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Author: Subject: Nitric Acid from Sodium Bisulfite and nitrates
joseph6355
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[*] posted on 6-2-2018 at 07:22
Nitric Acid from Sodium Bisulfite and nitrates


I ran up into this video today made by the old Explosions&Fire channel (that now has been renamed) https://www.youtube.com/watch?v=VLOY-Jp2w1I
I was aware of this before the video, but I have a minor problem with obtaining sodium bisulfate.

This is the equation: 2NaHSO4 + 2KNO3 ==> 2HNO3 + Na2SO4 + K2SO4
Sodium Bisulfate is a PH decreaser, but it is almost impossible to find where I live. Instead, they use other substances as a PH decreaser, and those that are sold are liquids.
What I was able to find OTC is sodium bisulfite as a food preservative, and I was wondering if it would work: 2NaHSO3 + 2KNO3 ==> 2HNO3 + Na2SO3 + K2SO3

I could be wrong, but the hydroxyl group in the NaHSO3 molecule would deprotonate, and then form Sodium sulfite.
I'm not an expert in chemistry, but I think I thought it all out.
Sodium bisulfite is cheap and easily obtainable here.

Sorry if I made a mistake. Don't go hard on me. :P




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ninhydric1
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[*] posted on 6-2-2018 at 07:33


HSO3- isn't a strong enough acid to produce HNO3, so I doubt it will work. A weak acid can't produce a strong acid.



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joseph6355
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[*] posted on 6-2-2018 at 07:41


Quote: Originally posted by ninhydric1  
HSO3- isn't a strong enough acid to produce HNO3, so I doubt it will work. A weak acid can't produce a strong acid.

I didn't think about that...
It's unfortunate. :\

Edit: What would happen then, if I tried? The reaction wouldn't start at all?

[Edited on 6/2/18 by joseph6355]




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6-2-2018 at 07:43
ninhydric1
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[*] posted on 6-2-2018 at 07:47


Chances are you'll just have a solution of both.

Even if your reaction did work, the HNO3 would react with the sulfites to form SO2 gas and the corresponding nitrate salt.




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[*] posted on 6-2-2018 at 08:41


Quote: Originally posted by ninhydric1  
Chances are you'll just have a solution of both.

Even if your reaction did work, the HNO3 would react with the sulfites to form SO2 gas and the corresponding nitrate salt.

Good news. I managed to find Sodium Bisulfate.

Since this thread was moved to the beginners section...
The theoretical yield is 63 grams at a 100% concentration, but some of it would certainly decompose to NO2.
I have never tried this synthesis. Can someone tell me how much WFNA I would approximately get after distilling and removing the NO2 contamination from the acid, and also considering the acid that would be decomposed? 50 grams maybe?

Changing the subject a bit, is there a mask filter that would prevent the NO2 from getting into my lungs? I don't own a proper fume hood, and I'm also somewhat scared of NO2 after a synthesis of trinitrophenol that I did a couple of weeks ago.
I own a 3M 6200 mask btw.




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[*] posted on 6-2-2018 at 09:25


In place of:

2NaHSO4 + 2KNO3 ==> 2HNO3 + Na2SO4 + K2SO4

try preparing Mg(NO3)2 by mixing up a concentrated solution of MgSO4 (Epsom salt) with KNO3 from stump remover. Freeze till the K2SO4 formation is evident. Decant removing K2SO4, dilute and refreeze to obtain Mg(NO3)2•6H2O. Remove crystals, heat and collect vapors of dilute HNO3. Reactions:

MgSO4 + 2 KNO3 = Mg(NO3)2 + K2SO4

Mg(NO3)2 + 6 H2O = Mg(NO3)2•6H2O

Mg(NO3)2•6H2O --heat to over 130 C--> Mg(OH)NO3 + HNO3 + 5H2O

Per a source (https://chemiday.com/en/reaction/3-1-0-7303 ), to quote:

“The thermal decomposition of hexahydrate nitrate magnesium to produce magnesium hydroxide-nitrate, nitric acid and water. This reaction takes place at a temperature of over 130°C.”

Interestingly, Wikipedia presents an alternate path on the thermal decomposition of magnesium nitrate, likely not referring to the hydrate:

2 Mg(NO3)2 → 2 MgO + 4 NO2 + O2

Reference: see https://en.wikipedia.org/wiki/Magnesium_nitrate

Note, my personal experience, as reported on SM, extends to aqueous Mg(NO3)2 preparation, and once on evaporation upon standing in air, the creation of a very hygroscopic salt. As such, I doubt if there is an easy path to anhydrous magnesium nitrate, other than those involving NO2, so the Wikipedia path to NO2 appears circular in all likelihood.

[Edited on 6-2-2018 by AJKOER]
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[*] posted on 6-2-2018 at 09:38


I have done this a few times with potassium nitrate and calcium nitrate. Calcium nitrate works WAY better but requires very strong heating so if you do not have a strong enough burner all of it will not react. Also, use an excess of bisulfate to keep things liquid. It is not hard to clean out with hot water.

I got the calcium nitrate from dissolving ammonium calcium nitrate fertilizer in water, filtering it, and driving of the water and ammonium nitrate with lots of heat. Do the dehydration outside because the calcium nitrate will decompose slightly into annoying nitric oxide.
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[*] posted on 6-2-2018 at 11:01


I don’t think you can use bisulphate as the acid to generate nitric acid, because of the pKa values.

H2SO4 = -3
HSO4- = 1.99
HNO3 = -1.4

Relative to the nitric acid, bisulphate would be considered a weak acid. In conjunction, I have used the method to generate nitric acid in the past and the resulting crystals are highly acidic, indicating the equation H2SO4 + KNO3 -> KHSO4 + HNO3




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[*] posted on 6-2-2018 at 11:37


pkA is blablabla, equilibrium is the force you can use!

When I was a 8- or 9yrs old kid and had no access to hydrochloric acid for me hobby I've made HCl gas using NaCl+NaHSO4 milled with mortar+pestle and then heated strongly (open flame or very strong heatplate) to push equilibrium to make HCl and make 10% HCl from it :cool:

NaCl + NaHSO4 <<<---> HCl(g) + Na2SO4 etc.

I don't see why this wouldn't work with Nitrates as long as they are stable at high temps (don't use NH4NO3 etc.).

Though don't expect high yields! A few drops of sulfuric acid/battery acid can catalyze the reaction a bit, though I would recommend to find conc. H2SO4 or make conc. H2SO4 from battery acid and use that (much better yield!)

PS: Similar way you can obtain super strong acids like HBr, perchloric acid etc. from their salts + H2SO4 + heat even if H2SO4 is much weaker



[Edited on 6-2-2018 by EilOr]

[Edited on 6-2-2018 by EilOr]
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[*] posted on 6-2-2018 at 11:37


Quote: Originally posted by LearnedAmateur  
I don’t think you can use bisulphate as the acid to generate nitric acid, because of the pKa values.


https://www.youtube.com/watch?v=TtPiwbRA4N8

Apparently it's possible to do it if you distill off the nitric acid to drive the reaction forward. At any given moment there's only a tiny bit of HNO3 in the reaction flask, but as long as you keep removing it more will be produced.
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[*] posted on 6-2-2018 at 13:20


You can even do it in solution because calcium sulfate is insoluble but i would not recommend it.
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[*] posted on 6-2-2018 at 14:03


Ah, well I stand corrected, I’ve always made my acids from excess H2SO4 and been left with the bisulphate even when heating to distill - I guess I just wasn’t doing it for long enough and with too much H2SO4 for complete conversion.



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[*] posted on 6-2-2018 at 18:14


Quote: Originally posted by Reboot  
Quote: Originally posted by LearnedAmateur  
I don’t think you can use bisulphate as the acid to generate nitric acid, because of the pKa values.


https://www.youtube.com/watch?v=TtPiwbRA4N8

Apparently it's possible to do it if you distill off the nitric acid to drive the reaction forward. At any given moment there's only a tiny bit of HNO3 in the reaction flask, but as long as you keep removing it more will be produced.


Looking at this You Tube video, seems that what's produced in large quantities is nitrogen dioxide (NO2), while the water remains in the reaction flask. Just a tiny amount of nitric acid was produced at the end of distillation. That is, the nitric acid decomposes as soon as formed in H2O, NO2 and O2.

Thinking about that, it's look feasible react bisulfate and nitrate to afford nitric acid but, I'd rather follow another route, bubbling the nitrogen dioxide evolved from the reaction into a flask with hydrogen peroxyde:

2 NO2 + H2O2 --> 2 HNO3

instead of try to distill the fumes as in the You Tube video "myst32YT" did.

Concentrating the obtained acid is easy and have been already discussed at this forum in other threads.
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[*] posted on 7-2-2018 at 00:12


Quote: Originally posted by ninhydric1  
HSO3- isn't a strong enough acid to produce HNO3, so I doubt it will work. A weak acid can't produce a strong acid.


It's trickier than that. By Le Chatelier, a weak acid can produce a strong acid if the strong acid is removed fast enough and cannot react back. Usually this means that the strong acid is volatile and is distilled off, or it is unstable and decomposes, and the weak acid is neither unstable nor volatile. I've made hydroiodic acid from iodides and phosphoric acid, hydroiodic being a much stronger acid than phosphoric. There are reports of using boric (!) acid for similar purposes.

But in this case, sulfurous acid is much less stable than nitric, so it will not work. A redox side reaction is also very possible, given that nitric acid is a strong oxidizer and sulfites are reducing agents.

[Edited on 7-2-2018 by ave369]




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[*] posted on 7-2-2018 at 02:12


I have tread reacting the nitrogen dioxide but it seems not much is produced after the reaction has started.
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