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ManyInterests
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Diluting 90+% Nitric Acid to 70%?
I've been looking at various ways of preparing nitric acid, and from what I've seen it appears to be a lot easier to make fuming nitric acid than it
is to make 65-70%. Largely because it has multiple steps you need to follow to get the more dilute kind.
So this got me thinking... is it possible to just dilute fuming HNO3 to 70% instead of making 65-70% from the start? I know it sounds like a dumb
question. But I'd rather ask dumb questions than make dumb mistakes.
I do know it is a very exothermic reaction and I would need to do it slowly.
[Edited on 20-10-2021 by ManyInterests]
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woelen
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Just distill nitric acid from sulfuric acid and a nitrate salt, to which a little water is added beforehand. The water will distill over with the acid
(azeotrope) and you'll get more dilute acid. Do not add too much water, it always is easier to dilute afterwards, than having to concentrate
afterwards.
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Tsjerk
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Doing what woelen suggests is easier than making concentrated acid from the same salt and sulfuric acid. You will have a more liquid mixture in your
flask with a lower temperature and less NO2. You can calculate how much water you would need for the azeotrope and take, let's say, 70% of that
amount.
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ManyInterests
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I've seen people use water, dirty sulfuric acid (drain opener grade) and a nitrate salt. But I've also seen them use pure sulfuric acid. I have plenty
of cleaned up sulfuric acid and would rather use that than my remaining drain opener grade.
So it's like cody's lab and nile red, but just less water added? That sounds simple enough. I'll need to make some and test its percentage. Looking at
them making a distillation for hours then having to distill again and monitor very closely what comes out and having to replace the receiving
container is a hassle. This is also a safety concern for me as I don't have a fume hood. I perform all these things in my balcony outside. No gasses
get in while it's closed, but the way the ventillation works in my apartment is that the moment I open my balcony door they're going to enter my place
like a vacuum which is a scary aspect when dealing with nitrogen dioxide.
| Quote: | | Doing what woelen suggests is easier than making concentrated acid from the same salt and sulfuric acid. You will have a more liquid mixture in your
flask with a lower temperature and less NO2. You can calculate how much water you would need for the azeotrope and take, let's say, 70% of that
amount. |
I don't know the exact quantities, but I guess that is the spirit of experimentation.
So let's recap to see if I've understood it. Add the nitrate salt and chilled sulfuric acid (say 404 grams and 240 ml respectively), but instead of
around 200 ml of water, I put in around 100 ml? I am using Nile Red's measurements. He used drain opener sulfuric acid which already has more water in
it.
[Edited on 20-10-2021 by ManyInterests]
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Sulaiman
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There are many threads on the production of nitric acid here on SM,
I would use sodium or potassium nitrate with a little excess sulphuric acid to distill off RFNA at atmospheric pressure.
There are various methods used to eliminate the dissolved NO2 (here on SM)
I can't think of a reaction where the dissolved NO2 is a problem.
For dilute or concentrated nitric acid without distillation I would use a very slight excess of sulfuric acid with calcium nitrate,
the calcium sulfate produced has very low solubility and can be filtered off,
giving a filtrate with a little calcium sulfate and sulfuric acid contamination,
but mostly nitric acid.
Distillation of dilute nitric acid at atmospheric pressure gives a more concentrated acid,
(at less than azeotropic concentration)
but does not produce significant NO2 contamination.
Dilution of nitric acid is exothermic,
but nowhere near as much heat is released compared to diluting sulfuric acid.
Chilling is good but not required.
CAUTION : Hobby Chemist, not Professional or even Amateur
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ManyInterests
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Thank you. I did look up some of the threads before I started this thread. But I think I got all the information I need for now. I hope to make my
first batch of HNO3 next week. Right now it's all about getting the water pump properly connected to the water jacket. I have a tube that fits the
pump, but is oversized for the water intake. I don't have any adapters, but if I glue the hose around the water intake it will still flow through the
jacket just fine.
| Quote: | For dilute or concentrated nitric acid without distillation I would use a very slight excess of sulfuric acid with calcium nitrate,
the calcium sulfate produced has very low solubility and can be filtered off,
giving a filtrate with a little calcium sulfate and sulfuric acid contamination, |
That would be an interesting experiment, but I have no calcium nitrate to try it out. The only nitrate salt I have is potassium nitrate. Right now I
decided to pull out my supply and grind it to a fine powder and I am putting it in the oven at around 70 Celsius to completely dry it out before
returning to the container.
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teodor
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Storing 90%+ (e.g. 98%) nitric acid is not easy. I use a Duran Protect bottle with a red Teflon-lined cap but the acid ooze through the cap dissolving
the protecting plastic from the outer side of the bottle. This is probably because night/day temperature changes and the ability of the acid to
evaporate and condensate at the cap. So, I think it is not the best concentration to stock the acid.
I never had a problem storing 50% HNO3. But azeotrope concentration is already very peculiar and can decompose when the bottle is exposed to light,
also it evaporates slowly even through the ground glass stopper.
So, if you don't need a concentrated acid (like in the case of just making nitrates and other general chemistry) I would recommend storing the main
part as a 50-55% water solution.
But I am also interested to know how people store their highly concentrated HNO3. I know there are some special bottle but I never saw them close.
[Edited on 21-10-2021 by teodor]
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Fantasma4500
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if you decide to go for distilling conc. HNO3 you can just DCM it, extract it like that.
then distill off the DCM at 40*C
should prevent nitric acid from decomposing, then dilute down accordingly
one person i spoke to made WFNA by Ba(NO3)2 and using some very small pore vacuum filtration glass cup which didnt allow the barium sulfate to pass
through
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Herr Haber
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Quote: Originally posted by teodor  |
But I am also interested to know how people store their highly concentrated HNO3. I know there are some special bottle but I never saw them close.
[Edited on 21-10-2021 by teodor] |
I use Duran bottles aswell but not the protected ones. I would be very annoyed to have one damaged by acid !
First, I'd remove the pouring ring. It only helps pressure escape and the gasses then attack the cap.
I ruined 1 cap with a pouring ring that still had a barb from molding then removed all pouring rings. No more problems.
I tried the other more expensive caps from Schott. They are better but not by much. They dont get attacked but they still leak enough vapours to
discolor labels and such.
I havent felt the need to use the ones with an inner conical seal to store nitric acid.
They would probably be better but my conclusion was that it was simpler to make the acid when needed rather than store something like that for more
than a couple of weeks.
[Edited on 21-10-2021 by Herr Haber]
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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Tsjerk
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I tried DCM extraction of KNO3/sulfuric acid, it works and the product is colorless anhydrous HNO3, but it isn't very efficient. The salt slurry is
very polar and is hard to extract with DCM. If your reagents are valuable to you, you could try to capture the DCM for repeated extraction.
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ManyInterests
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| Quote: Originally posted by teodor | Storing 90%+ (e.g. 98%) nitric acid is not easy. I use a Duran Protect bottle with a red Teflon-lined cap but the acid ooze through the cap dissolving
the protecting plastic from the outer side of the bottle. This is probably because night/day temperature changes and the ability of the acid to
evaporate and condensate at the cap. So, I think it is not the best concentration to stock the acid.
I never had a problem storing 50% HNO3. But azeotrope concentration is already very peculiar and can decompose when the bottle is exposed to light,
also it evaporates slowly even through the ground glass stopper.
So, if you don't need a concentrated acid (like in the case of just making nitrates and other general chemistry) I would recommend storing the main
part as a 50-55% water solution.
But I am also interested to know how people store their highly concentrated HNO3. I know there are some special bottle but I never saw them close.
[Edited on 21-10-2021 by teodor] |
I ordered several amber reagent bottles last summer. But none of them arrived. I realized I needed to improvise. I held onto a single empty bottle of
triple sec. It has a completely plastic cap and is amber in color.
https://www.lcbo.com/content/dam/lcbo/products/088328.jpg/jc...
I also have another glass bottle with a plastic cap that I've wrapped completely in red electrical tape in order to stop any light from coming in.
I know it's really not good for long-term storage. But here's the thing. I don't plan on storing HNO3 of any concentration for any long period of
time. Once I have some HNO3 that I need (either 68% or the 99%) I will use it as quickly as I can. Especially the WFNA. That stuff is deadly and
seeing how it set nitrile gloves on fire so quickly makes me very afraid of keeping it for a while. I need it to make some energetics, and I will get
my setup ready to make those the moment I obtain the nitric acid I need.
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ManyInterests
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I found this very fascinating thread that basically answers almost all my questions.
http://www.sciencemadness.org/talk/viewthread.php?tid=13090
The only difference between my setup is that I don't have a Clairsen adapter. But that shouldn't pose that much of a problem.
What I am concerned with is that he used pottery grade KNO3, while I am using homemade KNO3 extracted from Calcium ammonium nitrate cold packs. Also
he uses drain opener H2SO4, while mine is cleaned up and probably a touch more pure. Does that mean I just need to add a little more distilled water
to my flask?
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SWIM
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Good old Magpie.
He's a fine source. Really methodical and he would research everything first.
I think a few ml extra water would be a good idea if your acid is over 96%, but probably not critical.
If you add too much there will be some lower strength tailings at the end of the distillation, but foaming won't be as much of a problem and yield
will still be pretty good unless you really overdo it.
edit: Its probably not a matter of how clean the acid is, but how strong. The dark impurities in industrial grade acid don't seem to have much of an
inhibitory effect on the reaction.
[Edited on 29-10-2021 by SWIM]
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ManyInterests
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OK so I just want to give my report and documentation of my first attempt at making Nitric acid.
Firstly I am proud to say that my safety setup was top notch. Exactly no gasses made could have harmed anyone. They were fully contained.
Since safety is all good... my result wasn't. I did not need a clairsen adapter because I was using a 1000ml double necked boiling flask. I used
Magpie's recommended quantities and the foaming + resultant salt cake never got close to leaving my flask. The problem is that breaking up the salt
cake was a major pain and I needed a lot of water and sodium carbonate in order to dissolve it and neutralize any bisulfates before I poured the
remains down the drain.
The problem was that my nitric acid is really, really weak. Using this chart I probably got a concentration of 19.5 to 21% at the most.
https://www.handymath.com/cgi-bin/nitrictble2.cgi?submit=Ent...
I am really not sure what happened. But as I saw that the flask was going to dry up. What I did was lift the flask out of the heating mantle to
prevent any cracking, I think I might have accidentally poured the water that was condensing in my allihn condenser. That might have been the biggest
problem.
I will make my first attempt at fractional distillation to see if I can get my weak solution up to 68-70%. But in all honesty I would like if I just
got my desired strength the first time around... easier that way. Or make it stronger than necessary and just dilute it, which is what I was
originally asking about.
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Oxy
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| Quote: Originally posted by Antiswat | if you decide to go for distilling conc. HNO3 you can just DCM it, extract it like that.
then distill off the DCM at 40*C
should prevent nitric acid from decomposing, then dilute down accordingly
one person i spoke to made WFNA by Ba(NO3)2 and using some very small pore vacuum filtration glass cup which didnt allow the barium sulfate to pass
through |
According to MSDS (https://www.carlroth.com/medias/SDB-8424-IE-EN.pdf?context=b...) HNO3/DCM is potentially explosive mixture. IIRC someone on the forum also warned
about it, I don't remember if he actually experienced the explosion.
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ManyInterests
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Well I have no DCM and I won't be using it if there is any explosion hazard (which is also why I will not be making azeotropic hydrazine for my NHN. I
refuse to take any chances. I will freebase my hydrazine sulfate with sodium hydroxide and ethanol and use the solution I get from there for that
purpose).
I wanted to give another updated on my fractional distillation. It was my first ever fractional and I am mildly confused if I was doing this right.
So what I got pretty much all the time was water with a slight nitric acid touch. I decided not to keep them and neutralize them instead. What was
left in my boiling flask after almost an hour of that was a much stronger nitric acid than I had previously, but it was around 40%. I know it's
blasphemy to do this, but I also neutralized it since I did want to try to purify it further later. What was left was too little anyway.
It was my first fractional distillation and my first distillation ever. Pretty exciting! But for the next time, I'll follow Magpie's instructions
again, except I will use 10ml more sulfuric acid (I am confident I have at least 96%) and use far less water. Like around 10ml. So 110ml of acid to
10ml of water. The acid isn't the problem. Getting sulfuric acid is easy where I live and I have plenty of concentrated hydrogen peroxide to purify
it. But the nitrate salt is a pain and much more expensive for me to get.
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ManyInterests
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My god I feel so embarassed... also NileRed lied to me! Now I know exactly why my previous nitric acid synthesis went awry.
What happened is actually as simple as it is stupid. At the end of my original synthesis I had 100 ml of product in my flask but as I tried to raise
my flask from the mantle I heard an audible 'glug glug glug'. I then noticed that my 100ml was now around 250ml of something. I wasn't sure what
happened. I thought there was some water stuck in the alihn consender, but that made no sense.
Something like this happened again, and I know exactly what happened... The sodium hydroxide trap I setup (like in NileRed's video) actually sucked
the hydroxide solution into my flask of nitric acid. It's actually amazing I had any left at all. Or if there was any left.
Next time I will do what Magpie showed and just have a tube. Or not even. My fan will take care of the fumes. God I feel stupid. 450 grams and 200ml
of KNO3 and H2SO4 lost for nothing.
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ManyInterests
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Well that solved a major problem. Following Magpie's instructions. I only added 20ml of water instead of his 48ml. Final yield is less than 100ml of
acid, at around a concentration of 59 or 60%. I'll do a fractional distillation and hopefully get it to 68 or 70%.
Next time I try it I'll add less water. That should do the trick.
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Tsjerk
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| Quote: Originally posted by ManyInterests |
Something like this happened again, and I know exactly what happened... The sodium hydroxide trap I setup (like in NileRed's video) actually sucked
the hydroxide solution into my flask of nitric acid. |
What video?
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ManyInterests
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This one: https://youtu.be/KBeo8nww21g
Now his funnel was floating atop the sodium hydroxide solution while mine was at the bottom. The first time I did it I put 250ml of sodium hydroxide
solution in a 1000ml beaker. It still sucked up a lot of the solution at some moment. I am not sure why.
I decided to omit the trap all together, like what Magpie did in his article and doug's lab did in his video on making nitric acid.
I think my reduced yield had something to do with me omitting to grease the joints, which caused some acid gas to leak out. Another problem is while
cleaning my joint, I accidentally snapped part of the dripper (I don't know what that part is called. But it looks like the lower part of a glass
funnel). It still drips the acid into my flask just fine, but I am sure something is not working as optimally as previously.
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ManyInterests
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My attempts to concentrate my dilute batch either went almost right or did nothing. I was just one gram away from the correct concentration... and it
was a much higher heat.
I had a concentration of 1.3595 using that chart (27.19 grams to 20ml). Next time I will add a 10ml excess of sulfuric acid (just in case it isn't
strong enough) and only 5ml of water. I want this attempt to succeed. Better to dilute than to concentrate, which I am clearly having problems with.
[Edited on 8-11-2021 by ManyInterests]
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Oxy
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| Quote: Originally posted by ManyInterests |
Something like this happened again, and I know exactly what happened... The sodium hydroxide trap I setup (like in NileRed's video) actually sucked
the hydroxide solution into my flask of nitric acid. |
Be careful with that. Wrong setup of the trap and suck back may lead to explosion, serious injury, damage, poisoning or even death.
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ManyInterests
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| Quote: Originally posted by Oxy | | Quote: Originally posted by ManyInterests |
Something like this happened again, and I know exactly what happened... The sodium hydroxide trap I setup (like in NileRed's video) actually sucked
the hydroxide solution into my flask of nitric acid. |
Be careful with that. Wrong setup of the trap and suck back may lead to explosion, serious injury, damage, poisoning or even death.
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Yes! I am extremely lucky that the only thing that happened is that my final product was ruined and nothing else. I am not using a hydroxide trap
anymore.
I've decided to only make my distillations at night since I don't want any sunlight damaging my nitric acid. Also one thing I am noticing that no
matter how little water I add. I am always getting a far too dilute solution. I haven't done my latest attempt with 105/110ml of sulfuric acid + 5 or
6ml of water yet, but I am thinking about what else may have gone wrong.
I know that when making fuming nitric acid, your temperature must not go above 85 or 90 degrees Celsius. But what about lower concentrations? I've
seen the videos and even Magpie's article doesn't mention a number on the temperature.
I saw in Doug's lab that the temperature went up to 116 or 120 degrees Celsius, so that's what I turned my mantle up to. Is this excessive for the
azeotrope? Or do I just set the temperature to 85 like for fuming?
Also do I need to cover my glass in aluminum foil if I am making it during the night with no sunlight (I do use my flashlight to illuminate it,
otherwise it's too dark to see what's happening) or is that not necessary? Is it any light that causes degradation or is the UV rays from sunlight?
And I kinda feel dumb to ask this again. But is it possible WFNA down to 70% or will that cause problems? All I got was that it would be an exothermic
reaction, which I understand, but will the addition of water not work exactly or what?
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woelen
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No need to do the distillation in darkness. Full bright sunlight may cause some decomposition, but I think that heating the acid causes much more
decomposition than the sunlight. If you do the synthesis at the right time, you could do it somewhere in the shadow of a tree or building just to
avoid direct sunlight.
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ManyInterests
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| Quote: Originally posted by woelen | | No need to do the distillation in darkness. Full bright sunlight may cause some decomposition, but I think that heating the acid causes much more
decomposition than the sunlight. If you do the synthesis at the right time, you could do it somewhere in the shadow of a tree or building just to
avoid direct sunlight. |
Thanks for the advice on the sunlight. I guess one of the other reasons why my concentration was so low (albeit I got so close last time) was due to
the high heat. What is the better heat level for this? would putting it at 85 degrees Celsius work as well to make RFNA or 68% as it does for WFNA?
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