Sciencemadness Discussion Board

golfpro's Nitric Acid for Beginners

golfpro - 13-7-2013 at 09:28

<strong>Silver Nitrate w/ H2SO4 and Nitrate salt</strong>

I know I had another thread like this that went sour before there was any useful info posted.

So, copper can be disolved in simply a 20% HCl solution w/ sodium nitrate. I am wondering if there is an alternative to silver nitrate for those without nitric acid or expensive distilling equipment. Here is a video: I know he talks like a goon, apparently he gets the sulfate to seperate from nitric acid and filters it out.

Can it be done to get reasonably pure silver nitrate?


[Edited on 13-7-2013 by golfpro]

<!-- bfesser_edit_tag -->[<a href="u2u.php?action=send&username=bfesser">bfesser</a>: given a generic subject]

[Edited on 24.8.13 by bfesser]

chemcam - 13-7-2013 at 09:42

That is just his inner nerd coming out haha. That member is now active here again, you can ask him. ScienceHideout

cyanureeves - 13-7-2013 at 09:52

i have done this method and it dissolved sterling fairly easy which i then separated the copper from silver by adding table salt and making silver chloride.that goon speaking IS but non other than Dr.Evil

golfpro - 13-7-2013 at 16:28

What do you mean separate the silver from the copper?? Where is there copper?

chemcam - 13-7-2013 at 16:50

Copper is in sterling silver. If you have silver bullion there won't be any copper except maybe <0.001% if its 99.999% pure like most bullion.

cyanureeves - 13-7-2013 at 18:23

sterling= 92.50%silver 7.50% copper unless its brittish sterling which has uuuh ,raaather, more silver!

golfpro - 16-7-2013 at 19:09

My silver is 99.7% pure

Ok so now here is a question:

I mix ammonium nitrate (pure) in sulfuric acid (93%) drain cleaner, not the purest stuff, and this disolves quite nicely, is there any way to precipitate ammonium sulfate here? That takes care of the sulfates and ammonium then I would be left with only concentrated nitric acid with some impurites (how much of a problem would this be when the silver nitrate recrystalizes at room temperature?), but could still disolve silver let's say (w/ heat) and I do the process for silver nitrate that calls for 70% nitric acid and then the evaporation.

weiming1998 - 16-7-2013 at 22:22

A mixture of sulfuric acid and a nitrate salt can dissolve silver, however pure silver nitrate cannot be obtained. Due to the contamination of sulfate ions in the mixture, silver sulfate will be produced (as it has a much lower solubility compared to the nitrate). There is no practical way of removing the sulfate impurity (apart from distillation).

With a different (and an excess of the) nitrate salt (like barium nitrate), and if the resulting sludge is filtered, sulfate ion contamination can be greatly reduced and this might actually produce silver nitrate, with a bit of silver lost as the sulfate. But with ammonium nitrate, it would be very hard to produce any silver nitrate at all.

golfpro - 17-7-2013 at 07:41

How about Sodium Nitrate as the nitrate salt?? I can make that but Barium nitrate is a bit expensive for the hazmat fees.

[Edited on 17-7-2013 by golfpro]

Nitric Acid concentration from distilling H2SO4/NO3

golfpro - 18-7-2013 at 18:39

Hi, I am wondering what exactly or approximately is the concentration of nitric acid that is distilled from a mix of (93% roughly) sulfuric acid and ammonium nitrate (pure). I only have access to a retort for distilling anything which is basically just a one peice distilling appuratus, a round bulb flask with a narrow neck and condenser, not fancy at all.

Is this 70% acid?? There is no vacuum here. How is 100% Nitric acid attained?

I could do a titration, I would probably have to dilute the nitric x10 or something to avoid a violant reaction, problem is I do not have any indicator, I'd have to go off of bubbles.

[Edited on 19-7-2013 by golfpro]

subsecret - 18-7-2013 at 21:44

Nitric acid approaching 100% is probably hard to come by. The azeotrope of nitric acid and water is somewhere between 60 and 70%.


With good dehydrating agent, like H2SO4.

If you chose to use sulfuric acid, be careful as this mixture would be EXTREMELY corrosive. I'm not sure how much you could increase the concentration by distilling over H2SO4.

If possible, start with dry reagents. Don't dry ammonium nitrate with heat, as it becomes unstable and may combust or explode. As always, do research before experimenting to prevent accidents. (I'm not sure if mixing anhydrous nitrates with H2SO4 is dangerous).

Also, do this distillation in a fume hood or outside, especially because you are using only a retort. I recommend putting the end of the retort in a round-bottom flask or Erlenmeyer flask in an ice bath to catch all of the acid vapors. I would also recommend distilling rather slowly.

As for the titration, pH indicators containing phenolpthalein are not terribly expensive for how far they go. For a titration, you might only use 1-2 drops. If this still isn't a feasible option, you can make a pH indicator out of red cabbage. Sadly, this indicator does not change color immediately past a certain point. The color changes are smoother, so you'd have to be very careful not to overshoot.

As always, do preliminary research to prevent accidents. Be safe.
Hope this helps.

[Edited on 19-7-2013 by Awesomeness]

Pulverulescent - 19-7-2013 at 02:20

How is 100% Nitric acid attained?

N2O5 is dissolved in azeotropic HNO3 to bring the conc. to 100%!
And NO2 can be reacted with water under pressure to obtain near-anhydrous acid.
But by distillation, the highest conc. is obtained from KNO3/H2SO4 mixtures!
Some NH4+ is oxidised by hot, concentrated H2SO4 during distillation, diluting the acid produced.

Fantasma4500 - 19-7-2013 at 08:27

well 93% then you have say...
using a 100 mL 93% H2SO4 and 50g KNO3
that means you have 7g H2O
not actually sure where the water goes, but of what i know H2SO4 would be more craving for the water than the HNO3, thereby i would say approx 99% depending on how much 'air' you let get in contact with the destillate, as the azeotropic HNO3 (in which starts at 70% by my knowledge) will be anhydrous and hygroscopic

by my experience you really do need vacuum otherwise you might want the tube leading away to be very very low, pretty much few millimetres above the liquid (in where HNO3 vapour cannot be)
HNO3 is a pretty heavy vapour, so if theres far up to the tube leading away chances are very high that you will only get NO2 over
vacuum otherwise fill the retort as much as possible

always wanted a retort really, be happy with it, and keep in mind that aluminium will not react with HNO3, but only slowly with NO2
if you want the HNO3 for nitrations, 70% HNO3 is pretty well all round concentration

anyhow, if you have 7g water in total, or 7 mL then by any means you would maximum in the perfect world have 7g water total in your destillate

weiming1998 - 19-7-2013 at 08:50

With an excess of sulfuric acid, (almost) water-free nitric acid can be made (See However, nitric acid made and distilled without a vacuum will always contain a significant amount of nitrogen oxides dissolved in it. Thus, white fuming nitric acid (anhydrous nitric acid containing very small amounts of dissolved nitrogen oxides) can only be produced by vacuum distillation.

It is important not to crank the heat up too much during distillation, as more nitric acid will decompose, producing nitrogen dioxide and water, which dilutes down your product.

Fantasma4500 - 19-7-2013 at 09:23

i think what you want to do, as this is something related to your 99% HNO3 destillation thread, you want to DILUTE your H2SO4 and then react it with a nitrate
this is much easier than destilling high conc. HNO3 and thereafter diluting it
i would say per 100 mL 93% H2SO4 you add 23 mL/g H2O
then you SHOULD have 123 mL 70% H2SO4, althought this sounds wrong to me
anyhow; dilute the HNO3 before destillation, get the HNO3 (aluminium tubing is suitable for this destillation)
thereafter react with silver
when you react it like this you might want to be careful as NO2 is evolved and you cant avoid this
put a beaker with NH4OH aside the beaker with Ag + HNO3
if it doesnt start up gently heat the HNO3

i suppose what you want to do with the finished AgNO3 would be to precipitate a double salt, am i right?

golfpro - 19-7-2013 at 13:56

I want to precipitate a clean pure double salt. I want to collect pure AgNO3, and then use some nitric acid so I have a solution of dilute nitric acid (don't know how dilute just yet) with disolved silver nitrate, I bubble acetylene gas through this solution to precipitate a double salt silver acetylide. Is it correct that the silver nitrate needs to be in nitric acid in order for the double salt? Because I have no use for pure AgC2.

golfpro - 19-7-2013 at 14:31

What I gather:

-Around 85-99% nitric acid may be made by nonvacuum distilling sulfuric/ammonium nitrate mix with slight excesss sulfuric acid, this is slightly contaminated with nitrogen dioxide and a yellowish color, (but can not be used for RDX)

My heat source for distillation will be a salty water bath heated by a flame torch, I could probably get around 110*C, or get an oil bath if need be.

I think getting 70% nitric acid by diluting the sulfuric a bit before hand would really be taking shots in the dark for the concentration.

Antiswat, what is a good procedure for the double salt AgC2*AgNO3?

Dornier 335A - 19-7-2013 at 15:03

Nitric acid is produced in the reaction. Pure Ag2C2 is only produced in a basic solution.

PeeWee2000 - 19-7-2013 at 16:10

You could also get an appropriately graduated hydrometer and measure the specific gravity of the solution and compare it to this convenient chart This method seems fairly straight forward and cheap to me if you dont mind waiting a couple days after ordering one or possibly you might find one at your local hardware, as I know they are used in measuring the % Concentration of alcohol commonly but it is probably not in the right density range to measure nitric acid. There are also other hydrometers commercially available such as a battery acid hydrometer which might be in the right range, but youre better off getting a hydrometer specifically made for what it is youre looking to measure.
From my personal experience when using a vacuum to synthesize it from H2SO4 and NaNO3 it came out very clear and fumed, indicating 70%+ and worked fine for synthesizing Nitroglycerin.
What would you be using the nitric acid for anyways if you dont mind me asking golfpro?

[Edited on 20-7-2013 by PeeWee2000]

golfpro - 19-7-2013 at 17:05

I have a couple uses for nitric acid right off the top of my head, well it's cool first of all, secondly, to make silver nitrate, to make the double salt silver acetylide, and possible RDX, I just use a nitrate salt for ETN or any Nitric ester, no sense in the expensive, tedious to make nitric acid when nitrate salts give almost just as good yields.

BTW, I'd put any amount of ammonium nitrate in any oven, any temperature (reasonable) all day every day until the cows come home without an ounce of worry in my mind.

Like I said, I don't have fancy vacuum equipment, only a retort.

[Edited on 20-7-2013 by golfpro]

[Edited on 20-7-2013 by golfpro]

Oscilllator - 20-7-2013 at 02:21

Quote: Originally posted by weiming1998  
With an excess of sulfuric acid, (almost) water-free nitric acid can be made (See However, nitric acid made and distilled without a vacuum will always contain a significant amount of nitrogen oxides dissolved in it. Thus, white fuming nitric acid (anhydrous nitric acid containing very small amounts of dissolved nitrogen oxides) can only be produced by vacuum distillation.

It is important not to crank the heat up too much during distillation, as more nitric acid will decompose, producing nitrogen dioxide and water, which dilutes down your product.

I have actually observed results that contradict this. If I carry out the distillation at lower temperatures, then NO2 is very visible, but if it is carried out at higher temperatures there is barely any NO2 contamination. I have previously made a thread on this , but I don't recall receiving a satisfactory explanation fo this phenomena.
The distillation was done with KNO3 and clear drain cleaner labelled as 98% H2SO4. The acid obtained was yellow and formed a passivation layer with copper, indicating it is very concentrated. I have yet to do a titration on the acid, but its on my to-do list :).

The picture that on the right is a picture that was taken early on in the reaction, before it got going. The other one is from about 10 minutes later and as you can see there is minimal NO2 contamination.
IMG_20130714_132245.jpg - 214kB IMG_20130714_131634.jpg - 233kB

[Edited on 20-7-2013 by Oscilllator]

Pulverulescent - 20-7-2013 at 03:17

I have actually observed results that contradict this. If I carry out the distillation at lower temperatures, then NO2 is very visible, but if it is carried out at higher temperatures there is barely any NO2 contamination.

This is because NO2 is swept from the flask, on forming, by increased HNO3 vapour production!

weiming1998 - 20-7-2013 at 04:47

Wikipedia states that NO2 decomposes to NO and O2 (both colourless) at 150 degrees Celsius ( Maybe that is why there is appears to be no NO2 in the flask.

Fantasma4500 - 20-7-2013 at 07:03

he wanted the double salt
so lets see...
if you use HCl or H2SO4 it will be impossible as the AgNO3 will precipitate in SO4 or Cl salt
you want to distill some HNO3 for this
thereafter you dont need to dry it
just lead the C2H2 through the solution, a small amount of HNO3 is added to the AgNO3 to get a good double salt, instead of having non-double salt impurities in it
the finished double-salt bangs very very loudly, dont use too much inside

Fantasma4500 - 20-7-2013 at 07:06

view your other thread, also on a sidenot: use a tube thats very thin, then you will get smaller C2H2 bubbles and then you will need less gas to react it
perhaps make tiny holes in the bottom of the hose, and stopper the end so you get a stream of micro bubbles?
finished product also needs to be absolutely dry before it will do anything interesting; store away from light / UV, speeds decomposition up alot

golfpro - 20-7-2013 at 10:50

So is it even less desirable to have NO contamination than NO2? what temp should my oil bath be?

Pulverulescent - 20-7-2013 at 11:58

NO is a product of nitrogen oxidation and is further oxidised to the red NO2 form by contact with oxygen.
Oil-bath temps shouldn't go much above 121°C as this is the azeotrope's max boiling temp..

golfpro - 20-7-2013 at 12:31

Somehow I had in my mind that nitric acid distilled from a sulfuric mix get's an acid that is higher than the 70% azeotrope because the sulfuric can dehydrate the nitric a bit.

I really wish I had some of that liquid acid-base indicator, use a few drops and it turns purple once it hits a basic solution, I could easily titrate the nitric acid and know the exact concentration. Distilling from a retort with nitrate salt and sulfuric, some people here have said gives 50%, and others said gives closer to 85%-92%.

bfesser - 20-7-2013 at 13:28

<a href="" target="_blank">Phenolphthalein</a> <img src="../scipics/_wiki.png" /> solution?

[Edited on 7/20/13 by bfesser]

golfpro - 20-7-2013 at 13:36


Oscilllator - 20-7-2013 at 21:03

Pulverulescent I'm afraid your idea doesn't hold up. If the red NO2 was being swept away by increased HNO3 vapors, then surely once the HNO3 had been condensed then the red NO2 would re-appear. This is not what happened, almost no NO2 was observed coming from the vacuum take-off adaptor at the time when the flask was clear. But when the flask was filled with NO2 then NO2 vapor were observed coming out from the vacuum take-off.

weiming's explanation seems more likely to be correct, since I don't have a still head that a thermometer can be attached to, so I cant monitor the temp of the distillation. Since I was using a sand bath, it is entirely possible the temperature reached over 150C

And yes golfpro, HNO3 obtained by distillation can easily be over the azeotropic concentration, although I don't have any exact figures.

hissingnoise - 21-7-2013 at 01:10

I'm afraid your idea doesn't hold up. If the red NO2 was being swept away by increased HNO3 vapors, then surely once the HNO3 had been condensed then the red NO2 would re-appear.

Look, it's really quite simple; nitric acid decomposes on heating ─ NO2 will not dissociate because the vapour temp. in the flask won't normally reach 150°C!
Even if it did, it would reform on cooling . . .

But then again, you just may have spotted an anomaly that has eluded other scientists for these last few centuries?

Pulverulescent - 21-7-2013 at 01:16

Ooops! 'Used my alter ego by mistake . . .

Oscilllator - 21-7-2013 at 02:10

Quote: Originally posted by hissingnoise  
I'm afraid your idea doesn't hold up. If the red NO2 was being swept away by increased HNO3 vapors, then surely once the HNO3 had been condensed then the red NO2 would re-appear.

Look, it's really quite simple; nitric acid decomposes on heating ─ NO2 will not dissociate because the vapour temp. in the flask won't normally reach 150°C!
Even if it did, it would reform on cooling . . .

But then again, you just may have spotted an anomaly that has eluded other scientists for these last few centuries?

If the nitric acid is decomposing and the NO2 isn't dissociating, then why isn't there a visible red colour? You appear to be just contradicting me, and not offering an alternate view.

Pulverulescent - 21-7-2013 at 03:46

OK! Nitrogen dioxide exists in equilibrium with its colourless dimer; N2O4 ↔ NO2!
Heat shifts the equilibrium to the right, deepening the colour.
During distillation, hot, red NO2 fills the flask initially, but as ebullition increases this is largely displaced by HNO3 vapour.
The cooled vapour condenses, dissolving NO2 and lemon-coloured acid drips from the condenser!
A small quantity of NO2 escapes the condenser, depending on cooling-water temp. but the distillate contains most of the NO2 produced!

Oscilllator - 21-7-2013 at 23:13

OK! Phenomena explained! Nice use of excessive exclamation marks!

ElizabethGreene - 23-7-2013 at 14:29


Titration is the way to answer this question. If you don't have a pH indicator, get some red cabbage and make some. To make it, shred the cabbage and boil about a cup of it in two cups of water. After 10 minutes, drain it filter it with a food safe filter retaining both components. The solid component is delicious with salt and pepper. The liquid component is an effective pH indicator. Addition of 10% by volume of drugstore isopropyl alcohol will prevent it from going rancid.

Calibrate it using solutions of Vinegar (CH3COOH), HCl, NaOH, and NaHCO3.

Conveniently, the solutions of NaOH and HCl are what you need to titrate acids and bases respectively.


Nitric Acid from Retort.

golfpro - 25-7-2013 at 10:54


I distilled approx. 10ml nitric acid from 50ml sulfuric acid/38gram KNO3, I used an oil bath and heated up to about 140* C, it took about 15 minutes.

Well I had a gram peice of silver I added to 10ml Nitric Acid and no reaction at all, then I add my 10ml to hot oil bath, some nitrogen dioxide gas was made, but still the silver peice looks exactly the same, is my nitric not strong enough?.

My nitric acid is kind of yellowish from nitrogen dioxide contamination, but I did use a retort..


bfesser - 25-7-2013 at 11:01

You may need to dilute it slightly with water. Dissolution will be slow. Apply gentle heating. Be patient.

[Edited on 7/25/13 by bfesser]

annaandherdad - 25-7-2013 at 11:55

You will have to heat the HNO3 if you want an appreciable rate of reaction with a lump of silver. I found 70-80C was about right, using 20-30% HNO3. I would guess that more dilute acid will work fine, too, as long as it is heated. The reaction with silver is pretty slow at room temperature.

On the other hand, NHO3 reacts rapidly enough with silver powder or dust at ordinary temperatures, in my experience, in which I have used silver powder created by reduction of silver chloride in an alkaline solution of glucose.

There's a Nurdrage video on this.

woelen - 25-7-2013 at 12:12

I think that the acid is too concentrated. Some metals are passivated by highly concentrated acid. Try mixing the acid with half its volume of water and then add the silver.

You could also try adding other metals. Copper reacts violently with nitric acid, giving dense brown fumes. If the acid does not react with copper, then add half its volume of water and swirl. If it still does not react with copper, then it is no nitric acid or something which only contains a small amount of nitric acid.

golfpro - 25-7-2013 at 13:29

I got it, I had to use a good amount of heat though, actually some silver nitrate precipitated as crystals after the acid cooled.

kilowatt - 25-7-2013 at 18:51

I don't believe that the acid from a simple retort is much less concentrated than if you had used a full reflux column, especially if you did an anhydrous reaction. Even with a wet reaction, should be getting pretty close to azeotropic once the water is off.

I once dissolved a roughly 1oz lump of sterling silver in concentrated nitric acid at room temperature, before knowing that the dilute acid was more effective in that case. While the copper went into solution, silver nitrate slowly formed as white crystals over the course of about a year before the silver was gone. Definitely not a rapid process. I suppose the more readily dissolving copper it more difficult in that case, if pure silver dissolves relatively more readily.

[Edited on 26-7-2013 by kilowatt]

Storing concentrated Nitric Acid

golfpro - 26-7-2013 at 07:21


I have these dark brown glass bottles with black plastic lids, these are not acid bottled though and I was thinking I could store some nitric in this? I didn't know if the HNO3 vapours would attack the lid though, or if I might be better off trying to seal the top with aluminum?


bfesser - 26-7-2013 at 07:24

Does the inside of the cap have a transparent plastic cone? Your best off just finding a bottle with a PTFE-lined cap.
Also, storing nitric acid has been discussed to death. Please use the <img src="./images/xpblue/top_search.gif" /> <a href="search.php">Search</a> function.

[Edited on 7/26/13 by bfesser]

Mailinmypocket - 26-7-2013 at 08:07

I get all my bottles, vials etc from Qorpak. The green caps are PTFE lined and stand up to almost anything. They also have some Teflon lined septum vials, which also work nicely for nasties (provided you don't puncture them, obviously). I got some from Dr.Bob a while back and liked them so much I bought more from Qorpak :) Maybe check with him first as he might be able to give you a good deal on Teflon lined bottles.

Some examples:

image.jpg - 83kB

Fantasma4500 - 26-7-2013 at 08:23

you can as if you have it laying around by now take something coneshaped and cover in aluminium foil, then shove it carefully yet with power down the bottle opening, so that it will be completely sealed with aluminium

CaliusOptimus - 26-7-2013 at 11:06

Careful with that silver nitrate, it stains everything... and you won't know it until a week later!

golfpro - 26-7-2013 at 19:47

I have my nitric acid in a glass bottle with a glass stopper that doesn't quite fit, just a tad bit too big and infact if the acid is swirled, white fumes come out a bit. This is stored in the garage. I plan on using it/getting rid of it within a week probably.

During the whole process, I avoided fumes for the most part (you immediately feel it on your sinus) and all work was done outside however I had one kind of nasty inhalation of the fumes, I've heard of breathing the fumes can cause a serious medical emergency, but is this from prolonged exposure or will a few whiffs cause a serious problem?

golfpro - 19-8-2013 at 16:59

So the nitric acid from H2SO4/KNO3 in the correct ratio (I forgot which) even from a retort will be almost pure aside from NO2 contamination? Is there anyway to remove that?

Nitric Acid yeilds from Retort?

golfpro - 24-8-2013 at 06:07

Hey for those using retort, how much concentrated nitric acid are you getting per distillation with what amount of sulfuric and KNO3? I don't have a problem with the purity, but I use 250ml sulfuric acid and then the proper amount of KNO3 I forgot which, and then only get 50ml of Nitric acid??? Am I losing my acid in the way of it just not condensing and fuming off instead? I don't cool the tube on the retort but the acid drops into a ice cold beaker. I use an oil bath at least 150* C

my retort only holds 500ml, and I don't like 300ml sulfuric yeilding only 50ml Nitric... This is with the correct amount of KNO3.

subsecret - 24-8-2013 at 06:32

Try using a cold round-bottomed flask. This will provide a larger cold surface.

hissingnoise - 24-8-2013 at 06:48

I don't cool the tube on the retort but the acid drops into a ice cold beaker.

On distillation, the neck of the retort heats quickly until the glass reaches the vapour temperature and the vapour then largely escapes!
You could try pushing a cooled condenser onto the neck using teflon tape to minimise leaks . . .
Otherwise, just use small quantities of reactants ─ fiddly, but you'll lose less product!

cyanureeves - 24-8-2013 at 07:33

i got a 500ml retort and never used it because of that same thing but using less reactants is what i would do also.i even thought about attaching an aluminum tube to the neck and sticking out through a hole in my tool shed wall.i would probably have to only distill in the winter though and hope the aluminum passivates.

golfpro - 24-8-2013 at 13:10

The distillation would work much better in the winter, but is there any way to cool the neck like wrapping a baggy of crushed ice and water and taping it around the neck?

This would cause moitsture to condense on the neck and maybe even drip water into the beaker which is supposed to get high concentrated nitric acid and then defeat the purpose.

I bet I'd get at least twice the amount of acid distilling in 15*F weather compared to 85*F Until then I've got to find a way to cool the neck. Maybe a cloth dipped in ice cold water and wrap that around..

bfesser - 24-8-2013 at 15:01

<strong>golfpro</strong>, I'd appreciate it if you replied to your existing threads on very similar (or identical) topics, rather than starting new ones. I don't know how things are run in EM, but out here, your new topics are excessive.

[edit] I've merged three of your topics on nitric acid so far, and know there is at least one more. I recommend using the search function before posting, and posting replies in appropriate threads rather than starting new ones. <img src="../scipics/_warn.png" /> <em>If you open any more beginnings-level topics on nitric acid, I will likely lock or remove them.</em> <img src="../scipics/_warn.png" />

[2nd edit] Oh, to hell with it! I merged all five of them&mdash;I don't care if it's a little messy; this is low-level stuff.

[Edited on 25.8.13 by bfesser]

Kiwichemicali - 27-8-2013 at 10:22

Quote: Originally posted by Pulverulescent  

The cooled vapour condenses, dissolving NO2 and lemon-coloured acid drips from the condenser!
A small quantity of NO2 escapes the condenser, depending on cooling-water temp. but the distillate contains most of the NO2 produced!

The method I normally use to get rid of the NOx is bubbling dry air through the nitric acid while heating it to about 50 degrees C.
Would bubbling O3 do the job quicker? I'm considering building an O3-generator as a hobby project so if it is usable to eliminate the NOx that would be a nice application for it.


woelen - 28-8-2013 at 02:22

I hardly expect the O3 from a standard O3-generator to be of any influence. Of course, the O3 will oxidize the NO2 (in combination with water) to HNO3, but usual O3-generators only have a few tenths of percent at most of O3. The rest is air (or oxygen, if you use an oxygen supply). I have never seen pure O3-gas and I think that making this is very difficult.

maximizing distillation yields from a retort

golfpro - 26-9-2013 at 16:09

Has anyone found a way to get maximum distillation yields from a retort? I have a 500ml retort and from 200ml sulfuric acid and 160g KNO3, I get 50ml of Nitric Acid. I am looking for a way to get 100ml Nitric acid per 200ml sulfuric acid.

Maybe the neck slightly more angled down? I know that on a cold day I'd get more HNO3, and with less material in the retort, more nitric acid can be attained, but this only means it's more efficient to use less each time.

I was thinking of a way to cool the neck, maybe with a bag of ice?

I figure there are people on here who used a retort and have found little things for more efficient distillation.

PeeWee2000 - 26-9-2013 at 16:18

Ive never used a retort but the best way I can think of to increase your yield without using an actual condenser would be to stick the end as far as possible into another flask submerged in an ice bath so the entire flask acts like a condenser as well as trying to cool the neck as much as possible.

Theres a good visual of what I'm trying to describe but definitely don't use copper and steel for making nitric acid :D.

You might also try cooling the flask with dry ice, that will cause the nitric acid to freeze but it shouldnt crack your glassware as it does not expand like water.

[Edited on 27-9-2013 by PeeWee2000]

MichiganMadScientist - 26-9-2013 at 16:31

Ah the retort. I own and periodically use a retort from time to time. Unfortunately, they are just not that perfect for good distillations...but not entirely without purpose. The idea is to try and keep the heat at just the minimum you need to distill off whatever it is you are trying to isolate. With the retort, you don't have the advantage of a chilled condenser, so try wrapping the retort in a cold wet rag (and replace the rag with fresh cold wet rags as they heat up). Also, make sure your collection flask is sitting in an ice bath.

Ideally, you can eventually invest in a simple distillation setup. A round bottom flask, a distillation head, a liebig condensor, and a take off. You can probably pull this off for just under a hundred dollars on Ebay. You can even use a simple automotive siphon to circulate water through the condenser. And after you obtain this setup, it's fairly simple to upgrade to fractional or vacuum distillation by simply buying a fractionating column or vacuum adaptor. Then you'll be distilling like the big boys!

[Edited on 27-9-2013 by MichiganMadScientist]

Dariusrussell - 26-9-2013 at 16:33

Another thing I think of (I haven't used retort either) would be to wrap a towel soaked in freezing water (Maybe with some dry ice wrapped inside) and wrap that around the retorts condensing end.
Depending on how long the distillation takes you may have to have a couple of towels ready.
Viel Glück!

OHp, michiganmadscientist beat me to it!

[Edited on 27-9-2013 by Dariusrussell]

Bot0nist - 26-9-2013 at 17:36

Sell it to some sucker whos into "alchemy", and use the $ to buy a proper, ground glass, distillation apperatus...

NO2 removal from anhydrous nitric acid

golfpro - 29-9-2013 at 13:13

I know it's been talked about and I've searched but this thread can just be deleted in 2 days to save space.

If I have Pure Nitric Acid aside from NO2 contamination, how can I remove this without losing the concentration? Some places I see pasing CO2 gasses through drives the NO2 out, sometimes I read just regular air... I've heard of adding small amounts of Urea...

I sat for a few minutes with a pipette making bubbles and saw no color change, is it a much longer process than that? How would urea react w/ the nitric acid to drive out NO2 while keeping it very pure? Or is CO2 needed?

AndersHoveland - 29-9-2013 at 19:03

NO2 is extremely soluble in anhydrous concentrated sulfuric acid, it is taken up and reacts. The reaction can be described by the equilibrium:

2 NO2 + 3 H+ <==> NO+ + NO2+ + H3O+

The nitrosyl and nitronium ions actually exist in the form of nitrosylsulfuric acid and nitronium hydrogen sulfate. Nitrosylsulfuric acid is surprisingly stable, it can even precipitate out as a solid in only moderately concentrated solutions of sulfuric acid (with plenty of water present), though excess water will lead to hydrolysis.

For lower concentrations - say only 90% - the solubility of NO2 drops suddenly because the species nitronium hydrogen sulfate can no longer exist in the presence of water. (However, mixtures of nitric oxide and nitrogen dioxide are easily taken up by more moderately concentrated solutions of sulfuric acid, because then just nitrosylsulfuric acid can form).

In anhydrous nitric acid, however, this uptake equilibrium is not so favorable because of all the nitrate ions present, but I would imagine it still plays a significant role in the solubility.

NO+ + NO3- --> 2 NO2

If you want to rid anhydrous nitric acid of a discoloring nitrogen dioxide impurity, the best route may be to pass a flow of dried ozone in, to oxidize the NO2. This should only be used to remove the last remnants of NO2 impurity that cannot be removed by other methods first used.

[Edited on 30-9-2013 by AndersHoveland]

Bot0nist - 29-9-2013 at 19:28

I have had success by passing dry air from a fish tank bubbler through a drying tube into a graduated cylinder of nitric acid. In the morning, the 100ml of acid was very clear...

AndersHoveland - 29-9-2013 at 19:35

One thing to consider is that anhydrous nitric acid is very deliquescent, it will pull out traces of moisture from any gas being passed through it. If a large volume of gas is being passed in over an extended period of time, it may be important to ensure that the gas is free from moisture. This can be achieved by passing the gas through a column of finely pulverized baked calcium chloride.

CO2 seems like a good gas to use to help pass out and displace most of the NO2, if there is a lot of NO2 in there. Another possibility may be reduced pressure, though one suspects the acid fumes would probably be very corrosive on your vacuum pump.

[Edited on 30-9-2013 by AndersHoveland]

chornedsnorkack - 30-9-2013 at 04:28

How efficient is crystallization for HNO3 purification? The melting point of nitric acid is -42. Is slightly impure HNO3 (traces of water, NO2 et cetera) in the -40-s a viscous substance that is poorly crystalizable, or is it easily frozen leaving excess water and NO2 in the liquid?

golfpro - 30-9-2013 at 10:21

Ok, if I bubbled CO2 gas continuously for 10 minutes through would this do it? I know there are many variables, but I'd like to know if that would be a 10 hourish process or 10 minutes.

68% concentration of a solution, by weight or volume?

golfpro - 15-10-2013 at 18:55

If we have 1L of 68% Nitric acid, is there 680ml of pure HNO3 and the other 320ml is water? Or is 68% of the Liter By MASS composed of pure HNO3 with the rest being water?

[Edited on 16-10-2013 by golfpro]

gsd - 15-10-2013 at 19:03

My understanding is when nothing else is specified, the concentration is in "weight by weight" (w/w) basis. So when you have 1 lit of 68 % Nitric acid you actually have 1 * (density of 68% HNO3) * 0.68 kg of 100% HNO3 dissolved in 1 * (density of 68 % HNO3) * 0.32 kg of water.


by weight

quantumchromodynamics - 15-10-2013 at 22:32

68% nitric acid means 68% of the weight is HNO3 and 32% of the weight is H2O. The density of HNO3 is going to be different (thicker) than the density of H2O, so the volume of HNO3 is going to be less than 680ml per liter of acid. You need the density of nitric acid to compute relative volumes.

*FWOOSH* - 15-10-2013 at 23:26

I'll back up the previous answers. A solution expressed in % is always a proportion of solute mass to total solution mass. 68% HNO3 means 0.68g HNO3 per 1.00g acid solution. The other 0.32g should be water in this case, but this won't be the case with every other solution out there (stabilizers, buffers, etc). I generally always convert % to M as a matter of personal preference, mass ratios can be misleading.
For example:
-Large molecules (especially if you get into organics) can have very high mass % concentrations and still be quite low in molar concentration.
-1L of solution is NOT equal to 1000g of solution. This is a characteristic of water at room temperature.
-You really shouldn't measure out a mass% solution by volume unless you've done the proper calculations (densities, Molarity, etc).

My two cents:P, sorry if I ranted, this insistence on % strength ratings has always been a pet peeve.

NaNO3 instead of KNO3 for nitric acid distillation

golfpro - 23-10-2013 at 17:47


I have lost my source of KNO3 which I distilled from H2SO4 to produce HNO3, I may no longer be able to produce 99% Nitric acid unless I find something to replace the KNO3, so would NaNO3 work as a substitute here?

there is more Nitrate concentration w/ sodium nitrate than potassium nitrate..

Kind of weird, Lowes, Home depot, and Walmart all pulled stump remover off of their shelves seemingly in the same day.

[Edited on 24-10-2013 by golfpro]

elementcollector1 - 23-10-2013 at 18:09

NaNO3 will work just fine. Make sure to readjust the stoichiometry as needed. Ammonium nitrate from cold packs works as well.
(I wouldn't give up so quickly - even if all your OTC sources disappear, there are always online sources...)

golfpro - 23-10-2013 at 18:14

I hate ordering chemicals online but I might have to. I read about using ammonium nitrate for this and it won't work as well because of side reactions as well as safety issues.

Moderator Warning

bfesser - 23-10-2013 at 18:46

golfpro, stop opening new topics to ask short questions. Use a search engine.

I've merged <em>nine separate topics</em> on HNO<sub>3</sub> from you! No more warnings; from now on, I will delete any new topics you open.

cal - 24-10-2013 at 01:58

Quote: Originally posted by golfpro  
I hate ordering chemicals online but I might have to. I read about using ammonium nitrate for this and it won't work as well because of side reactions as well as safety issues.

I made it frron sodiium nitrate and sulfuric acid in about 3 hours and distilled it with out any problems.

Zyklon-A - 22-3-2014 at 11:16

Quote: Originally posted by Pulverulescent  
How is 100% Nitric acid attained?

N2O5 is dissolved in azeotropic HNO3 to bring concentration up to 100%!

I know this is an old post, but do you, or anyone have a reference for this?

hissingnoise - 22-3-2014 at 12:44

I don't have one to hand but it is hardly needed as the method is easily understood ─ however difficult to practice?
Also, NO2/O2 fed to the azeotrope under pressure can attain up to ~98% HNO3!

Think I'll stick with the ~96% HNO3 I get from ordinary distillation!

Zyklon-A - 22-3-2014 at 14:05

So would the equation be:
N2O5 + 2H2O → 2HNO3?

hissingnoise - 23-3-2014 at 04:21

Yep! All that's required now is a N2O5 generator and some water . . . ?

Zyklon-A - 23-3-2014 at 13:34

Well never mind, looks like dinitrogen pentoxide is too expensive to be useful as a precursor to nitric acid.

otonel - 11-2-2015 at 14:29

I read in an old book about distilling nitric acid using steel retort, and right now I want to build or improvised one because i want to make some lead nitrate and I need diluted nitric acid.
What do you thing about this improvised distillery can work ?
I read on a forum about a "recipe" to make nitric acid without distillation but how pure can be the final product because i don`t want sulfates in my nitrate.


Nitric acid Reaction:
-Bring 100 mL of Distilled Water in a 500 mL pyrex beaker to 212F (100 C)
-Add the Nitre of your choice (202 gm K / 170 gm Na) -Stir until Nitre is completely dissolved, let cool below boiling
-SLOWLY add 56 mL concentrated (96%+) Sulfuric Acid to Hot Nitre solution while stirring. DON'T allow the solution to boil! -Allow solution to cool to room temp (DO NOT SKIP - VESSEL WILL SHATTER IF PUT ON ICE WHILE HOT!!!)
-When vessel reaches room temp 77F (25 °C). Put the vessel in the freezer or on a salt water ice bath -Let stand until temperature of mixture reaches -41F (-5 °C)
-Let stand at -41F (-5 °) until all precipitate settles
-Pour the COLD solution off into glass container with tightly sealed lid DO NOT POUR OFF ANY OF THE SALT IN THE BOTTOM!!! Makes ~160 mL ~ 50% HNO3

inst.jpg - 748kB distil.png - 102kB

Molecular Manipulations - 11-2-2015 at 15:17

The process described is indeed distillation, it's just a simpler setup.
If done perfectly there should be very, very little sulfate in the distillate. If you use an excess of nitrate there should be even less.
But perfection isn't possible, and while very little sulfuric acid will volatilize, aerosols may be a major cause of contamination of not just sulfuric acid, but also Na/KHSO4. Using boiling chips will alleviate the problem, but I can't think of a way to completely prevent contamination.
BTW, your "beaker" doesn't look like it could handle the heat. Also if that's a plastic coke top, it will catch on fire, but that shouldn't be a big problem right?
Actually I can see that it's glass, nice job cutting that, diamond blade?

[Edited on 11-2-2015 by Molecular Manipulations]

Bert - 11-2-2015 at 15:17

About your quoted procedure- Just for a start: -41 F is approximately -41.5 C, NOT -5.1 C!

Your drawing may be workable- Particularly f you can can cool the small jar receiving the condensed nitric acid. Some have done what you diagram, but added a ceramic or glass "stool" of some sort to keep the receiver above the hot nitrate/Sulfuric acid in the bottom of reaction vessel.

The second procedure in the below linked video starting @ 2:10, reacting a nitrate, Copper metal and hydrochloric acid while piping the nitrogen dioxide into a hydrogen peroxide solution will give you useable nitric acid without sulfate contamination-

cyanureeves - 11-2-2015 at 18:53

yes its been done BUT if the "big glass jar" is not heat resistant you may have a serious and i mean dangerously serious situation.surely you werent gonna use that pickle jar looking thing?

Marvin - 12-2-2015 at 17:20

Everyone can see that the text and the pictures otonel posted are two completely different processes right?

Both methods are dumb for different reasons, the one in the pictures is very dumb.

It might be preferable to make dilute nitric and distil than to make concentrated acid and dilute. If nothing else less toxic gasses should be produced. Lead nitrate is a persistent poison. This sounds like a very green student wanting to do something stupid so he can do something much more stupid.

Bert - 12-2-2015 at 22:54

Indeed, I missed the drawing not having a "bath", putting a non Pyrex container full of acid on a hot plate is asking for a disaster.

otonel - 13-2-2015 at 04:20

I understand how dangerous is lead nitrate and working with acids especially nitric acid, You have right about glass jar if it is not heat resistant can make a disaster, that picture with the jar is not my "opera" and my mother when make pickle put the glass jar in a pot and warm the water for better preservation, and the jar don`t have fissures after that.
In this weekend I want to try this distillation and I will tell about the result.

[Edited on 13-2-2015 by otonel]

Bert - 13-2-2015 at 08:52


Read up on heating "baths"-

Water, brine, oil, sand, even metal shot.

If you still plan to put a glass jar directly on a hot plate, PLEASE try it once with nothing but water inside.

otonel - 13-2-2015 at 13:37

Sorry for the misunderstanding, I will use pyrex container placed on a water bath sealed (not perfectly) with glass and heat resistant silicone .I do not want a perfect seal because the heating increases the volume and a perfect seal can cause problems
I want to say a normal jar can be use if it is placed in a pot with water and this is slowly heated from a hot plate

macckone - 13-2-2015 at 19:43

Canning jars are fairly resistant to thermal shock.
You really need an oil bath but I use them for various reactions
And haven't had one break. I wouldn't use direct heat on one though.
Safety first.

cyanureeves - 13-2-2015 at 20:43

negative gentlemen, stop this crazy idea about using this kind of glass.there are many shaped glass coffee vessels that can stand heat better than soda lime glass.some coffee glass pots are even shaped as erlenmeyers and beakers and can withstand a lot more heat than ordinary glass.i have used glass coffee pots on live fire and even propane flames,some have shattered upon cooling also.cease and desist now and be safe.

otonel - 14-2-2015 at 06:57

Improvised distiller at work in pics, it worked well with the condition to change top water at 5 minutes using a syringe.
Nitric acid obtained is concentrated and emits red smoke.
I am glad for successful experiment and it can be improved , especially the heat exchanger

Fotografie0304.jpg - 290kB Fotografie0305.jpg - 213kB Fotografie0308.jpg - 231kB

cyanureeves - 14-2-2015 at 07:01

very good otonel.

Molecular Manipulations - 17-2-2015 at 06:36

What concentration did you get?

otonel - 17-2-2015 at 12:14

I don`t determined the concentration because I diluted it anyway for use in what I need and do not emit toxic fumes.
After aspect I think is somewhere in the 70 % concentration