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Author: Subject: Nitric Acid Synthesis
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[*] posted on 2-5-2010 at 09:43


... nice (!), only the direct heating by the spiral might be a bit harsh ... :o and your beautiful retort might be history after a while ...

A bath of molten tin might be a good heat-transfer-medium for such a purpose: Tin is known to have quite a low vapor-pressure, and is therefore used in industrial manufacture of float-glass, where liquid glass rests on a hot tin-bath ...
==> Only the tin should be clean, no lead or arsenic or antimony in it ... !
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[*] posted on 2-5-2010 at 09:51


Quote: Originally posted by Mildronate  
Here you can see my retort, its made from 1liter flash and glass pipe. I use it only for nitric acid.


Here you've poured the powder directly down the snout. Why not get a big funnel, then connect a wide tube to the funnel bottom, then stick that into the snout and slowly pour in the powder? Use a metal rod to swirl around and push the powder down if it gets stuck. That will allow the powder to get down further and not contaminate the nitric acid with potassium. The H2SO4 can be added the same way, even easier. You ought to also have a cooling bath for condensing HNO3.
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[*] posted on 2-5-2010 at 09:53


Its made from pyrex glass soviet analog. I think about 5liter retort. Of course i had cooler too, but retort to my mind is best for nitric acid.
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[*] posted on 2-5-2010 at 09:55


That was first time with my new retort. There was litlle bit of water in it thats way KNO3 is on its neck.
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[*] posted on 2-5-2010 at 09:56


Good idea about funnel thanks
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[*] posted on 2-5-2010 at 11:30


Retorts are very inefficient for HNO3 distillation, but if the receiver is cooled by water from a tap spilling onto it the HNO3 vapours will condense reasonably well.
The standard distillation apparatus is far better suited to HNO3 production.


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[*] posted on 2-5-2010 at 11:36


to my mind retort is better than destilation setup with cooler, i had both.
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[*] posted on 2-5-2010 at 11:50


Whoops! I've just noticed the encrustation of salt in the spout - to my mind it looks a lot like carelessness.

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[*] posted on 2-5-2010 at 11:53


thats true but its because retort was wet from water :(
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[*] posted on 2-5-2010 at 12:09


Does your retort have to be charged through the spout?
If it does, getting reasonably pure HNO3 from it will be very difficult.


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[*] posted on 2-5-2010 at 22:13


of course from spout
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[*] posted on 2-5-2010 at 23:56


Quote:

Heating NH4NO3 has to be done very carefully, as the salt is prone to unstable decomposition, esp. if contaminated; thus synthesis via NH4NO3 is not recommended pathway.


Carefully indeed, but if you meet that requirement it's fine. The temperatures involved here are well below the melting/decomposition temperature of ammonium nitrate (210°C or more) as long as you use a uniform heat source and boiling chips. I did this too and it works very nicely giving near perfect yield. I used fertilizer grade ammonium nitrate and drain cleaner grade sulfuric acid in aqueous solution.

The vapor and reflux inside the column was clear, indicating that no ammonia was being given off from the flask, and the gas scrubber on the vent (which doubled as the condenser cooling water) remained at steady pressure when the distillation had stabilized, indicating that no N2O or other gas was being given off.

Doing an anhydrous distillation under vacuum should be a further improvement.


HPIM1670.JPG - 108kB

[Edited on 3-5-2010 by kilowatt]




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[*] posted on 8-5-2010 at 04:43


A distillation retort should have a separate filling point usually with a ground glass stopper, and also usually at the top when in the distillation position.

The obvious production of brown fumes indicates decomposition on a big scale. Distillation of Nitric Acid requires the use of vacuum to get the boiling temperature below the decomposition temp. Also it is necessary to break the azeotrope to get NA greater than 68%.
At the reduced boiling point under reduced pressure perhaps a hot water heating bath will suffice.

Does anyone have some links or references to reasonable temperatures and distillation vacuums to get white nitric acid. I have ground glass distillation apparatus and and aspirator/filter pump. I can pump iced water through the condenser but do I really need better?
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[*] posted on 8-5-2010 at 11:35


You no need links for vacum temperatures there is universal tables (monograms, i dont know is it correct in english). Nitric acid can easy purifiy from NO2 with air or carbamide. There is no azetrope when you use sulfuric acid + nitrate method.
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[*] posted on 18-5-2010 at 17:56
drying ammonia


Quote: Originally posted by Formatik  
... Drying agent and material. In the bottle above, CaCl2 pellets were used. Other drying agents will work, CaO, Na2SO4, MgSO4, etc. In the industry liquid ammonia is used, so no need for drying.


Note again about these drying agents. I didn't notice it much in my experiment, but CaCl2 (many soluble calcium salts, solubility of ammonia is higher in Ca(NO3)2 than pure water) will fixate ammonia. In fact, ammonia has the greatest tendency to form complexates with dissolved calcium ions than other alkaline earths (see: Dawson, McCrae, J. Chem. Soc. 1901, 79 [II], 1069). From those listed above, CaO is the best choice for drying ammonia. It is less harsh than KOH or NaOH, and won't ruin glass either. According to a chart in Gas Mixtures by Gary O. Nelson, average efficiency of MgO is close to as good as CaO. BaO is the strongest dehydrant suitable. With powders though, there is the extra need to filter for the ammonia so no dust comes over into the catalyst.
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[*] posted on 2-6-2010 at 14:35




So yesterday I made some nitric acid. I used KNO3 and H2SO4 and distilled a clear liquid under aspirator vacuum.
The glass was baked in the oven prior to use, the KNO3 was baked in the oven prior to use, and the H2SO4 drain cleaner was boiled on the BBQ till it was fuming, and it was let to cool off to a use able temperature (unstoppered though).
The density of this nitric acid was 1.497 at standard pressure @ 4 degrees Celsius (did not measure room temperature). I assume this to be around 80-85% HNO3.

It was stored in the fridge overnight (at around 4 degrees c) in a ground glass flask with a ground glass stopper and vacuum grease.

Today I decided to re distill it over sulfuric acid to increase the purity. It came over at about 50c. I mixed equal volumes of my HNO3 and fuming h2so4. This time I left the H2SO4 on the grill while it was fuming, and stoppered it with a ground glass stopper while the flask was still hot (maybe 200c), and let it cool to room temperature prior to adding it to the nitric acid. Again, the glassware was baked in the oven prior to use.

I have measured the density of the nitric acid at about room temperature, and it is only 1.477, meaning the nitric acid is less then 90% after I vacuum distilled it from sulfuric acid. I only distilled half the volume of the nitric acid (started with 100ml hno3 and 100ml h2so4 in the boiling flask, and I stopped distillation at 50ml in the reviving flask.

I was under the impression that this distillation should have left me with like 95%+ HNO3. What the hell is going on?

Someone suggested that water vapor might be getting sucked in through the aspirator, but I find that hard to believe, as other members on this board seem to be getting 95+% hno3 using aspirator vacuum.

The KNO3 I am using is pyro grade.


Am I not heating the H2SO4 enough? I heated it to a point where it was spewing thick, choking, unpleasant fumes.
What is the secret to performing this distillation?
And the scale I am using is a MXX-123, which claims to have a uncertainty of 0.663 milligrams... .
The volume is measured using a 10ml graduated cylinder.
what the fuck this shit??! :mad:

[Edited on 2-6-2010 by Chainhit222]




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[*] posted on 2-6-2010 at 14:40


What is the accuracy of the graduated cylinder? That might be your problem.

Edit: You could perhaps titrate it if you think the cylinder is the source of error?

[Edited on 2-6-2010 by Lambda-Eyde]
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[*] posted on 2-6-2010 at 14:50


How do I find out the accuracy of my graduated cylinder?

edit:
It says it on the cylinder, it is +- 0.1ml

I'm suspecting either my scale or the aspirator leaking water, I might try a drying tube next time, unless someone has better advice. And I do not have the equipment to perform a titration.

[Edited on 2-6-2010 by Chainhit222]

[Edited on 2-6-2010 by Chainhit222]




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[*] posted on 2-6-2010 at 15:01


Quote:
Am I not heating the H2SO4 enough? I heated it to a point where it was spewing thick, choking, unpleasant fumes.

When boiling down dilute H2SO4, a choking steam appears long before the last of the water boils off.
You should continue the boiling until the appearance of the fumes changes from a heavy steam to a much thicker, solid looking white vapour (SO3).
This occurs when the temperature goes over 300*C. . .

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[*] posted on 2-6-2010 at 15:05


Quote: Originally posted by hissingnoise  
Quote:
Am I not heating the H2SO4 enough? I heated it to a point where it was spewing thick, choking, unpleasant fumes.

When boiling down dilute H2SO4, a choking steam appears long before the last of the water boils off.
You should continue the boiling until the appearance of the fumes changes from a heavy steam to a much thicker, solid looking white vapour (SO3).
This occurs when the temperature goes over 300*C. . .


its drain cleaner though, it is like 93% to start with. I boiled it yesterday, and today I just heated it till it was fuming. 200c was an estimate, I have no idea how hot it got. Perhaps this was my problem, I'll try again tommorow.

[Edited on 2-6-2010 by Chainhit222]




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[*] posted on 2-6-2010 at 15:14


H2SO4 holds on to water tenaciously and only when SO3 fumes appear can you say it's ~98%. . .
As it cools it can be expected to absorb some H2O fron the air.
That makes getting the acid to 98% all the more necessary. . .

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[*] posted on 8-6-2010 at 12:41


As hissingnoise said, heat the sulphuric till you choke from the fumes, and your mom is yelling at you that you ruin the whole backyard:)

When it smokes intensely condense some of the fumes to a cold glass plate and touch it with some organic, like tissue paper, if the paper char, continue to contentrate it for further 15 minutes or more.

If I were to make 98% H2SO4 from ~90% drain opener, I would vacuum distill 1/3 of the acid and discard it.

For relatively contentrated nitric ~95% you do not need to use 98% sulphuric, baking flask, drying KNO3 etc, just start to distill over the HNO3 from the reaction mixture and discard the first 1/3 of it. or use it for something else that wont require cc nitric.
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[*] posted on 8-6-2010 at 17:46



Have I been mistaken all this time despite company posts(info elsewhere) who specialize in reconstituting used H2SO4 that 93.3% is the maximum percentage available by heating alone.
Up to 70% little to no H2SO4 is lost, 85% and above is where the majority of H2SO4 vapor is lost to a maximum conncentration of 93.3% Above which simple heating will not increase.So my belief has been 98% by heating alone is a myth.
So if my drain cleaner S.G. indicates over 95% I consider myself lucky and use as is.The only thing I routinely boil is batt electrolyte for nitrations wher purity may be important.HNO3 for drain cleaner is a better use for a sulfuric acid contaminated with god knows though ive had may successful nitrations with drain cleaner.Beings electrolyte is about n the cleanest
H2SO4 I can lay my hands on its probably better used concentrated to 93% w/o impurities and compensating for the slightly lower concentration if needed in nitrations.Saving the possibly contaminated Drain cleaner for HNO3.
Back to the maximum concentration of H2so4 I believe thats dictated by the "azetrope of sulfuric acid/water system of 93.3%
at 338c" (Concentration of sulfuric acid and Its Application;QVF)
I think any chemist is aware of this the net is full of this easily unnderstood, easily available info.Some disagreement here but it is likely the way the ratios measured molar or % and altitude.
The current stuff(drain cleaner) liquid fire appears quite clean(light motor oil) and is 1.835 SP. Gr. 96%-98%? That I dont try to concentrate by any means.Most likely has impurities but none that have interferred as of yet w/mixed acids/nitric distillations.I usually have no use of anything over 68-70%HNO3
which makes dist easy.Even with my archaic retort light yellow HNO3, good enough-Fulminates/ nitrates the like.W/o air aspiration,urea.
[Edited on 9-6-2010 by grndpndr]

[Edited on 9-6-2010 by grndpndr]
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[*] posted on 22-7-2010 at 19:08


I just posted a video to youtube where I made HNO3. watch it if you'd like. :D comments and criticisms welcome....I think I did the math right.

http://www.youtube.com/watch?v=n13n4PoF4L8
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[*] posted on 9-8-2010 at 06:18


Really odd values!

I've just assembled a branded quickfit apparatus to distil 35% nitric to get something closer to 65% at atmospheric pressure. Using a heating mantle the distillation temperature rose from 110 - 120C over a period of an hour and the process was stopped.
On cooling to room temp the SG of the distillate is about 1.10 and the SC of the residue is 1.35. Now considering that the original 35% acid had a SG around 1.23 I've definitely concentrated something but why is the residue the high SG product and the distillate the low SG remainder?

I have limited supplies of any sulphuric so I was hoping to reserve it for the final concentration past the azeotrope point.
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