Sciencemadness Discussion Board

Nitric acid

nezza - 3-11-2015 at 02:34

As it is impossible to buy nitric acid of any sensible concentration within the EU currently I thought I would have a go at a synthesis. I know distilling alkali nitrates with sulphuric acid is a well known route but sulphuric acid is also unavailable so I tried distilling syrupy phosphoric acid with potassium nitrate using a glass retort until oxides of nitrogen became obvious in the retort. This yielded a very pale yellow liquid which reacted as expected with a copper coin. It fumes slightly in moist air and gives a very faint opalescence with silver nitrate so may contain some phosphate carried over. On titration it calculates as 12.5M in strength.

woelen - 3-11-2015 at 08:18

Interesting to read that phosphoric acid can be used as well. How well did your glassware withstand the phosphoric acid? I read that hot phosphoric acid tends to corrode glass vessels and if this is true then that may reduce the usefulness of the method.

I did not expect that sulphuric acid would become unavailable. In the Netherlands it still can be purchased. The new EU regulations only are for nitric acid (and 6 other non-acid compounds). As far as I know, citizens still may buy and use sulphuric acid. The only thing is that unusual transactions (e.g. purchase of very large amounts) need to be reported.

deltaH - 3-11-2015 at 12:25

Very nice, makes me wonder whether using calcium nitrate (a common fertiliser) and phosphoric acid might work even better because of the low solubility of the product salt.

ave369 - 4-11-2015 at 14:59

Of course phosphoric acid does work, it is not volatile, just like sulfuric. I've tried substituting it for sulfiric when making both HNO3 and HCl, both times it worked like a charm.

But you better do not use glass retorts for this, this glassware is too good to waste it like that (hot phosphoric acid!). Use some cheap ass flask and a condenser.

nezza - 5-11-2015 at 00:47

Thanks for the warnings re glass and phosphoric acid. I have not noticed any problems with corrosion of the glass yet, but I'll keep an eye on it.

Mesa - 5-11-2015 at 13:43

The etching of glass with phosphoric acid is much less significant than, i.e. molten NaOH/KOH. It takes prolonged contact at elevated temps to get noticable damage(it starts to look like frosted glass.)

It will weaken the glass over time/repeated uses though so like others have said, avoid using any glassware you wish to keep around.

tahallium - 28-7-2020 at 15:02

Can I make nitric acid without distillation using calcium nitrate and phosphoric acid?

Bedlasky - 28-7-2020 at 22:42

Calcium dihydrogenphosphate have solubility 2g/100ml. So if you don't mind some calcium and phosphate contamination, yes.

Whathappensif - 28-7-2020 at 23:29

Quote: Originally posted by woelen  
The only thing is that unusual transactions (e.g. purchase of very large amounts) need to be reported.


Is the reporting done with the customer's consent (so you fill in a form saying why you need it) or is it done quietly without the knowledge of the customer?

What about what retailers consider "suspicious" enquiries, such as purchases of large quantities to residential addresses or even business addresses that have no use for those chemicals, like 100L of conc. H2SO4 going to a hair salon? :o

Fyndium - 29-7-2020 at 00:52

In UK acids are restricted because of acid attacks by all kinds of gangs.

I think it's great to have alternatives to sulfuric acid. It's great to always have alternatives in chemistry, because many times you've got already the reagents when you substitute a little. I hate it when synthesis specify a certain type of reagent or solvent and later I find out that some other reagent could have worked very well which I already had.

Btw if you need to use sacrificial glass, chinese glassware is perfect for that. They are quite high quality but cheap.

[Edited on 29-7-2020 by Fyndium]

Junk_Enginerd - 30-7-2020 at 11:13

Quote: Originally posted by Whathappensif  
Quote: Originally posted by woelen  
The only thing is that unusual transactions (e.g. purchase of very large amounts) need to be reported.


Is the reporting done with the customer's consent (so you fill in a form saying why you need it) or is it done quietly without the knowledge of the customer?

What about what retailers consider "suspicious" enquiries, such as purchases of large quantities to residential addresses or even business addresses that have no use for those chemicals, like 100L of conc. H2SO4 going to a hair salon? :o


In sweden at least, and I would suspect the rest of the EU as well, you cannot buy any amount of sulfuric acid privately, unless you have a permit. The permit is actually no big deal from what I've read, you just need to show you have the knowledge and the right conditions to handle it. You pay a relatively small sum(like 200€ as I recall it), and present your case and why you need it, it gets reviewed and either denied or approved. I'm actually thinking about applying for this as I honestly think that hobbies which require sulfuric acid is a valid enough reason to be approved. This rule is probably just to deter those who would abuse it and make them feel like it's not worth the hassle.

Anyway, no need for sulfuric acid for HNO3 distilling. Sodium bisulfate works a charm, and is at least here widely available even in grocery stores as pool ph adjuster.

[Edited on 30-7-2020 by Junk_Enginerd]

Felab - 30-7-2020 at 13:15

Over here in Spain sulphuric acid is not regulated at all and sold to individuals. Nitric acid used to not be regulated as well but now you apparently need a license to buy it. I still have a half-full bottle of 60% HNO3 that I bought online a while ago.

It seems hilarious (at least to me) that they regulate the sell of nitric acid because of it beeing an explosives precursor, anybody who has the knowledge to make explosives with HNO3 will almost certainly have the knowledge to make it from scratch.

Also, they should probably target more things like hexamine instead of nitric acid.

Fyndium - 31-7-2020 at 00:49

It's intended to make the lowlife thugs lifes difficult. I don't know how many child blow up their hands and eyes with homemade explosives every year but I've been in impression that the number is dozens in Europe. An involved chemist will churn basically any chemical from anything.

Does anyone have any notes about bisulfite nitric acid? What are the reaction conditions? I've made HNO3 from sulfuric acid and a nitrate a long time ago few times with ease, but if I happen to need a reagent for nitrations it might come in handy due to being so OTC.

Whathappensif - 1-8-2020 at 06:08

Quote: Originally posted by Junk_Enginerd  
The permit is actually no big deal from what I've read, you just need to show you have the knowledge and the right conditions to handle it.
[Edited on 30-7-2020 by Junk_Enginerd]


By definition, if you need to provide something beyond nothing then it is only to your detriment. The question is how much is that cost going to be.

It used to be that Jewish people needed to register before Concentration Camps were set up. And then the murdering started and there was no where to run. It won't be as severe as this but what do you think the police will do, if there is a terrorist attack using nitrated organics and they had a list of all the people buying HNO3/H2SO4?
Quote: Originally posted by Felab  
Over here in Spain sulphuric acid is not regulated at all and sold to individuals. Nitric acid used to not be regulated as well but now you apparently need a license to buy it. I still have a half-full bottle of 60% HNO3 that I bought online a while ago.

It seems hilarious (at least to me) that they regulate the sell of nitric acid because of it beeing an explosives precursor, anybody who has the knowledge to make explosives with HNO3 will almost certainly have the knowledge to make it from scratch.

Also, they should probably target more things like hexamine instead of nitric acid.


Is possession of HNO3 without a license illegal in these countries (Sweden, Spain, UK, etc.?) Or is just purchase without a license? If you made HNO3 on your own like through the Birkeland-Eyde Process is it illegal?
Quote: Originally posted by Fyndium  
It's intended to make the lowlife thugs lifes difficult. I don't know how many child blow up their hands and eyes with homemade explosives every year but I've been in impression that the number is dozens in Europe. An involved chemist will churn basically any chemical from anything.

Does anyone have any notes about bisulfite nitric acid? What are the reaction conditions? I've made HNO3 from sulfuric acid and a nitrate a long time ago few times with ease, but if I happen to need a reagent for nitrations it might come in handy due to being so OTC.


Politicians want to be seen to do something when terror attacks happen. It doesn't matter whether the reality is that what they do is ineffective in preventing most future attacks.

It is like jails too. Politicians want to be seen to be tough on crime so they throw people for small things into prisons run by for-profit companies, so incarceration rates go up. The USA has the highest incarceration rate in the world 655/100k people.

The benefits of home experimentation is not so easy to quantify because their benefits are personal satisfaction (which society cares f- all about), possible synergies with work and new innovations/discoveries (<- society can't miss what you don't know they don't have)

As for kids doing stupid things, well why should my freedoms be curtailed because of someone else's stupidity? Maybe the reason why there are so many idiots around these days is because we keep on interfering with Darwinism.

[Edited on 1-8-2020 by Whathappensif]

AJKOER - 3-8-2020 at 14:03

Per a preparation thread of mine and here https://www.sciencemadness.org/whisper/viewthread.php?tid=87... , Oxalic acid works to liberate an an acid from the underlying salt.

However, H2C2O4 may be control these days in select jurisdictions.
---------------------------------------------------

Whathappensif:

Don't worry too much about idiots in chemistry.

First mistake, they experiment with energetics in too large a scale (one should treat all energetics like there are drops of a HE).

Second, clueless and accidentally prepare large amounts of toxic gas indoors.

Third, create/experiment carelessly with highly flammable gases/liquids/solids (as in thermites) , with obvious consequences.

Fourth, when a substance is described as 'highly toxic', your goal in life should be to avoid it, and not attempt to prepare it.

Fifth, trying to ID an unknown gas by repeated inhalations, is far from the best/safest path.

......

Darwinism at its finest.

[Edited on 3-8-2020 by AJKOER]

macckone - 3-8-2020 at 15:55

Oxalic acid can be made by oxidizing ethylene glycol.
The usual method is nitric acid but there are large range of ways to do it.
peroxides and permanganates are two options.
manganese dioxide and air at close to boiling should also do it (haven't tried that one).
Finally there is always extraction from rhubarb.

symboom - 3-8-2020 at 18:17

In relation to the synthesis of nitric acid
https://m.youtube.com/watch?v=CqzrTxshOXM
Nurdrage video on using sodium bisulfate and sodium nitrate


I did not know that although oxalic acid as a cleaner is getting more popular now. The last synthesis I've seen is nitric acid and sugar which seems like a waste of nitric acid

Historically oxalic acid was obtained exclusively by using caustics, such as sodium or potassium hydroxide, on sawdust

Pyrolysis of sodium formate decomposes to form sodium oxalate and hydrogen then is converted converted to oxalic acid.

Sodium formate
reacting chloroform with an alcoholic solution of sodium hydroxide

Sodium formate may also be created via the haloform reaction between ethanol and sodium hypochlorite in the presence of a base. Also is the preparation of chloroform using alcohol instead of acetone



[Edited on 4-8-2020 by symboom]

Junk_Enginerd - 5-8-2020 at 11:23

Quote: Originally posted by Whathappensif  

By definition, if you need to provide something beyond nothing then it is only to your detriment. The question is how much is that cost going to be.

It used to be that Jewish people needed to register before Concentration Camps were set up. And then the murdering started and there was no where to run. It won't be as severe as this but what do you think the police will do, if there is a terrorist attack using nitrated organics and they had a list of all the people buying HNO3/H2SO4?

Is possession of HNO3 without a license illegal in these countries (Sweden, Spain, UK, etc.?) Or is just purchase without a license? If you made HNO3 on your own like through the Birkeland-Eyde Process is it illegal?


Politicians want to be seen to do something when terror attacks happen. It doesn't matter whether the reality is that what they do is ineffective in preventing most future attacks.

It is like jails too. Politicians want to be seen to be tough on crime so they throw people for small things into prisons run by for-profit companies, so incarceration rates go up. The USA has the highest incarceration rate in the world 655/100k people.

The benefits of home experimentation is not so easy to quantify because their benefits are personal satisfaction (which society cares f- all about), possible synergies with work and new innovations/discoveries (<- society can't miss what you don't know they don't have)

As for kids doing stupid things, well why should my freedoms be curtailed because of someone else's stupidity? Maybe the reason why there are so many idiots around these days is because we keep on interfering with Darwinism.

[Edited on 1-8-2020 by Whathappensif]


You have some very ingrained, very American thinking. Civilians who aren't up to no good aren't persecuted here. Shit, most of the time I *have* been doing illegal things that certainly would have warranted a ticket or worse, and been caught doing it, it has always been a matter of "Well... does this guy actually have any malicious intent or did he just forget to consider this wasn't the best idea? Nah okay, dude, just don't do that, yeah?"

I've honestly not even heard of anyone that was punished for a harmless technicality here.

I don't think posession is illegal, but I honestly don't know for sure. I do know however, that there's zero possibility I'd ever face legal action for possession. Worst case I could imagine, if police for some strange reason would ever find it in my possession, I'd explain I'm a weirdo engineer with nerdy hobbies. I'm absolutely certain they'd shake their heads, laugh at me and tell me I should be careful.

I don't even think purchasing it is illegal. Selling it to unlicensed people is though.

While it's gotten worse lately, I gotta say that swedish politics is not anywhere near the beauty pageant or popularity contest that US politics seems to be from here. Making useless decisions and power moves in the name of "war on terror" etc doesn't fly here.

Well. Kids doing stupid things is a fact... And I can understand how the same society/government that sweeps up the pieces of said kids and pays for the damage would prohibit the means for that.

I honestly think the license solution is a decent compromise if I have to be adult about it. I don't like it, because I want my chemicaaals, but I can see how maybe it's for the best, since the license in question doesn't actually seem hard to acquire for a serious individual.

Mateo_swe - 8-8-2020 at 10:29

If you are in EU you can order sulphuric 95%, nitric 60% and most other acids online.
Some require a copy of ID as its 18 year limit and a few require a filled in form with description of intentional use.
But otherwise no problems, just order and its get delivered to the door.
Im in Sweden too and its no problem order sulfuric acid or any other acids.
There is no customs on deliverys inside EU so ordered chemicals will not pass customs.

But if ordering isnt an option you could always make the nitric acid.
I would not recommend to try this without some lab experience as there are nasty fumes.
One can easily lead the fumes away but one should always take into consideration that unexpected accidents can happen.
A kitchen full of NO2 gas isnt fun at all.
Here are a video with preparation of nitric acid using the bisulfate method that doesn't need sulfuric acid.
He make a mistake and ruin the nitric acid in the video but that is easily prevented from happening.
https://www.youtube.com/watch?v=VLOY-Jp2w1I


[Edited on 2020-8-8 by Mateo_swe]

fdnjj6 - 14-8-2020 at 07:17

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?

Herr Haber - 14-8-2020 at 07:53

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?


A question, not insults. That's an improvement.

To answer your question, I often gas people with solvent vapors at work. I actually let them come very close to the boiling solvent and people burn themselves regularly.
I know it'll annoy people (on Reddit!) but I dont feel responsible at all.
After all, it's my bosse's responsability: he bought those new kettles !

fdnjj6 - 14-8-2020 at 11:44

Well at first in that thread I was trying to seriously help people and be civil but when met with such backlash being called a sissy, a bitch, a chemophobe, an asshole, and being laughed at by people whom the post didn't even concern, I'd argue that would make almost anyone pissed and insult them. I put a lot of time into that post and it was purely to help others not get in trouble, keep people safe, not have issues with neighbors, and not have to deal with the consequences like I did becuase I know for a fact that many people do things exactly like me and often even worse with less precautions. So I hope it was understandable that I was outraged. I admit I went a bit overboard and took things quite a bit too personally (life's not the best right now) but I was extremely fustrated and mad at how me trying to help would cause me to be bashed to pieces by people whom like I said, the post didn't even concern since they run heir labs so well (apparently). I don't care to expose myself to the chemicals, it's about others around me that I was getting at. I'm fine dealing with the consequences of my actions, I'm not fine with having others deal with the consequences of my actions. Does it kinda make more sense now?

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.

arkoma - 14-8-2020 at 12:49

I like to use carbon tet to dissolve my iodine crystals--much easier to intravenously administer it. I find 3cc's injected while enjoying a chloroform cocktail really helps me unwind after being exposed to whingers.

And I have distilled HNO3 (H2SO4 + NaNO3 method) more than once in my lab. Which is in my living space. Greased joints, metal keck clips, and a double necked receiving flask work great. The second neck is for the hose barb fitting, so I can like, you know, vent the damn rig outside. I'm just a dumbass redneck though..............

JJay - 15-8-2020 at 00:04

Quote: Originally posted by arkoma  
I like to use carbon tet to dissolve my iodine crystals--much easier to intravenously administer it. I find 3cc's injected while enjoying a chloroform cocktail really helps me unwind after being exposed to whingers.

And I have distilled HNO3 (H2SO4 + NaNO3 method) more than once in my lab. Which is in my living space. Greased joints, metal keck clips, and a double necked receiving flask work great. The second neck is for the hose barb fitting, so I can like, you know, vent the damn rig outside. I'm just a dumbass redneck though..............


I like to put a condenser on the second neck to try to capture as much nitric acid as possible during the end phase when the contents of the boiling flask crystallize and throw off a lot of nitric acid vapors. Anyone reading this who wants to make nitric acid is advised to start with a small batch.

I understand that getting splashed in the eyes with nitric acid is somewhat less pleasant than getting a little chloroform or benzene in them.


[Edited on 15-8-2020 by JJay]

Mateo_swe - 15-8-2020 at 00:17

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?


Regarding the Nitric acid preparation in the video i linked.
This must be done either outside or in a flowhood.
It could be done inside but its very stupid and risky to do so.
If something breaks you would have the very nasty fumes inside and you would not be able to be inside to try vent the fumes without a gasmask.
These fumes will badly damage your lungs if inhaled so just do it outside if you want make nitric acid this way.
If doing the procedure correctly it will not be much fumes as most are dissolved in the water at the end of the PTFE tube and it will not be any problems to be around the procedure as long nothing breaks or a tube pops off.
If something unexpected happens, a flask breaks or a tube pops off there will be fumes but they will be dissolved in the outside air and they will not be any threat to neighbors except smell.

JJay - 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.

fdnjj6 - 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.

JJay - 15-8-2020 at 02:15

Do you know what nitric acid does when it's spilled?

fdnjj6 - 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]

JJay - 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.

fdnjj6 - 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]

JJay - 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.

j_sum1 - 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.

    Herr Haber - 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

    Junk_Enginerd - 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. ;)

    Junk_Enginerd - 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.

    JJay - 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.

    Fyndium - 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.

    teodor - 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]

    MidLifeChemist - 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.

    teodor - 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%.

    Fyndium - 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.

    Tsjerk - 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]

    Housane - 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...

    teodor - 4-11-2020 at 13:05

    So, I assume people in UK were forced to switch to dinitrogen pentoxide and oleum.

    Fyndium - 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.

    teodor - 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.

    Fyndium - 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.

    teodor - 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]

    teodor - 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]

    teodor - 5-11-2020 at 00:29

    @Housane so, to stay legal, I suppose, we need either method of direct HNO3 distillation of required concentration into the reaction flask or usage of salts like Pb(NO3)2 which liberates highly concentrated HNO3 by action of HCl/H3PO4 or application of NO/NO2 mixture in gaseous/liquid form or in a solution (which is not formally HNO3 anymore). So, I suppose if we want to share our experience with members of general public we need rewrite experiments of chemical demonstrations by usage on of these techniques.

    [Edited on 5-11-2020 by teodor]

    woelen - 5-11-2020 at 01:55

    In many cases this is highly impractical. Imagine yourself making copper nitrate by distilling HNO3 directly into copper wire, with all the issues of back-pressure, due to formation of NO2 from the metal. It also is difficult to control the amount of acid added.

    What I personally do is distill HNO3 from H2SO4 and NaNO3 (and in the future I certainly will try the NaHSO4 + NaNO3 method), but I only make small amounts (using a 100 ml boiling flask and a 50 ml receiver flask). This allows me to make some acid in a relatively short amount of time, and I make a few tens of ml. That amount I use in a few experiments. No need to make huge quantities and keeping those around. The experiments, however, I do with the prepared acid, I never distill straight into the reaction mix!

    As an added nice side effect, this strategy also reduces the risk considerably. If an accident happens with my distillation setup, it is unpleasant, but not a disaster. Things will be very different if you have half a liter of concentrated hot fuming acid and something nasty happens with that.

    I also noticed that the foaming problem with distillations is dependent on the source of the nitrate used. I have NaNO3 (so-called 99% chili salpeter, purchased as fertilizer in a 25 kg bag several years ago). If I use this directly, I get a lot of foaming and a lot of NO2. The granules are somewhat greasy, I think they are covered by some wax-like substance to make them less hygroscopic. What I did is dissolve several hundreds of grams of this NaNO3 in water, which leads to a turbid solution, with a lot of scum on the surface. I let the crap settle at the bottom and then I carefully siphon 90% or so of the liquid into a clean pan. The rest of the liquid (insoluble crap at the bottom + scum at the surface) I discard. The solution of NaNO3 in the pan I evaporate and let it dry (not perfectly, but for my distillation, this is not important, the acid concentration still is well above azeotropic concentration). This cleaned NaNO3 only causes little foaming in the distillation. I do not use all this cleaned NaNO3 in one distillation. I keep it around as clean stock of NaNO3 and if it is used up, I make a new clean batch. Up to now, I only have done this twice, so I have a life-time stock of NaNO3.

    [Edited on 5-11-20 by woelen]

    Fyndium - 27-8-2021 at 16:11

    It looks to me as a suitable method as conc H3PO4 is readily available. The yields did not seem to be great looking at some YT videos, but other source states it needs 300C to run.

    Using sacrificial flasks would be advisable as phosphoric acid apparently corrodes glass a little.

    Does H3PO4 have any dehydrating properties? Could it be used to distill above azeo HNO3?

    karolus28 - 28-8-2021 at 12:08

    Quote: Originally posted by Fyndium  

    Does H3PO4 have any dehydrating properties?


    afaik no, but (HPO3)n does, there's a thread on that from like 2008, basically you boil it in a copper crucible till it's kinda like glass or something like that.

    https://www.sciencemadness.org/whisper/viewthread.php?tid=44...

    Fyndium - 29-8-2021 at 04:15

    A further thinking.. I have a feedstock of KNO3 that has an impurity of water soluble phosphate. While being in benign amounts not effecting yields to a significant degree, shouldn't it upon addition of H2SO4 form phosphoric acid, which further reacts with the nitrate to form HNO3 and the corresponding phosphate, resulting in negligible losses?

    What I was also thinking if there is an impurity of KCl with nitrate, should the formed HCl be distilled over with HNO3, or react with the nitrate?