white nitric by ultrasound?

[ProdigyChild]

CO2 can be expelled from water by powerful ultrasound.
Why shouldn't it be possible to expel excess nitrous gases from concentrated nitric acid in order to obtain 'white nitric acid' :) ?

Ultrasound devices are easily available as living-room humidifiers creating strange looking cold steam.

100 people should have had this idea before me - why can't I find any post about it?

[Boomer]

Because you are a genius! :)

Only tests will show whether it works. The thing that makes me pessimistic is that CO2 is a gas dissolved in water under pressure. It probably is driven out by US in the same way it is driven out by shaking a coke.

In contrast, NA is a real solution, it is liquid at RT even if pure, plus it is hygroscopic. Moreover, the "strange looking cold steam" is no vapour but droplets thrust out by the shock waves.

Still worth a test IMO - it would be soooo convenient! :D

[FUTI]

yes as I remember CO2 suposedly should dissolve in water with chemical reaction and make carbonic acid and giving true solution with higher concentration then in some other solvent...but it dissolve in benzene and water in same amount so I guess this theoretical story that we are spoon-fed true school is bullsh*t. Ultrasound is used for chlorinated hydrocarbon removal in drinking water process units.

[Marvin]

Hmm, 2 thoughts occur. Firstly this seems like a high tech solution to a low tech problem, whats wrong with bubbling dry air or oxygen through nitric acid?

Secondly you are trying to expell nitrous gasses by accelerating the process that produces them and drives them out of solution, but you need to avoid accelerating the reaction that decomposes nitric acid producing oxygen and drives that out of solution. I have the feeling ultrasound will not discriminate too well.

[vurr]

H2CO3 is much much more unstable than HNO3...(well:shaking results for HNO ??)
Y gonna get near x% nitric ac mist from x% nitric ac with US

[FUTI]

to vurr: What I meant is that HNO2 and NO maybe can be removed by ultrasound as they are more unstable then HNO3. You are right about possible aerosolic dispersal of acid if device is not properly made and operated.

[vurr]

HNO2 decomposes readily with carbamide { (NH2)2CO } to N2 , CO2 , H2O / eliminating nitrous acid traces in orgsynth /
not sure about NO...

but is it suitable for HNO3 cleaning?

[FUTI]

I agree about adding urea remove HNO2...but it looks to me that US is easier way (you don't add nothing to mixture just do thermical/mechanical tretment). I believe that NO can certainly be removed by US being dissolved as neutral molecule more like chloroform or CO2, HNO2 is trickier in that way but energy supplied by US can decompose it.
It is not best idea to use US for HNO3 cleaning, but if you going to make a small scale production it will do the job.

[vurr]

ouF! it's NO2, that brown contaminant, that we want out...
and test shall be done to be sure.

solubility of NO is 7.4 ml/100g H2O @ 0C and 2,6 @ 100. presence should not hurt...
HNO2 - unstable;visual experiment:NaNO2 + HCl in water and heat,should decompose readily,showing lot bubbles.

================================================== ===

urea nitrate decomposes @ 152C
and giving off kind a acidific fumes(what? UN to urea+HNO3? without water)
over 16xC (???) ammonia starts form from pure carbamide...(smell)

[FUTI]

NO2 is the same thing that makes HNO3. When dissolved it makes HNO3 and HNO2 through disproportion. HNO2 as you said is not hard to remove, but I wondered will US shift the some balance. If some kind of balance formed in solution is responsible for reaction not going to completion maybe nitrite and NO removal can shift it to white nitric acid. Anyway NO2 is also a neutral molecule so US could possibly remove it to.

You are wrong about NO and HNO2 presence can't make any harm. HNO2 can change nitration ussualy by slowing it down. It also can alter the reaction mechanism from cationic to radical.

If you will use it for production of metal salt or urea nitrate then I guess it is safe because nitrite will decompose or they are more soluble then nitrate.

[vurr]

industrial:
a) 3 NO2 + H2O -> 2 HNO3 + NO (or maybe here should be = instead of -> ? reversable reaction?)
b) 2 NO + O2 -> 2 NO2

in b) O2 is from air,so adding US, esp.when mist is formed ,should affect formation of NO2 and over that affect also reaction a).

[FUTI]

Super!!!

This exchange of opinion finaly get some results. Congratulations vurr, you have just make fantastic remark. With this we could combine two strategies and possibly combine its effects/mechanism...both bubbling of the air and US.

Only problem that remains is acid aerosol formed but with some kind of particle removing design this can be overcome. Filter of some kind...glass frits, fiberglass curtain, some of those cyclonic filtering device. Anyone with idea?

[Mr. Pseudo]

If reaction is carried out in a sealed vessel, steam can be injected into the reaction chamber, and the resulting aqueous HNO3 condensed.

Say the reaction is carried out in a large roundbottom with a ground glass joint at the top. Set up an apparatus which will force steam into the beaker (perhaps through an insulated glass tube, and keep a small vent open to the air to release pressure. Reaction vesel could be submerged in cold water for cooling.

If it's impossible to get the bubbler into the flask while it's in a bath, you could probably just run cold water over it.

I don't think that any filtering device within our price range could effectively remove an acidic aerosol.

[meselfs]

Hmm, 2 thoughts occur. Firstly this seems like a high tech solution to a low tech problem, whats wrong with bubbling dry air or oxygen through nitric acid?

I don't think that would work. Industrially, clear nitric acid only forms when the oxygen/water/NO2/NA mix is subjected to 5 MPa (about 50 atm). But note: Common oxygen cylinders come fresh with around 14 MPa, so it may be possible to just wiegh the ingredients, put them in an aluminum cylinder (magically, NA doesn't attack aluminum), and add the oxygen under pressure.


Concerning the ultrasound, I think it might rid the acid of NO2, but that would leave behind around 60%-70% clear acid. The concentration never goes higher unless you do something drastic, eg apply pressure as previously noted.
But who knows, the awful high frequency shaking might work a miracle. Somebody with one of these ultrasonic things please try it :-> .

[Marvin]

The early part of the thread does not discuss increasing the concentration of the nitric, just getting rid of nitrous gasses to produce white nitric, a pinch of urea and dry air is a standard method for this. High pressure oxygen has been discussed in other threads, its extremely unlikley a pure aluminium container would be able to take 50 atm.

[meselfs]

Okay, sorry.

But don't be fooled... an aluminum tank definitely can withstand that. I've been doing pnuematics experiments since I was 12, compressed gasses are way overrated. I once made a pump that held back 15 atm without any noticeable leakage.

I've seen medical oxygen cylinders made of aluminum, and they are designed to hold back the 14 MPa that welding oxygen cylinders do.

[Meawoppl]

I think this whole concept is great, just as long as you have coated you humidifier in teflon. Humidifiers use peizoeletrics to make their high frequency vibrations. I am not to optimistic about the resistance to those materials to Fuming Nitric Acid. PZT ( a common peizo material) has to be manufactures under vacuum and other demanding conditions.

I do think however that if you set up a pair of peizoeletrics similar to that used in these sonoluminescence experiements, you might have a promising technique.
http://www.techmind.org/sl/#behaviour
Of particular intrest is the following quote:
"With very gassy water, small bubbles may form in the vicinity of the trapped bubble, and feed it, sometimes to the point of instability (bubble dissolves/rises to surface)"

[Meawoppl]

I have done some more research on that avenue, but most things I have come across tell me that "the mechanisim is not well understood" The bubble seems to form at antinodes of the standing wave, so I guess if you used the process to pull a bubble together, then turn it off, it may just float to the surface before being absorbed? Really this is more of an impractical mental exercise than something that would be economical. Those peizoeletrics are not cheap either, but if mounted outside the flask, they will basically last forever. I have some itty bitty ones, but no fuming nitric handy, I may give that a go at some point in the distant future.