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Author: Subject: nitric acid storage
Arthur Dent
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[*] posted on 25-12-2010 at 07:54
nitric acid storage


I know how hard to get HNO3 is right now so I'm very happy to still have that big 3-liter bottle (3/4 full) of 42 BE nitric acid that I acquired way way back (over 25 years ago).

At that time, that bottle I bought from Anachemia was labeled by weight (7 pounds).

All these years after, the acid is still crystal clear, but i've recently noticed a ring of brown dust aound the bottle. Fearing that it was somehow getting old, I cleaned-up the surface of the bottle, and discovered that the underside of my steel shelf had slowly oxidised right through the white paint and was "shedding" some Fe2O3 right on top of the bottle. Nitric acid is indeed a strong oxidizer!!!

Being tight for space and this spot being the only place where I can store the acid, I decided to try to stop the corrosion by smearing the underside of the shelf with a thin film of automotive black grease.

But I may eventually switch to a plastic shelving unit.

So my question is, does HNO3 have a "limited shelf life"? And as mentioned, I keep my bottle in a plastic container at the bottom of my shelf. Are there other precaution I should use to keep my precious HNO3 safely, for my own health and the sake of my tools, since the shelf is in my tool storage area inside my home.

I have had no oxidation on my tools and aside from the limited oxidized area on my shelf, nothing else seems affected.

Robert
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Random
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[*] posted on 25-12-2010 at 08:56


Are there other precaution I should use to keep my precious HNO3 safely, for my own health and the sake of my tools, since the shelf is in my tool storage area inside my home.

Answer to this question:

Be careful every time you use it because of NO and NO2 gasses, which are especially created when it's dissolving copper. Those gasses could cause pulmonary edema.
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bfesser
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[*] posted on 25-12-2010 at 10:43


Perhaps a Parafilm or paraffin wax seal around the cap/neck would help?
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Arthur Dent
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[*] posted on 25-12-2010 at 12:45


@ Random: Totally agree. Any and all experiments with the HNO3 are done outdoors, even transferring the acid from the bottle to a vessel.

@ bfesser: An interesting idea, I have a few jars of chems that used this technique of a "wax ring" to protect hygroscopic compounds from sucking in the atmosphere's moisture. Don't know however if it works the reverse way, preventing HNO3 vapors from escaping from the bottle.

Since HCl is less complex to obtain, and evolves much more highly oxidizing gas (bad for tools), I keep my plastic HCl bottle outside in open air. Even at -30 C, there's no risk that it freezes or bursts.

But getting back to the HNO3, if kept at room temperature in a dry place, I imagine it should last an eternity, right?

Robert
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[*] posted on 25-12-2010 at 13:43


i have also an old bottle of HNO3 " from my supervisor" but what is the color of yours ? mine is yellow " deep " .
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mr.crow
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[*] posted on 25-12-2010 at 14:10


68% nitric acid is an azeotrope that boils at 120 degrees, so it is less volatile than water. I'm not sure about stability, hopefully it doesn't turn too yellow.

I would be more worried about conc HCl, a fuming evil liquid.




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[*] posted on 25-12-2010 at 14:11


Teflon plumbing tape around the stopper. Anything else, including wax, will be attacked.



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[*] posted on 25-12-2010 at 16:40


One other option would be to replace the cap. The cap liner could be getting eaten away.
I know that the new bottles that Anachemia use have a 38/439 or a 38/430 threading.
There are Teflon lined versions of both caps made. Not sure about the older ones.
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Lambda-Eyde
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[*] posted on 25-12-2010 at 17:05


Quote: Originally posted by Arthur Dent  

But getting back to the HNO3, if kept at room temperature in a dry place, I imagine it should last an eternity, right?


Keep it in an amber bottle in a dark place and it will last forever. Once I encountered a 5 L bottle of 65% HNO3 deep in a cupboard at a factory nearby, presumably 20-30 years old. It was still crystal clear, but some bits of debree were floating in it because the blue GL45 PP cap had swollen and started decomposing...
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Arthur Dent
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[*] posted on 26-12-2010 at 10:26


@TheOrbit : As you can see, the acid is still water-clear after 25 years+, but you can see the damage to my shelf just above the bottle, getting rusty and shedding fine rust particles. The sulfuric acid on the other hand, hasn't provoked any oxidation was bought on the same day.



@vulture : Teflon tape? Yeah, that might be the trick!!! Thanks! Would I put the teflon tape on the glass threads or simply wrap it over and around the cap?

@undead_alchemist : The cap seems to be mostly intact and in perfect condition, although the liner seems to be a bit darkened. I don't know if caps like that are still available.

Robert
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