Sciencemadness Discussion Board - Fuming nitric acid storage

Fuming nitric acid storage

sbreheny - 12-9-2015 at 17:41

Hi all,

About a month ago I made some fuming nitric acid by reaction of concentrated sulfuric acid with sodium nitrate, followed by distillation. It worked very well - based on careful density measurement it looks like I got 94% nitric acid. It sure fumes a lot!

I made about 100mL. My first attempt at storage was in an amber glass bottle with one of those green-colored Qorpak PTFE-lined caps. It worked fairly well BUT every time I opened the bottle, the vapors would deposit a little bit of acid on the threads of the cap. This eventually weakened the cap and it cracked. I replaced the cap, but I found that the vapor was even able to get around the liner and attack the non-coated side of the liner and cap from the top. I think this was also related to deformation of the liner during opening and closing.

Finally, I got a really expensive Nalgene FEP bottle with Tefzel cap. This has stood up well so far, but I notice something puzzling. The outside surface of the bottle develops a thin layer of liquid droplets, just like condensation, but this liquid is acidic and it has a slight strange smell - not acrid like nitric acid but some kind of amine-like smell. This does not happen to glass or LDPE bottles in the vicinity so I don't think it is condensation of water or any other chemical in he area.

Do you think that the nitric acid is permeating the bottle? After several weeks of storage, the total mass has not changed (to within one gram).

Sean

annaandherdad - 12-9-2015 at 18:11

I'm sorry to hear this. I got the same kind of bottle with the same kind of cap, and was planning to use it for RFNA. I wonder if it would be all right if you rinsed and dried the cap after after use.

KesterDraconis - 12-9-2015 at 20:31

I don't even store things like WFNA or 30% hydrogen peroxide for long periods of time after I make them. If I need them, then I make them the day before or a couple days before, and just keep them in a beaker with a watch glass or something on top to keep stuff from falling in and contaminating them.

The reason for this being that I had a small bottle of 30% H2O2 explode when the gas inside built up and blew off the top. I know that this can be fixed just by opening the containers now and then to release and pressure, but I also know I am too lazy or forgetful to do so. (hence why the hydrogen peroxide bottle blew up in the first place)

Besides, its not really that hard to prepare chemicals for an experiment. For WFNA you just need to set up your distillation, run it a couple hours or so, and you are done. At the same time, I understand the convenience of having some ready though.

sbreheny - 12-9-2015 at 21:48

annaandherdad: I think you could be extra careful and make the cap last longer. How long, I don't know. I think the perfect thing would be if I could find a cap which was made of PTFE or Tefzel (ETFE?) and which matched the threads on an amber glass bottle.

One thing I noticed since my post - the amine odor I was referring to only happens if I touch the bottle and then smell the skin on my finger which contacted the bottle. If I smell the (closed) bottle itself, there is no odor. So, I really do think that this is a tiny amount of nitric acid on the surface and the odor is it denaturing the keratin of my skin. It must be that HNO3 or NO2 gas is very slowly diffusing through the PTFE bottle and then reacting with humidity in the air to form dilute nitric acid drops on the outside of the bottle. Very interesting!

KesterDraconis: I typically have only a few hours each weekend to do chemistry. I can't afford the time to make reagents right before I need them. I have stored 35% H2O2 for more than 18 months with no gas buildup (the plastic bottle doesn't even become rigid from pressure inside) BUT I keep it in the fridge, so that might make a difference. Also, when I recently tested the concentration of it by serial dilution followed by using peroxide test strips, I got a result which indicated that it is still at or near full strength, so it seems that refrigeration is the way to go for H2O2 storage. I have not noticed the HNO3 building up very much pressure, even though I store it at room temp.

ave369 - 12-9-2015 at 23:37

That's how I store concentrated nitric acid: in a bottle made of amber glass with a screw-on lid, but the lid is slightly modified. Under it, a coin tightly taped with PTFE tape from all sides is put. The lid is screwed tightly to ensure that the PTFEfied coin seals the bottle airtightly.

greenlight - 13-9-2015 at 06:10

I store my vacuum distilled 99% Nitric acid and 30% Hydrogen peroxide in these Schott Duran bottles. Nitric acid in the freezer and Hydrogen peroxide in a separate section in the refrigerator.
They aren't cheap but have had no problems at all using them.

[Edited on 13-9-2015 by greenlight]

KesterDraconis - 14-9-2015 at 05:23

Quote: Originally posted by sbreheny

BUT I keep it in the fridge,

Oh yes, that will make a it of a difference, I don't have a fridge you see

cyanureeves - 14-9-2015 at 05:57

i also have those amber bottles and one of the lids did not make it past 1 month before the middle totally caving in.i stored in another exact bottle but this time to protect everything else i put the bottle in a plastic coffee container with water in it.i thought it would at least make weak nitric acid if fumes got out again.the same bottle and cap has been in that folger's can for more than 1yr. now and the water is not acidic.last winter i opened the bottle and noticed it had turned a light green color and didnt fume at all.this summer i dissolved some gold and the acid was again yellowy and fuming. i made this acid about three years ago.

byko3y - 14-9-2015 at 06:12

greenlight, those bottles are dirt cheap, the reason why you've got them for high price is because there's Schott Duran label on them. There's more expensive and chemically resistant red caps with PTFE and ethylene-trichlorofluoroethylene seal http://www.vtrglass.cz/wpcproduct/bottle-reagent-with-red-sc... (10$ for 1L bottle in my country)

woelen - 14-9-2015 at 07:12

Quote: Originally posted by greenlight

I store my vacuum distilled 99% Nitric acid and 30% Hydrogen peroxide in these Schott Duran bottles. Nitric acid in the freezer and Hydrogen peroxide in a separate section in the refrigerator.
They aren't cheap but have had no problems at all using them.

[Edited on 13-9-2015 by greenlight]

Soring WFNA in such a bottle is fine, although the cap will deteriorate over time. I however, would never store H2O2 in such a tightly sealed bottle. H2O2 does decompose, even in a fridge and such a thick-walled bottle with thick-walled cap can be a nasty time-bomb. If such a thing explodes, then it will do a lot of harm!

I store my H2O2 in a bottle with a special cap, containing a check valve. You can easily make this yourself. Take a very fine drill (you can buy very small ones for drilling miniature holes in printed circuit boards) and make a 1 mm hole in the cap of the bottle and put some sticky tape over the little hole. This gives adequate protection for overpressure, while at the same time preventing unwanted thermal cycling from air (if the bottle cools down, then the tape is sucked against the cap and no air can get in). This mechanism works particularly well for H2O2, because this is not corrosive to the cap and the released gas (oxygen) is not corrosive to the tape.

greenlight - 14-9-2015 at 07:57

@Byko3y, I see I'm paying for the brand name haha, I think I will upgrade the blue cap bottle to a red ETFE sealed one like in your link for my WFNA from now though.

@Woelen, I have been venting the bottle and pressure is released every time but I will do what u said and drill a hole in it now with tape over it so i don't have to periodically open it all the time. Thanks for the tip.

[Edited on 14-9-2015 by greenlight]

aga - 14-9-2015 at 13:29

Why use Old, Stored reagents when you can have Fresh, New ones ?

I have some chloroform i made almost a year ago.
To Use it i will have to distill it again.

Storage in that case was pointless - it is not available for use right now, despite being in a bottle.

(yes, it has 1w% ethanol in there to prevent phosgene evolution)

alive&kickin - 18-9-2015 at 08:17

sbreheny, I have some type of film that seems to be resistant to acids and such (Pinkhippo11 testing now). If you want to send him a U2U, to see how things are working out, I'm sure he wouldn't mind. I would love to send you some so maybe you could put your nitric acid in a glass bottle with this film stretched over the mouth of the bottle with a plastic cap over that. Not so sure if it would work or not, but maybe worth a try?

Sulaiman - 18-9-2015 at 09:36

aga, according to Wikipedia https://en.wikipedia.org/wiki/Chloroform
you do not need to distil your aged chloroform
washing with saturated sodium bicarbonate solution will neutralise both the phosgene and HCl products.

[Edited on 18-9-2015 by Sulaiman]

ave369 - 18-9-2015 at 11:32

Recently re-bottled my fuming nitric acid into a narrow-necked amber glass bottle with a polyethylene bung and some plastic cap over it. It seemed to me better than the previous one because of the combination of bung and cap providing hermetic sealing. My store-bought hydrochloric acid also comes in such a bottle.

Anyone encountered severe corrosion of LDPE or HDPE bungs by nitric acid?

Sulaiman - 18-9-2015 at 13:26

Just checked: 69% HNO3 in suppliers (APC Pure / Atom Scientific) HDPE bottle
that I bought before September last year, has an expiry date of 7/2019.
I've not yet checked what 'expiry' means in this case.

aga - 18-9-2015 at 13:32

'Expiry' simply means that it might not be exactly 69% anymore, in this case.

Using the word 'Expiry' helps to sell more.