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Author: Subject: Safety measures for working with NO2
BerthelotOnCrack
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[*] posted on 1-7-2021 at 03:05
Safety measures for working with NO2


Hello nitration experts,
I'm going to make some fuming nitric acid for nitrocellulose by distillating a mix of sulfuric acid and potassium nitrate. I'm aware this will produce a fair amount of NO2, which is really toxic.
My question is: even though I will do it outside, do I need to wear a respirator ? I do have the right filter, but should I use it ?

Excuse me if it sounds like a silly question but I have never worked with large quantities of NO2 and everywhere I read on it it says that it's a really nasty gas, so I prefer to ask.
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Oxy
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[*] posted on 1-7-2021 at 05:33


Do it with ventilation and preferably with scrubber (u can use 10-15% NaOH). Gas mask can be useful but if reaction will go smooth then scrubber should be enough.

Do not overheat the reaction as it will produce much of nitrogen dioxide

[Edited on 1-7-2021 by Oxy]
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BerthelotOnCrack
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[*] posted on 1-7-2021 at 05:57


Quote: Originally posted by Oxy  
Do it with ventilation and preferably with scrubber (u can use 10-15% NaOH). Gas mask can be useful but if reaction will go smooth then scrubber should be enough.

Do not overheat the reaction as it will produce much of nitrogen dioxide


Ok ventilation, would a fan be enough ? I'm in a totally opened space, I can afford to spill some NO2

Also I have already set up a trap but the NaOH + water solution tends to reflux in the distillated acid...

Finally, should I protect the apparatus from light ? I have heard that nitric acid was sensitive to light, but to which extent ?
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Herr Haber
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[*] posted on 1-7-2021 at 08:38


It's not a silly question if it prolongs your life.

The thing is that you shouldnt get any "fair amount" of NOx if you do it right. If you have time and plenty of ice for cooling doing it slower will *always* be better than faster. Plus, doing it faster gives you acid that is more red than white which is not desirable in most cases.
Forget the NaOH trap especially if you are outside. Put on the mask anytime you can though. If you've got a fan and can use it to push vapors away then by all means do it (change fan when the blade becomes yellow)

You will get some NOx while distilling but nowhere near what you'll get say... if your cellulose is contaminated with some fat.
I never thought it necessary to protect the apparatus from light. First, I can turn of the light in the room I'm distilling acid, second half of the apparatus is covered in Al foil.

One suggestion: if you voluntarily waste a few ml of HNO3 by allowing a reaction to heat up or by introducing impurities you'll have a clearer idea what is acceptable, what should be immediately crashed into water and what would require you to flee immediately.




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macckone
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[*] posted on 1-7-2021 at 21:07


nitric acid reacts with UV light. I would guess to some extent that would happen in normal sunlight.
As for how hazardous is NO2, the STEL is 5ppm.
For comparison HCN and HS is 10ppm.

The problem is that it forms nitric acid in your lungs, which as you can imagine is bad for you.
People who live in major cities eventually get emphysema from NO2 as do industrial workers exposed to it.
It causes chronic damage.
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Sulaiman
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[*] posted on 2-7-2021 at 05:56


If you can guarantee always being upwind then it's very safe
If you get a whiff of NO2, even enough to make you cough a little - you'll be ok
I'd have the fan behind me blowing towards me while I'm facing the experiment which is downwind of me.




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BerthelotOnCrack
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[*] posted on 2-7-2021 at 07:57


@Herr Haber
@Sulaiman
Thanks for these valuable indications, I will buy a big fan and do it on windless day, keep the temp at 83°C and cool the recieving flask.

Just a question about the respirator... I am used to it for acid vapors and chlorine because when the filter is dead you just can't breath, so there is no ambiguity about when to change it, however for CO and NO2 there is a precise operating time, which is for my filter 20mn... do I really have to use it *only* this much ? How do you cope with the number of filters you need for longer expositions ?

@macckone
I intend to cover everything with Al foil
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macckone
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[*] posted on 2-7-2021 at 11:50


The ratings on filters are pretty conservative.
The time is at the maximum concentration rating of the filter.
It isn't exactly linear because CO2 is also acidic from the filter's viewpoint.

As others have mentioned, doing it outside and avoiding the cloud is generally sufficient.
Be aware of the suction vortex created around a stationary object near clouds.
Ie. the campfire smoke always blows towards you.

With nitrocellulose, you can be close by but for more advanced nitrations, you want to put some distance between you and the reaction.
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[*] posted on 16-9-2021 at 19:26


NO2 fumes will take your breath quick. Be careful. I've been making small quantities of WFNA lately, and pull vacuum through a trap, and the exhaust vent on my vacuum pump is vented outside through a hose. Believe if I had a glassware episode during this particular distillation, I'd grab my dog and flee. Worry about cleanup when i could breathe.................



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