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Author: Subject: Nitric acid
JJay
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[*] posted on 15-8-2020 at 01:09


If you know what you're doing, you can do it inside, but I strongly advise against it unless you have done it outside or in a fume hood several times previously. The fumes are not as bad as you'd expect, but they are to be completely avoided.
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[*] posted on 15-8-2020 at 01:42


Quote: Originally posted by JJay  
If you know what you're doing, you can do it inside, but I strongly advise against it unless you have done it outside or in a fume hood several times previously. The fumes are not as bad as you'd expect, but they are to be completely avoided.


Glassware can still crack unexpectedly. Spills of hot nitric acid inside are absolutely no joke man.

I'd argue that nitric acid fumes are pretty much as bad as you'd expect. If you are hovering over a cleanup inside because something went wrong, holding your breath, you're going to have to inhale at some point. Running back and forth to the window isn't something that works when you need to contain something ASAP. The acid fumes can be filtered using a 3M respirator with the proper filter, but the NO2 doesn't get filtered very well at all. Speaking from experience here. NO2 in low concentrations is okay for the filters to handle but even small puffs of concentrations that have red color to them are not filtered well at all and are very pungent.

Highly advisable to never distill nitric acid in a poorly ventilated area indoors.
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JJay
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[*] posted on 15-8-2020 at 02:15


Do you know what nitric acid does when it's spilled?
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fdnjj6
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[*] posted on 15-8-2020 at 03:03


Quote: Originally posted by JJay  
Do you know what nitric acid does when it's spilled?


When hot, it'll give off choking vapors. When my distillation leaked, it destroyed 2 keck clips and rusted a clamp.

With heat it decomposes to NOx gases.

It's an acid and so it will attack lots of materials. A good amount of metals will react with it and create more NOx gases.

If you have an oil bath, it could potentially react with it too if fuming. I doubt conc. will.

Indoors is just a bad idea man.

Unless in a fume hood.

[Edited on 15-8-2020 by fdnjj6]
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JJay
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[*] posted on 15-8-2020 at 03:22


It bleaches surfaces. Even one drop of spilled nitric acid will leave an unsightly stain on a dark countertop.

Nitric vapors are pretty nasty but not as bothersome as hydrogen chloride or sulfur dioxide. It's like stepping on a nail rather than being stabbed or shot. Don't step on nails, and don't breathe nitric acid vapors.
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[*] posted on 15-8-2020 at 03:32


Yea that makes it worse. It gets deeper into the lungs. I had a good breath of HCl while cleaning stubborn glassware. It causes an instant relfex for me. Ammonia even more so. Nitric acid? Not really. There's still burning and stuff but it's not impossible to breathe in deeply. If you do this inside, fume hood, or a good respirator on hand and no one else in the lab/house/wherever you do stuff. Accidents happen.

Obviously good ventilation as well. Or deal with it when shit hits the fan lol.

For all tense and purposes it's you who is in danger. Don't put others at danger and you can do whatever you please with your acid distillations.

[Edited on 15-8-2020 by fdnjj6]
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JJay
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[*] posted on 15-8-2020 at 06:18


You might have a good point there, actually. I don't see any clear answers on that subject in the data. Of course, I am talking about small, brief exposures...

5 mg/m^3 is considered unsafe over a long period of time... in a small room, that would be about 150 mg, vaporized, dispersed and unventilated... 50 mg/m^3 would be starting to get dangerous on a short timeframe, and 500 mg/m^3 would be actually dangerous....

A good-sized distillation might actually release 15 mL or so of nitric acid vapor... that's enough to be seriously dangerous in a small, unventilated room....

It's definitely not something a person would breathe willingly if conscious and able to escape.

I have distilled it inside and without using a fume hood on a 500 mL scale lots of times. Of course, that was with a bunch of chalk powder ready at hand and with ventilation, not to mention a gas mask and a powerful window fan nearby. The only time I caught a whiff of the vapors was the time I did it in a fume hood without turning on the fan. It wasn't choking, really. The air just had a sour smell and taste. I immediately turned on the fan and had no issues.

I would suggest starting with a smaller amount, maybe 100 mL, and using a fume hood.
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[*] posted on 16-8-2020 at 03:54


This seems a good place to post the weekend's activities.

I needed to distil some nitric acid – it has been a long time since the last one. I have normally used KNO3 and H2SO4. However…

Following guidance from Nurdrage's latest offering I decided to try dry distillation of nitrate salt and sodium bisulfate. I know that Tdep uses a similar method with bisulfate but IIRC he adds water to the mix.

My attempt was pretty much a failure:
  • high evolution of NO2
  • lots of foaming
  • not able to get up to azeotrope temp of 120°C without foam-over
  • small batch because of foaming issues and incredibly slow

    I ended up dismantling the apparatus and removing half of the charge before continuing. Still no joy.
  • I was able to get to temperature but distillation was still slow until it stopped
  • Only a few mL of the reddest HNO3 I have ever seen recovered.


    My conclusion is that I will not be able to use this method to produce HNO3 at the scale I need.
    KNO3 is not NaNO3. It seems that Nurdrage had a lot more success than I using the sodium salt. Not nearly the same amount of foaming and much better evolution of product.


    It is worthy of note that I was working indoors without a fume hood. My lab space is pretty well vented but is still not a place that I want to fill up with toxic gases. I was able to rig up effective gas scrubbing and proceed at the rate I did without seeing or smelling any gas. And even when I had to pull apart the equipment to restart I managed to accomplish this with only a couple of small puffs of NO2 escaping – only enough to smell faintly. This was accomplished with (a) a good trap system, (b) allowing everything to cool before opening (c) judicious use of stoppers and (d) venting the reaction flask over a sink with a spray of water. I would have only had NO2 and no HNO3 vapours going into the atmosphere. It is good to know that it is possible to manage the risks satisfactorily.
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    Herr Haber
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    [*] posted on 16-8-2020 at 05:27


    Quote: Originally posted by fdnjj6  

    And by the way depending on the solvent you're exposing them to, you really should change your ways. Ethanol? Meh. Toluene? Eehhh. Chloroform? No. Carbon tet? No. Benzene? No. Bromine (not a solvent I know)? No. You see what I mean? I'm not some lunatic contrary to what people thought of me in my previous post. I'm trying to help myself and others be responsible.


    What's the most common solvent you can find in kettles in a common work environment ?
    You've just been DHMO'd :D:D:D:D




    The spirit of adventure was upon me. Having nitric acid and copper, I had only to learn what the words 'act upon' meant. - Ira Remsen
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    [*] posted on 16-8-2020 at 05:34


    Quote: Originally posted by fdnjj6  
    I've got a question for all of you.

    Do you do this outside? And how close are your neighbors and how close can someone come to your distillation?


    Outside on my porch. Closest neighbor is about 1 km away. I can make as large and toxic clouds as I want. ;)
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    [*] posted on 16-8-2020 at 05:45


    Quote: Originally posted by j_sum1  
    This seems a good place to post the weekend's activities.

    My attempt was pretty much a failure:
  • high evolution of NO2
  • lots of foaming
  • not able to get up to azeotrope temp of 120°C without foam-over
  • small batch because of foaming issues and incredibly slow

    I ended up dismantling the apparatus and removing half of the charge before continuing. Still no joy.
  • I was able to get to temperature but distillation was still slow until it stopped
  • Only a few mL of the reddest HNO3 I have ever seen recovered.


    My conclusion is that I will not be able to use this method to produce HNO3 at the scale I need.
    KNO3 is not NaNO3. It seems that Nurdrage had a lot more success than I using the sodium salt. Not nearly the same amount of foaming and much better evolution of product.



  • Odd. I have had great success with using bisulfate with my rather crappy setup, although I have also used NaNO3, mainly because KNO3 through the sources I have is 3x the cost.

    I don't consider high NO2 evolution to be an issue. I make sure to have my condenser cold enough to liquefy the NO2 as well. Lots of ice and water. Sometimes salt water to get a few degrees below freezing. Since I use a spiral condenser, it has plenty of time to react with water and oxygen to become nitric acid by the time it reaches the bottom. I always have a ton of NO2 at the top, but very little comes out at the bottom, and I would add that the distillate is rarely red at all, pretty much always light yellow. It does fume NO2 though.

    People always complain about the foaming of this process, yet I've never even seen it foam, like at all. Do you have any water in the mix? I always run it dry and just slowly work my way to melting all of it.
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    JJay
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    [*] posted on 16-8-2020 at 10:20


    I'm going to have to give the bisulfate method a try and see if I can get it to work....

    I've never actually scrubbed the gases from a nitric acid distillation. I just run a vinyl hose outdoors from the distillation adapter outlet. The hose material is important. Do not use a latex hose for this purpose; it will be destroyed. The nitrogen oxides and nitric acid vapor do attack pvc, but they attack it very slowly, so one hose can be used for probably dozens of runs. A vinyl hose will be virtually undamaged after one run except for some discoloration.
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    Fyndium
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    [*] posted on 4-11-2020 at 09:19


    I acquired a sample of HNO3. It is declared as azeotropic 68% and it's crystal clear. The thing is it fumes very strongly of white fumes. Is this normal for azeo HNO3? I had no chance to measure SG.
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    [*] posted on 4-11-2020 at 09:26


    Yes, azeotropic HNO3 fumes slightly. I usually use a volumetric pipette and balances for density measurement.
    OK, "stronly" and "slightly" are relative characteristic I assume.
    I mean it's not a thing I need a gas mask to open the bottle. 36% HCl fumes MUCH more.


    [Edited on 4-11-2020 by teodor]
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    [*] posted on 4-11-2020 at 10:50


    Quote: Originally posted by teodor  

    I mean it's not a thing I need a gas mask to open the bottle. 36% HCl fumes MUCH more.


    [Edited on 4-11-2020 by teodor]


    The gallon of 31.5% HCl that I bought at the hardware store fumes like crazy, I won't even open it indoors anymore.

    Cutting the concentration in half helps a lot, thanks to the kind sciencemadness person who recommended this in a different topic.
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    [*] posted on 4-11-2020 at 11:07


    I think the volume in the bottle also plays some role. I just distilled 20ml of azeotrope from the last batch, so it fumes only as 20 ml I assume ... and if you have 1 l bottle you probably have a bigger problem.

    It is not correct to compare 31.5% HCl and 36% HCl, the last one has 4.5 times bigger vapour pressure. And 38% twice as 36%.
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    Fyndium
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    [*] posted on 4-11-2020 at 11:37


    It fumed pretty much as 33% HCl. I repacked some of my reagents so I handled both. The ambient temp was likely around 15C.
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    [*] posted on 4-11-2020 at 11:58


    Fuming strongly depends on the relative humidity. I have a hygrometer in my greenhouse and out of interest I checked the fuming of different acids when the humidity was around 30% and when it was 95%. This makes a world of difference. I never actually saw 96% sulfuric acid fume, but with the high humidity even this produces fumes.

    [Edited on 4-11-2020 by Tsjerk]
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    [*] posted on 4-11-2020 at 12:58


    Here in the UK possession and sale to unlicensed individuals is illegal above certain thresholds, 3% for nitric acid and 15% for sulphuric, both a pretty much impossible to buy unless through sigma or similar with the correct license. Link to the gov page https://www.gov.uk/government/publications/licensing-for-hom...



    Green QD's so far

    Feel free to correct grammar or incorect knknowledge. We are all learning.
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    teodor
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    [*] posted on 4-11-2020 at 13:05


    So, I assume people in UK were forced to switch to dinitrogen pentoxide and oleum.
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    [*] posted on 4-11-2020 at 13:09


    This 3% and 15% limit applies to whole EU. Silly, if oleum and dinitrogen pentoxide are still free to go, in that context.

    Meanwhile, they are now restricted to dihydogen monoxide, although EU has plans on regulating it's use as well.
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    teodor
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    [*] posted on 4-11-2020 at 15:03


    I am wondering, will the distillation of 15% H2SO4 with some nitrate give HNO3 or at this starting concentration 2 acids will be distilled together, even had idea to check this but still didn't.
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    [*] posted on 4-11-2020 at 15:18


    HNO3 azeotrope distills at 120C, H2SO4 either does not bring water with it or keeps it, but not 15%. I suppose it will hold of part of that water.

    Could one use desiccants to hold the water and distill (more) concentrated HNO3 this way?

    And for the record, HCl should work with nitrates for HNO3, and sodium bisulfate is the classic.
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    [*] posted on 4-11-2020 at 15:32


    But I don't bother about HNO3 concentration, I am curious about the percentage of H2SO4 to HNO3 in the result.

    HCl is not a good idea as for me, HNO3 and HCl requires chemical separation (distillation with AgNO3 as a classical method).


    [Edited on 4-11-2020 by teodor]
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    [*] posted on 4-11-2020 at 23:38


    OK, I think I found the answer.
    http://www.personal.psu.edu/mrh318/Gmitro-Vermeulen-AICE-196... , figure 6.
    The vapor pressure for H2SO4 is almost unchanged in the 0%-40% concentration range so really, the longer boiling (lower starting H2SO4 concentration) means more H2SO4 will be distilled, but still it is below 0.2%, so practically is not a trouble.

    [Edited on 5-11-2020 by teodor]
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