Sciencemadness Discussion Board

Storage of Fuming Nitric acid

Saber - 12-6-2009 at 13:31

Every time I required Fuming nitric acid in the past, I would make it in situ by distill a mix of NaNO3/H2SO4. The only reason I did this is I don’t have any bottle strong enough to withstand the fuming acid. As many of you know, when you need it on a day to day basis this gets very tedious! What I hate the most about this is it develops quite some NO2, which, although I have a perfectly good hood, I still don’t like working with.
As a result of this I have decided I would like to make a large batch of the acid and store it. I have a number of questions on this however;
Firstly the acid decomposes into O2, does this mean there will be a significant pressure buildup, every time I open/close the bottle?
Secondly, is it better to store WFNA or RFNA? My guess is WFNA as it is less oxidizing but this is a mere guess.
Finally has anybody else bought fuming nitric acid from a supplier? If so, what type of bottles does it come in? and what is the screw cap like? Eg, glass?
I have read storing any type of <80 nitric acid in aluminum is fine. Is this true?

Jor - 12-6-2009 at 13:42

I have heard WFNA decomposes much more easiliy, and is a greater storage hazard.

You have 2 choices:

-PTFE/Teflon bottles
-Thick glass bottles with PTFE liners (preferabely DURAN).

Member Fleaker has recommended:

I have bottles with release vents, wich release overpressure. I use this to transport my waste safely, as I give it to another chemist who throwns it in their waste container in their lab. Try to find one of these.

Why is NO2 a problem in a hood? Even a simple homemade hood will simply get rid of nitrous fumes easiliy, and these are not really dangerous anymore with a fume hood.

hissingnoise - 12-6-2009 at 13:52

HNO3 stored in Al containers has had an inhibitor (HF) added to protect the Al.
Merck safebreak bottles are good as the screw-caps (PE) have a teflon insert which effects an airtight seal when tightened. . .
Stored in a cool, dark place, HNO3 decomposition is slow and pressure build-up minimal.

DJF90 - 12-6-2009 at 17:15

hissingnoise: Very concentrated nitric acid will passivate aluminium and hence will not require an inhibitor. If I were to store it personally, it would be in an amber bottle with a PTFE lined cap and kept in a cool dry place, as many chemicals should generally be stored.

Fleaker - 12-6-2009 at 18:19

Saber, get one of those FEP bottles if you want to store it. You should store RFNA rather than WFNA, in the dark. It will store for years.

Also, those FEP bottles can be used to store all the oleum you make with your contact process (which I still want to see).

hissingnoise - 13-6-2009 at 03:59

Quote: Originally posted by DJF90  
Very concentrated nitric acid will passivate aluminium and hence will not require an inhibitor.

In commercial practise IWFNA/IRFNA is preferred---the fluoride may form a tougher passification layer than the oxide. . .
I'm guessing, though!

panziandi - 13-6-2009 at 04:32

If I were you I would store RFNA and store it in an amber glass bottle with a teflon lined PE lid. Store that bottle in the dark and cool, preferably inside a secondary container.

RFNA has a fair amount of dissolved NOx which displaces the equilibrium of nitric acid breakdown to the left. WFNA can be readily made from RFNA, when required, by passing a brisk current of warm, dry air through the acid to remove the dissolved NOx.

Indeed, commercially HF is added to FNAs to passivate the metal containers with a F layer. Concentrated nitric acid does indeed passivate some metals, but HF passivation is better.

benzylchloride1 - 13-6-2009 at 21:52

I store my white fuming nitric acid in a pyrex glass stoppered nitric acid bottle. The stopper seals well and I have not had a problem. I store less then 100 mL at a time.

Picric-A - 14-6-2009 at 07:28

Why dont you just make it as and when needed?
that way you dont have to worry about overpressure/corrosion ect...
If not use an pure aluminium bottle and gas the FNA with some anhydrous HF so its around 1%.

Lambda-Eyde - 14-6-2009 at 07:35

>96 % white fuming nitric acid is commonly stored in amber bottles with fluoropolymer lined caps, even in schools.
As long as it is stored like that and in a cool place, I don't think there would be any problems.
If you want to be really sure, you could probably relieve the pressure once a week.

Picric-A - 14-6-2009 at 07:38

Relieveing pressure would release a cloud of toxic/corrosive fumes, along with weakening the acid, and most of all be a pain to do it weekly!
just make it as and when needed!

DJF90 - 14-6-2009 at 08:29

Do you not read the thread... He said he was tired of making it when needed! And it would be less of a pain to release pressure weekly than to have to make it every day. Just when I thought we got rid of an idiot you turn up again. Great.

[Edited on 14-6-2009 by DJF90]

Ozonelabs - 14-6-2009 at 08:52

We keep ours stored in the original BDH container-

That is kept in a large HDPE screw top container which has Sodium Carbonate at the bottom.

hissingnoise - 14-6-2009 at 09:04

Pressure release isn't necessary at normal temperatures---decomposition of HNO3 produces NO2 + H2O and NO2 promptly dissolves. . .
Below 0*C decomposition is practically Zero.

DJF90 - 14-6-2009 at 09:05

That bottle looks strangely blue... Is that how it actually is?

UnintentionalChaos - 14-6-2009 at 09:17

Quote: Originally posted by hissingnoise  
Pressure release isn't necessary at normal temperatures---decomposition of HNO3 produces NO2 + H2O and NO2 promptly dissolves. . .
Below 0*C decomposition is practically Zero.

You have an unbalanced equation there.

4HNO3 --> 4NO2 + 2H2O + O2

It's the oxygen gas that pressurizes the container, not the NO2.

Ozonelabs - 14-6-2009 at 09:17

Yes, it is actually that blue.

The bottle is actually a bottle in a bottle. The one that is in direct contact with the acid is opaque and blue, there is a solution of some description between the two layers of plastic and the outer layer is clear plastic.

hissingnoise - 14-6-2009 at 09:44

Quote: Originally posted by UnintentionalChaos  

You have an unbalanced equation there.

Ooops! Yes, I must be getting Oldtimer's---but O2 too dissolves to a large extent.
The pressure generated certainly isn't enough to be a problem at normal temps. . .

Saber - 14-6-2009 at 11:40

Thanks for all your replys,
@ Picric-A - If you hadnt picked up fag ends and read the rest the rest of the thread you will of read me saying how i do not want to keep generating it in situe, so yes i want to store some.
@Ozone- Nice bottle you have there! whats the cap made of? just thick PTFE or glass?

I am searching for a place to buy PTFE bottles, as they would be extremly usefull, not only for fuming nitric buy for HF also.
until then i may just store it in a quickfit flask as benzylchloride1 mentioned.

panziandi - 14-6-2009 at 13:32

Saber - The lid on that safe break bottle is likely PE with a PTFE liner.

You can pick up cheap glass bottles with ground glass stoppers on eBay (sometimes with Nitric Acid engraved on them!) if you check lab supplies, failing that try searching for "pharmacy bottles" or "poison bottles" may get something useful that way?

As to PTFE bottles... these are VERY expensive! IIRC a 15mL one would have set me back about £12! Instead, opt for a HPDE bottle for HF with a PTFE lined PE lid. These are quite suitable for HF solutions including 48% stuff. I personally wouldn't store FNA in PTFE bottles, they are bad to grip for starters, but also its just overkill IMHO.

How much do you think you will make in one go to store?

Jor - 14-6-2009 at 14:06

Saber, are you seriously considering having HF in your home lab?
This stuff is very dangerous! I wish i could have it, as it is so interesting, but the hazards are too great!

Ozonelabs - 14-6-2009 at 14:10

Saber- I will inspect the bottle the next time I'm at the lab and let you know.

Jor- Following our P.M.'s it is possible to keep and use HF safely in a 'home' lab. We do- and there have been no incidents.

Jor - 14-6-2009 at 14:49

Quote: Originally posted by Ozonelabs  
Saber- I will inspect the bottle the next time I'm at the lab and let you know.

Jor- Following our P.M.'s it is possible to keep and use HF safely in a 'home' lab. We do- and there have been no incidents.

Yes Ozonelab, you are indeed an exception. You work with fume hood, thick gloves, lab coat, shield, Ca-gluconate gel, and most importantly, with 2 persons! Working alone with HF is not so smart.

I can imagina that only very few people can follow these critical precautions on working with HF.

Formatik - 14-6-2009 at 15:29

If you store the fuming HNO3 in a glass bottle with a glass stopper, then you shouldn't have to worry about overpressure accumulation. I think in this case if you kept the stopper loose that too much pressure inside would push the stopper up, before the bottle would reach the point of bursting.

I haven't tested it out with large amounts, but had a few bottles of a testing acid for goldsmithing in brown glass small bottles and glass stopper, judging from the red color of the acid and fumes seemed like RFNA. Those were stored for years in the dark and never burst.

Btw, tin has very good resistance (much better than aluminium, even at elevated temperature) according to this paper: Gold and tantalum too, but who cares about those.

hissingnoise - 15-6-2009 at 04:23

DSC_0008 copy.jpg - 65kB
This is the Merck Sb bottle---this acid has been stored at temps close to 30*C and no outrush is noticed on opening.
Once in the bottle with the cap tightened you can forget it till it's needed. . .

woelen - 15-6-2009 at 04:37

This only is true for red fuming nitric acid. I have made red fuming nitric acid and indeed there is no strong pressure buildup. I also had white (actually pale yellow) fuming nitric acid and that did build up pressure and the color of this material slowly intensified!

Apparently, the presence of large amounts of NO2 prevents decomposition of the acid, but pure HNO3 (without NO2) does decompose slowly. I "discarded" the white fuming nitric acid, I did not feel comfortable with this stuff around. I simply dumped it in the bottle of red funing nitric acid and now I don't have any storage issues anymore. I now have a total of 50 ml of fuming acid, made from the red and the white acid. Up to now I hardly found any use for the fuming nitric acids, I just made them for the fun of making them and showing that I indeed can make them.

Jor - 15-6-2009 at 08:55

You can use fuming nitric acid to make iodic acid, by refluxing it over iodine. However, for every mole of iodic acid formed, 5 mols of NO2 form, so this is a LOT of NO2.
I would prefer making iodic acid from chloric acid and iodine, the chloric acid is readily prepared from potassium chlorate and tartraric acid, as K-tartrate is very insoluble. There is a write-up on this on versuchschemie.

Saber - 15-6-2009 at 09:41

I was thinking of making around 250ml of FNA at a time to store.
Does RFNA have different nitrating properties than normal WFNA? Its a rather stupid question however i jsut want to be sure becuase the presence of large quantites of NO2 may act as a very good oxidiser.
As to the HF, dont worry, i have no intention of making/using any, it was just a theory of what i could use the PTFE bottles for. Anyway, ive heard HDPE is good for storing >40% HF.

Rather off topic however i thought this looked do-able:
A process to make fuming HNO3 from HCl(g) (from NaCl/NaHSO4) and NO2 (decompostiton of Calcium nitrate fertilizer, )

[Edited on 15-6-2009 by Saber]

Fleaker - 17-6-2009 at 12:51

Good grief! What is wrong with storing it in a FEP bottle? They're practically made for nitric acid! Here's the bloody ebay item number:

Even with shipping to England, they're still ridiculously cheap in comparison to what VWR or Fisher sells them for.

If no one has bought any yet, shame on you!! I run my mouth about how great those bottles are all the time, well, because they are great: great for HF, great for HNO3, great for TFA, great for oleums, great for perchloric, great for HI, great for every acid.

As for the RFNA, no it doesn't build up significant pressure even upon months of storing at ambient temperatures while in the dark.

Saber - 18-6-2009 at 06:35

Someones a fan of FEP bottles i see ;)
I will try get one of those bottles and try em out. I admit it would be usefull storing Oleum...

Fleaker - 19-6-2009 at 12:39

Fan? If those bottles were a woman... (zero maintenance) :P

Please though, I really want to see your Contact process!!!! I have performed the experiment 3 times at the bench scale and it definitely works; I would love to see how you attempted it.

Saber - 20-6-2009 at 13:55

Wait till the 2nd of August (my birthday- im getting a digi cam)!!!
Which experiment did you perform? The oxidation of SO2 using V2O5?

Fleaker - 21-6-2009 at 08:56

I did the vanadium (V) oxide-catalyzed oxidation of SO2 and obtained interesting and encouraging results. I lost interest and moved onto another project quite some time ago but I really liked the oleum project. It was just that I had no need for any oleums or SO3.

That said, please do post it up. I'd like to see your Contact process with which you make useful quantities of oleum.