweat' is
acidic, but only slightly. I expect it to be a couple percent sulfuric acid, the acid was released during hot days and will never evaporate,
attracting a lot of water while being there.
[Edited on 3-2-2024 by Tsjerk]
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4-Stroke
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I know that this isn't helping anyone solve this, but I have the same problem! Except that I don't have ammonia or anything else I think can react (no
pets either  ) anywhere near the nitric acid. The battle is made out of glass, but
the cap is metal. I put Teflon tape over the threads, and now there are crystals. Any idea what can be causing the crystals in this situation?
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Sir_Gawain
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It’s probably reacting with the metal cap. Do you know what metal it is?
How did you make your nitric acid? Is there any way it was contaminated with sodium sulfate or some other salt?
“Alchemy is trying to turn things yellow; chemistry is trying to avoid things turning yellow.” -Tom deP.
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4-Stroke
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Yeah it does seem to be reacting with the cap (or at least the paint on it). I'm not exactly sure what the metal is, but it is non-magnetic, so it
isn't iron. Aluminum, perhaps? Here, I'll post a picture so you can see what I'm talking about.
There is quite a bit of the crystals. Also that moisture is OUTSIDE of the bottle. Though it isn't nitric acid because when I smudge it on my fingers,
I don't get that nitric acid burn. But it is still caustic. As for my nitric acid, I made it out of sulfuric acid and somewhat pure sodium nitrate. I
didn't get any foaming or bubbling over, but I am sure that it is not very pure or very contaminated either.
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Sir_Gawain
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That’s definitely the problem. You need to get a cap made out of something else—preferably Teflon.
“Alchemy is trying to turn things yellow; chemistry is trying to avoid things turning yellow.” -Tom deP.
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4-Stroke
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If only I could afford one... But what can the crystals be? I know that aluminum can react with nitric acid someway, but surely it can't just turn
into translucent crystals, can it?
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chornedsnorkack
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Quote: Originally posted by 4-Stroke  | | If only I could afford one... But what can the crystals be? I know that aluminum can react with nitric acid someway, but surely it can't just turn
into translucent crystals, can it? |
https://www.sciencemadness.org/smwiki/index.php/File:Alumini...
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4-Stroke
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Ah yes... aluminum nitrate. I don't know how it didn't cross my mind earlier, but thanks! I guess that now the issue is solved for me too 
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