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Gammatron
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Failed distillation of HNO3 from KNO3 ??
So this morning I attempted a distillation of HNO3 using 550g of KNO3 and 300ml of rooto H2SO4 in a 1000ml rbf. I mixed them together last night so I
could be ready to run the reaction in the morning but as soon as I started heating the mixture it foamed up to the neck of the flask. I pushed it back
down with a stir rod and continued heating and melted down into a liquid as usual except I never got any NO2 fumes, just thick pale yellow fumes and
all the glassware that was in contact with it fumed profusely, looked like wfna except it has no reaction with copper even after diluting with water.
I didnt get a steady flow of distillate until 180C and it topped at 210C at the still head before I finally quit. The distillate does not fume at all
and has no smell, ph paper shows high acidity and it only reacts with Al foil after some delay.
I also checked my KNO3 with some sugar and it burned as expected with little leftover residue and I also know my H2SO4 is of good quality, so wtf is
going on?
[Edited on 3-23-2023 by Gammatron]
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clearly_not_atara
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Pale yellow fumes? Sounds like your KNO3 is contaminated with KCl.
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Gammatron
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KCl has an immediate reaction with H2SO4 at room temp producing a lot of bubbles. There was no perceivable reaction when I combined the acid and KNO3
and I stoppered the flask to keep it from absorbing moisture over night and there was no pressure release when I opened it in the morning.
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ave369
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What's the source of your KNO3? Are you sure it's KNO3 and not, for example, NH4NO3? NH4NO3 can decompose on heating and produce a lot of useless
outgassing and no HNO3 at all, and your distillate would be a weak solution of H2SO4 in that case.
To check it, try to dissolve your nitrate in water. If it is very very soluble, as in hundreds of grams per 100 ml, and cools significantly when
dissolving, it is definitely NH4NO3.
[Edited on 22-3-2023 by ave369]
Smells like ammonia....
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Gammatron
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I believe this particular batch came from a fireworks supply store but I also have a bunch that I bought on eBay, not sure which exactly i was using.
I'm at work now so I will have to check it when I get back home. It did appear that most of the fumes I made were of SO2 so seems like I was just
decomposing the sulfuric acid, especially at those high temps.
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ave369
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Well, if my guess is correct, there could be some H2SO4 oxidizing the ammonium and getting reduced, it's not impossible. H2SO4 also tends to decompose
a bit when it is distilled, especially together with some sort of reducer.
[Edited on 22-3-2023 by ave369]
Smells like ammonia....
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UC235
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Ammonium nitrate is much easier to use for making nitric acid because the ammonium bisulfate melts instead of being a horrible slushy foaming
crystalline mess. All of my nitric acid has been made from NH4NO3. Your ratios are all fucked up though. You've got 5.5mol of KNO3 and maybe 2.85mol
of sulfuric acid. The second proton on the sulfuric is useless, you should be using at least equimolar quantities, preferably excess sulfuric to
ensure the distillate is fairly dried and the reaction mixture remains slushy.
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Gammatron
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Honestly I didn't even check the ratio. I just had that in my notes that I copied from an old nile red video and it worked pretty well for him.
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Rainwater
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Quote: Originally posted by Gammatron  | | Honestly I didn't even check the ratio. I just had that in my notes that I copied from an old nile red video and it worked pretty well for him.
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Bad... bad madscientest.
You got to learn from the demonstrations not just copy them.
Here use this.
Attachment: Acid calculator.xlsx (10kB)
This file has been downloaded 235 times
Just fill in the orange squares with what you want and read the results.
It will tell you exactly the weights of reagents needed, assuming they are dry.
Their is even a tid bit at the bottom to make triations easier
Low heat and reduced pressure give the best yields.
My rig routinely gets +95% yields using extra water
"You can't do that" - challenge accepted
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Gammatron
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I know... I say this with shame "Honestly I didn't even check the ratio." Cause now I probably just wasted a bunch of valuable reagents, but maybe I
can save it by correcting the ratio and restarting?
Thanks for sharing that!
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B(a)P
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| Quote: Originally posted by UC235 | | Your ratios are all fucked up though. You've got 5.5mol of KNO3 and maybe 2.85mol of sulfuric acid. |
Really? Isn't 300 mL of (assuming concentrated) sulfuric acid about 5.5 moles? While I agree that an excess of sulfuric acid helps I consider the mass
of reagents used by the OP to be workable.
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Gammatron
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If I put a target of 250ml of 90% HNO3 into the calculator it gives me very close values to what I used so that rules out having the wrong ratio so I
guess I'm back to square one...
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Rainwater
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So was the 180c the hot plat temp, solution temp, or head temp?
[Edited on 23-3-2023 by Rainwater]
"You can't do that" - challenge accepted
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Gammatron
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Head temp. Meant to put that in the original post..
[Edited on 3-23-2023 by Gammatron]
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Rainwater
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The "target product volume" on line 9 is anhydrous product.
Line 18 "total volume of target" is how much distillate you can expect with 100% yield
Is your distillate water soluble?
[Edited on 23-3-2023 by Rainwater]
"You can't do that" - challenge accepted
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Gammatron
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I was just trying to find a target that gave a KNO3 value similar to what I used to see how much H2SO4 it called for.
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Rainwater
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The 180c is throwing me way off. It should have been 80~120c.
It couldnt have been ethylene glycol you would have blown up by now. It and nitrates are not nice together.
Do you have the msds on the acid source?
[Edited on 23-3-2023 by Rainwater]
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Gammatron
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It's a popular source among amatures. I've used it for other experiments and it works great.
I tried attaching a link to the pdf but it didn't work. It lists the only ingredient as H2SO4 93%, thought I think its actually closer to 96% iirc.
Rooto Drain Opener Sulfuric Acid MSDS
[Edited on 3-23-2023 by Gammatron]
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Rainwater
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The byproduct, was it a water soluble salt? One of the reagents has to be at fault.
[Edited on 23-3-2023 by Rainwater]
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Gammatron
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I will have to check it when I get home from work in a couple hours.
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Herr Haber
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KNO3 for fireworks is usually mixed with an anti-caking agent such as SiO2.
It shouldnt do much with the H2SO4 though and your temperature is very high so you should observe some NOx
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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Gammatron
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So the "KNO3" is barely soluable in water both before and after the reaction. I noticed the slurry gets quite hot when mixed with water and I think
its because it is full of unreacted H2SO4, I tried using it to make a nitration mixture for nitrocellulose before and all the cotton just dissolved
into the acid so its definitely not making any HNO3.
At the time that I purchased the KNO3 I also ordered a kg of KCLO4 and I fear that something got mixed up along the way. Either by the seller or when
I bottled them. That would explain the high temp distillate and why I got such a clean burn with sugar and the low solubility.. Ill have to do some
more tests in the morning, thats a little scary if I was distilling HClO4.. and im gonna be pissed if I wasted all my KClO4 ):<
[Edited on 3-23-2023 by Gammatron]
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Texium
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Yikes! I was wondering if that could have been what happened when I first read this. Fortunately you probably didn’t distill much perchloric acid,
since it is an even stronger acid than sulfuric, and boils at 203°C.
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ave369
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So it was KClO4 actually. This is an even more fabulous mixup than I thought.
| Quote: Originally posted by Texium | | Fortunately you probably didn’t distill much perchloric acid, since it is an even stronger acid than sulfuric, and boils at 203°C.
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From my experience, volatility matters more than acid strength, I've distilled HBr and HI using phosphoric acid which is significantly weaker than
both of them, but less volatile.
[Edited on 23-3-2023 by ave369]
Smells like ammonia....
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B(a)P
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| Quote: Originally posted by Gammatron |
At the time that I purchased the KNO3 I also ordered a kg of KCLO4 and I fear that something got mixed up along the way. Either by the seller or when
I bottled them. That would explain the high temp distillate and why I got such a clean burn with sugar and the low solubility.. Ill have to do some
more tests in the morning, thats a little scary if I was distilling HClO4.. and im gonna be pissed if I wasted all my KClO4 ):<
[Edited on 3-23-2023 by Gammatron] |
This definitely fits. When you heated the mixture any formed perchloric acid would have immediately decomposed yielding a lot of hydrogen chloride,
oxygen and chorine, the foaming you observed. The fuming on the glass is likely from hydrochloric acid. You probably distilled a mixture of water
hydrochloric acid and perchloric acid. How much did you end up with out of curiosity?
Edit
Just a thought - You should contact the seller, this was potentially a dangerous situation and as you say, you have likely wasted a very useful
reagent. I guess it depends how certain you are that the mistake was not yours.
[Edited on 23-3-2023 by B(a)P]
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