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Author: Subject: Our Beloved Nitric Acid
DetaDude
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[*] posted on 5-10-2009 at 17:06
Our Beloved Nitric Acid


Since alot of what we do involves the use of this valuable commodity (especially the energetic materials crowd) I thought that a new post on this topic might be in order. I know this topic has been talked to death in other posts & threads, however I would like to hear from some our more advanced and experienced citizen chemists (no I'm not one of them).

The idea behind this post/thread is to amass some plain vanilla type info for our more basic and novice people.

I am 68 yrs old and have been at pyro/chemistry/explosives since age 11. That said I would like to generate on this post a wealth of knowledge on the topic of just nitric acid.

What works and what does not, what is better vacuum or non vacuum distillation, column or no column, ratio of H2SO4 to HNO3 when distilling if it is even used, alternative methods to concentrating/purifying etc., etc., etc.

When I need a high concentration of HNO3 I use 70% HNO3 and 96% H2SO4 under 29,5 in. Hg with a column and get excellent results, to wit 98% HNO3. But this is just my method how many other ways are there to boost the percentage of HNO3, and are there any heavy expenses involved?

Please try to keep it plain vanilla, at least freshman high school chemistry, remember I would like this to be for the lay person.

Thanks ahead of time to all those that respond




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Rich_Insane
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[*] posted on 6-10-2009 at 18:49


:o You and I live in the same area.

I am having trouble just making 70% HNO3. Mostly because H2SO4 is in Ace hardware and I can't drive, and I don't have a legitimate distillation system.

I must say, there is already a stickied thread about HNO3 production.
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ammonium isocyanate
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[*] posted on 6-10-2009 at 19:09


Depending on quantity, you don't really need any fancy equipment to make nitric acid.

I made about 20mL fuming nitric acid using the following apparatus:

A 50mL beaker was placed inside a 250mL beaker, and the to the outside edge the 250mL beaker was added sodium nitrate (anhydrous) and 98% sulfuric acid (1 to 1 molar ratio). A funnel with the stem broken off (the stem was already broken-- I didn't break it off just for this) was placed over the 250mL beaker (which it just covered, leaving a small opening where the spout was) such that the funnel was centered over the 50mL beaker. Several small strips of Teflon tape were balled up and used to plug the funnel so that it would hold water (which worked suprisingly well- no water ever came through it). The funnel was then filled with crushed ice. The apparatus was then placed on wire gauze and heated over a burner until distillation ceased.

I didn't do quantitative analysis of the nitric acid, but it was light yellow, presumably due to dissolved NO2. The nitric acid reacted vigorously with silver to produce AgNO3 and brown fumes of NOx.




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Rich_Insane
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[*] posted on 6-10-2009 at 19:23


I see how that'd work. Now I have to get some 50 ml beakers....

Well, I was thinking of producing 100 ml of HNO3 at a time, as opposed to buying 2.5 L of HNO3 at ridiculous prices. I only really need it for nitrations ATM.
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halogenstruck
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[*] posted on 10-10-2009 at 11:54


it is not concentrated,i suppose.
con. HNO3 does not react vigorously with Ag as silver nitrate is sparingly soluble in concentrated aid and makes a protective layer which protect it against furthur reaction.
i know it for 60%-50%
but maybe it`s not correct for over 80% as i did not used it over Ag before.
30% and lower corrode silver good
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blogfast25
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[*] posted on 10-10-2009 at 12:26


Quote: Originally posted by halogenstruck  
it is not concentrated,i suppose.
con. HNO3 does not react vigorously with Ag as silver nitrate is sparingly soluble in concentrated aid and makes a protective layer which protect it against furthur reaction.
i know it for 60%-50%
but maybe it`s not correct for over 80% as i did not used it over Ag before.
30% and lower corrode silver good


It would help if ammonium isocyanate could quantify a bit by weighing the nitrate, sulfuric acid and the obtained nitric acid using his distillation method. This could give rough idea of yields and concentration of the nitric. Otherwise, titrate with NaOH...
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halogenstruck
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[*] posted on 11-10-2009 at 12:50


yes u r right,method is genius and adding some details about the yield could be a good idea.
also i would add up to my last post here,i think if Ag is not completely pure like containing 10% Cu which is normal,it may dissolve much vigorously.
i had 99%HNO3 and it was yellow too.it is possibly because of dissolved NO2/NO gases.
although i think concentrated solutions of NO2/HNO3 tends to be green.when exposed to air,turns to colorless due to NO2 loss
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hissingnoise
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[*] posted on 12-10-2009 at 04:58


N2O3, dissolved in HNO3 colours the solution green. . .
NO2 is always amber in colour.
The dimer N2O4 is colourless!
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[*] posted on 12-10-2009 at 17:54


I no longer have the old sample of nitric acid which I obtained using the method I described, so I rebuilt my apparatus today and ran a small scale test. If absolutely necessary, I will perform a titration on the sample I produced to verify concentration.

Apparatus:
-Outer beaker was 150mL
-Inner beaker was 50mL
-Funnel, 75mm, with a broken stem, was plugged using wads of teflon tape and placed resting on the lip of the outer beaker with the remainder of the stem located directly above the inner beaker.
-Reactants were poured into the gap between the inner and outer beakers.
-Funnel was filled with ice water.

Procedure:
4.84g of anhydrous sodium nitrate was added to the outer beaker, followed by 6.22g of sulfuric acid (an 11% molar excess assuming end product is NaHSO4). The plugged funnel was filled near the brim with ice water, and the whole apparatus was heated over a burner on low heat until distillation from outer beaker slowed significantly and the beaker became red-brown from nitrogen dioxide. The apparatus was set aside to cool, and the funnel was removed. 2.0mL of distillate was isolated, density 1.48g/mL (theory, 100% nitric acid, 4.52g/mL, 70% nitric acid, 4.42g/mL), which in contact with air fumed to produce a white, highly irritating, generally nasty mist.

Conclusion:
This method requires very little in the way of glassware, and appears to produce fuming nitric acid (based on density and qualitative observations). It could also likely be scaled up with ease to several times the scale used in this experiment. Furthermore, it is likely that one could use less sulfuric acid, substituting greater heat in order to drive the reaction to Na2SO4. However, even with these modifications, it is unlikely that a large amount of nitric acid could be produced by this method.

Apparatus:

Nitric acid distillation.jpg - 232kB




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halogenstruck
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[*] posted on 12-10-2009 at 18:35


it fumes because it vaporizes to air but with the steam in air makes its azeotrope with water with higher boiling point and lower volatility.as a result it condenses again as small droplets and makes white fume.it fumes only in humid air.sometimes it makes fume because of NH3 in atmosphere
good job,u made a concentrated HNO3 with a simple apparatus
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[*] posted on 12-10-2009 at 18:39


Yes I figured the fuming was as such. The air where I live is almost always humid, so as such I always deal with such things. The fuming really was impressive though, much more than 37% hydrochloric acid.



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[*] posted on 19-10-2009 at 17:27


Acid produced by conc. H2SO4 / NaNO3 reaction is not anhydrous it's just about 95-97% in general and contains some nitrogen oxides witch are unacceptable in some nitrations since NOx promote oxidative action of acid. To make pure colorless HNO3 from acid mentioned above, one must measure it's density and dehydrate it using calculated ammount of P2O5, remove NOx by passing stream of dry air or CO2 and finaly distill it in vacuum.

[Edited on 20-10-2009 by Engager]




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[*] posted on 20-10-2009 at 08:56


a drop of H2O2 maybe makes completely white although a little bit diluted
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[*] posted on 20-10-2009 at 10:30


My 5 cents on concentrating HNO3: instead of using the expensive and hard to find DCM (dichloromethane) for extraction, just use plain old magnesium nitrate anhydrous. It'll dty the nitric acid very well, leaving it white pure.

No farting around with distillation setups and such.
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[*] posted on 20-10-2009 at 11:52


AFAIK, Mg(NO3)2 is usually supplied as a hydrate and trying to dehydrate it by heating is fruitless as this salt is decomposed by heat.
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[*] posted on 20-10-2009 at 16:05


Well, the simplest method (and the one I happen to use) simply involves taking almost any nitrate salt (potassium, sodium, etc.) and placing it within an erlenmeyer flask. You then add some 33% hydrochloric acid to the mix, stirring so that all of your nitrate salt dissolves in the acid- water mixture. You should then prepare the apparatus; a second erlenmeyer flask, containing water. As well, ready a holed stoppers (coated in teflon or something of the sort, as nitric acid can eat through certain types of rubber) as well as some tubing (check if the material is resistant to nitric acid), which will vent the fumes produced in your first erlenmeyer flask, to the second. Once your apparatus is set up, add copper metal to the HCl/NO3, and seal it off with the holed stopper, with the connected tubing/ piping. The vessel will quickly begin to produce NO2 gas, which gives HNO3 when bubbled through water. Based on your stoichiometry, you can control the concentration of your final solution. (granted your yield will never be 100%)

And I agree about having some sort of publication on making nitric and hydroiodic acid and so forth, for more inexperienced chemists (I don't deny, in some respects I remain in that category). Hell, if it weren't for piling schoolwork, I might do it!
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[*] posted on 20-10-2009 at 16:06


Damn, that shouldn't have been most efficient; not simplest.
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hissingnoise
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[*] posted on 21-10-2009 at 03:34


Your 'method' is more waste of time and nitrate than method. . .
If you want HNO3 in any quantity or concentration get yourself a proper distillation apparatus and forget that other rubbish!
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[*] posted on 6-12-2009 at 20:32


Has anyone tried concentrating nitric with a reflux set up, if so how about a little feed back on how it was done, and the outcome, equipment used, was vacuum involved, did you also use a column, etc.



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[*] posted on 6-12-2009 at 21:07


Quote: Originally posted by DetaDude  
Has anyone tried concentrating nitric with a reflux set up, if so how about a little feed back on how it was done, and the outcome, equipment used, was vacuum involved, did you also use a column, etc.


Why would you try to concentrate anything with a reflux setup?




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[*] posted on 15-12-2009 at 16:39


I guess I should have made myself clearer. The intention was, has anyone tried using a reflux condenser in the distillation of HNO3, with or without a column or vacuum.



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[*] posted on 15-12-2009 at 18:34


Still not clear.

A reflux condenser is not a particular kind of condenser (Liebig, West, Allihin, Friedrichs) but rather a condenser arranged for reflux, to return condensate to the boiler. Any of those types of condensers can be used for reflux.

No one can understand how you can distill this way, for good reason. Try describing exactly what you have in mind if you want a meaningful answer.
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[*] posted on 16-12-2009 at 08:10


If you mean fractional distillation it won't work because there's no way round the azeotrope. . .
Its boiling temperature is always 120*C at normal pressure!

[Edited on 16-12-2009 by hissingnoise]
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[*] posted on 17-12-2009 at 22:08


entropy51:

Sorry but you are amiss with your statement about a reflux condenser. There is a condenser that is made just for reflux operations and it is very similar to a Graham type condenser except the cooling fluid flows through the coil instead of the jacket. This is the item that I had reference to in my earlier post.

I use this item atop a column when distilling certain liquids to increase condensate purity, I also use a vacuum (29.0 in Hg).

I was just trying to get input from others that may have had some experience with this type of setup.




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[*] posted on 18-12-2009 at 06:03


Regardless of whether there is such a thing as a 'reflux condenser', entropy's basic point still stands: if you're *refluxing*, then in theory everything is dripping back into the vessel, so no purification or concentration is going to occur. If on the other hand you're assuming that some volatile fraction (water or w/e) is actually escaping, then what you're doing is more like fractional distillation. I can imagine some cases where a sort of hybrid setup would be useful, say if you wanted to reflux ethanol while allowing aldehyde vapors to escape and condense elsewhere, but that's not really what we're dealing with here...
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