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Author: Subject: Nitric acid
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thumbup.gif posted on 26-6-2003 at 07:08


Liquefying NO2 isn't hard, it's boiling point is 21.1C (this has been taken from a Material Safety Data Sheet for N2O4 - liquefied NO2).
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[*] posted on 16-7-2003 at 05:33


If I were to use the conc. H2SO4/KNO3 method with an oil bath and a pyrex distillation setup (a condenser), then distilled at about 65C so no H2O would evaporate (I think 65 is the evap point of HNO3), would I have 100% HNO3 (or close to 100%)? Would the final product be sufficient for RDX manufacture?
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[*] posted on 16-7-2003 at 10:15


You should use a bit of excess H2SO4 since it has high hydroscopicity and will hold any water from going through the condensor but really you should be just using 98% H2SO4 from the start so there is barely any water anyway. Keeping the temp at 65C is good to do because it will help prevent the HNO3 from decomposing although I think you could take the oil bath to 70C. If you have to ask these questions about HNO3 distillation then you're not ready to make RDX.
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[*] posted on 16-7-2003 at 10:25


Oh, I am ready to make RDX, I have been doing this stuff for many years, it is just that I was reading up and some people are saying that a simple distillation won't yield anywhere near 100%. Since >95% is necessary for RDX, I dont want to waste my time and money on the glassware if it will be <95%, as nothing else I am planning to do will require >70% (which I can just buy)...
Do you think I should spring for the glassware (condenser, teflon stoppers, ect.) or not bother? RDX is my main goal with this and if its no dice on >95% HNO3 then I won't bother spending the money.
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[*] posted on 16-7-2003 at 12:39


I think what they meant is that normal distillation of HNO3 can't yield a concentration higher than about 70% because it forms an azeotrope with water at 68% HNO3 so that you can't get higher than that unless H2SO4 is used to keep the water from evaporating with the HNO3. A proper condensor and teflon stopper isn't necessarily needed. I've recently had success making nitric acid of concentrations of around 95% with a very improvised still. It's a large glass jar/beaker with H2SO4/NH4NO3 mix in it, in the center of that is a glass or other acid resistant stand(I used a small glass jar), on the stand is a small beaker/glass jar. The opening of the large jar is covered with a HDPE sheet sealed on with a rubberband. Ice is placed on the sheet with it loose enough to dip down in a bowl shape. For mine I actually use part of a light fixture that is like a glass bowl with a conical bottom. Anyway, this is put in a hot water/oil bath kept at 60-70C. I've used my set up three times giving me like 95% HNO3 each time and about 7.5-10g per 2 hours. Look on brain fever's site for some pictures of a still like this. Also you could get some teflon tubing on ebay to make a condensor, I just recently bought 250ft of 1/8" inside diameter to make a still with.
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[*] posted on 17-7-2003 at 05:09


Thanks, I may have to try that... or just buy the apparatus off of ebay....
Have you had success using your HNO3 to make RDX?

[Edited on 17-7-2003 by VoD]
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[*] posted on 17-7-2003 at 12:59


Haven't tried RDX yet. Actually I'm just planning to do my first nitroaromatic in the next few days. So long as you use 98% sulfuric acid with the KNO3 to distill the nitric from it should be 95%+ nitric and pure enough for RDX.
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[*] posted on 17-7-2003 at 14:57


I have 98% H2SO4, however it is drain cleaner so it is dyed.... that shouldn't matter though I suppose. I plan on using KNO3 instead of AN, so I guess I will do the calculations and give 'er. I don't like how ghetto brainfever's setup is though, so I may try something a little different though...
How do you plan on using the teflon tubing for a still?
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[*] posted on 17-7-2003 at 17:10


I intend to take a flask and stopper it with a teflon stopper(my uncle bought a lot of plastic including a bunch of teflon from a distributer that was going out of business, he also has the tools to machine the stopper). Then I'll have one hole in the stopper with the tube sticking directly in it, from there I will wrap the teflon tube in a single layer several times around an ice-filled bottle, after that the tube will just drip into another flask. Considering that the tube is only 1/8" internal diameter I might have like 5 holes in the stopper for five tubes and just have them wrapped side by side around the same bottle of ice so I can condense more at a time. Heat will still be with hot water or oil kept at around 70C. I made a quick illustration of it here:

http://www.geocities.com/nitric63/teftube.gif
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[*] posted on 18-7-2003 at 18:17


Calcium oxalate is insoluble as all hell, maybe Ca(NO3)2 + H2C2O4 ---> 2HNO3 + Ca2C2O4 but I dont know how the oxalate would fair in such an increasingly acidic enviorment. Another worry would be Oxalic acid being precipiated out before the reaction is anywhere near complete due to it being a weak acid and the equilibrium being shifted due to increasing pH of the solution, anyways, it's just a thought, maybe more manageable then the CaSO4 precipiate, maybe a constat system at high temperature could be done with slow addition of the nitrate to a oxalate solution with effient boiling off of the nitric acid as it is formed keeping equilibrium favored.
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[*] posted on 18-7-2003 at 22:53


This is just a thought I've been having. Whenever people do the precipitation method they add all the Calcium nitrate at once and can get none or little Nitric acid. What if you added it in portions. Add an amount, then filter. Add another amount and filter again. This would increase the amount of nitric acid everytime. I'd imagine that a smaller amount of precipitate could be pressed harder to remove the remaining acid as well.

This has been running through my mind for a couple days. I've been trying to figure out what wouldn't work. I can't find a reason for it not to. I know its far from perfect, but it may be a way to get a signifigantly larger amount of very high purity Nitric acid in a relitively small amount of time.
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thumbup.gif posted on 23-7-2003 at 07:58


How about this:
1) 2NH4NO3+Ca(OH)=>2NH3+2H2O+ +Ca(NO3)2
2)2Ca(NO3)2(heat)=>2CaO+4NO2+O2
3)4NO2+O2+2H2O=>4HNO3
:):cool::o
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[*] posted on 23-7-2003 at 17:13


I don't know about that decomposition of calcium nitrate, usually nitrates decompose along the lines of

Ca(NO3)2 ----> CaO + O2 + 1/2N2

although I know some nitrates favor decomposition to nitrogen dioxide such as lead nitrate.

Pb(NO3)2 -----> PbO + NO2

This reaction is very reliable and easy with the exception that the lead monoxide attacks glass so take some aluminum foil and use it to line your flask, any oxygen or nitrogen impurities should not bother your dissolution into the water so no worries there, this reaction gives a good yield and is quite controllable. Supposedly it decomposes around 470 C. That actually seems a little high, maybe it was basic lead nitrate... 3PbO*N2O*H2O nahhh, the formula makes it seem like it would let up that water molecule and the molecule of nitrous oxide, regardless, I've got a nice jar of it in my lab from the 1800s that reads [Plumbous Nitrate For Making Nitrogen Tetroxide] goes right along with my jar of iron sulphide, notice the p in sulfide, good ol' vintage chemicals.
:D

Oh yeah, and this:
2NO2 + H2O ---> HNO3 + HNO2
but nitrous acid decomposes easily expecially if you elevate the temperature a bit
3HNO2 ----> HNO3 + 2NO + H2O
from here you could react the nitric oxide that comes off with more oxygen and put it back into the system. One more thing, there is an equilibrium
2NO2 <----> 2NO + O2
as the temperature rises it gets more and more toward the NO side and if oxygen gets out of the system they will not recombine and you'll end up bubbling mostly NO though your water unless you have an efficent condenser. Like I said, the decomposition reaction above seems a little high but if it is running that hot I'm glad I've got my condenser running.

[Edited on 24-7-2003 by BromicAcid]
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[*] posted on 23-7-2003 at 22:06


Quote:

Ca(NO3)2 ----> CaO + O2 + 1/2N2


Small error: ;)
Ca(NO<sub>3</sub>;)<sub>2</sub> <sup><u>&nbsp;<font face="symbol">D</font>&nbsp;</u></sup>> CaO + <sup>5</sup>/<sub>2</sub>O<sub>2</sub> + N<sub>2</sub>

Thanks for the great bit about Pb(NO<sub>3</sub>;)<sub>2</sub> <sup><u>&nbsp;<font face="symbol">D</font>&nbsp;</u></sup>> PbO + 2NO<sub>2</sub> + <sup>1</sup>/<sub>2</sub>O<sub>2</sub> :)
I wanna liquefy N<sub>2</sub>O<sub>4</sub>. :D




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biggrin.gif posted on 23-7-2003 at 23:05


sorry, big error:
where did you get the idea that nitrates decompose into N2?

Almost all metall nitrates decomposes into some nitrogen oxide. The heavier the metall nitrate, the more favour of NO2 :) and generally lower decompostion temperature too (depends of course on the stability of the nitrate ) Lead and copper almost entirely decomposes into NO2 and metall oxide.

Since Cu (NO3)2 formes a hydrate with low melting point , you will actually distill of HNO3,H2O, NO2 from it when heated !
Not nice when you dont know about it ....
cough, coough...

Ca(NO3)2 decomposes into NO2 ,NO, N2 and O2

rougly Ca(NO3)2 => CaO + 2 NO2 + 1/2 O2 starts at around 500 C, melting point for CaNO3 is 560 C, where decompostition is vivid.

But because of the high temperature much of the NO2 decomposes into NO + O2, but later when temperature is reduced , NO2 forms again.

All taken from Gmelin and Ullmann. I havent tried in real life, but when Ca(NO3)2 is heated strongly there is a faint brown gas emitted, sofar I have come. It is time to build a retort

[Edited on 24-7-2003 by rikkitikkitavi]:D:D

[Edited on 24-7-2003 by rikkitikkitavi]
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smile.gif posted on 24-7-2003 at 09:46


So it WOULD work after all...:cool:
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[*] posted on 24-7-2003 at 18:37


Sorry about that, never decomposed calcium nitrate by it's lonesome, I'm used to working with nitrates in pyro and therefore with a good fuel you get pretty much all oxygen probably because any NO2 formed is going to be an active oxidizing agent. I was sure about the lead nitrate though. Anyways, in the future decomposition of nitrates will be duely noted as being not as straight foreward as I would like to believe.
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[*] posted on 25-7-2003 at 00:17


according to litterature it will work, but wether it is possible IRL we have to do experiments. Perhaps yield isnt so good.

/rickard
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sad.gif posted on 31-7-2003 at 08:35


OOPS... the problem is where we least expect it (more so if you need anhydrous HNO3).
4NO2+2H2O+O2=>4HNO3, eh...
Well if it's 70C, 50atm and 4 hours (for anhydrous HNO3)!
Sorry...:o:mad::(
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[*] posted on 3-11-2003 at 07:42
HNO3 Percentage vs Density


Has anyone got a detailed chart for the percentage of HNO3 vs it's density? Often they quote densities but not the percentage... any sources anyone?
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[*] posted on 3-11-2003 at 10:37
% in what? H2O?


What are you looking for? The density of x solution of HNO3 in water? For water it's easy. Calculate it. You know the ratios of the components of the solution,the weights, volumes, and densities,of both.

Calculation time. :)




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[*] posted on 3-11-2003 at 12:22
well well... might not be that easy!


well, of course it's H2O. If it was another solvent (like what exactly? D2O , DCM, H2SO4?) I would have mentioned it.

I thought that one might calculate it, however, it might be possible (though I dont know) that the density of a mixture of solvents increases/decreases non-linearly with increasing one over the other.
What I mean by this is that two different solvents of different densities don't necessarily behave according to

density_final =
(density1 x volume_solvent1/volume_total) + (density2 x volume_solvent2/volume_total))

when mixed.

For instance, the density of solvent1 is 0.5, and that of solvent2 is 1.5. I take 50 units (teaspoons , gallons, ml ;) ) of each. Thus you would immediately guess the final density is 1. Using that equation works of course. I.e. density_final = (0.5x50/100)+(1.5x50/100) = 1.

However, I am sure there are cases where the solvent spaces (i.e. spaces between the two types of molecules) enable the final density of the two solvents to go up (or down?), that is the final volume decreases (I guess this depends on molecular size, shape, van der Waals & electrostatic forces, and even chemical reactions such as H2SO4+H2O --> [H3O+] + [HSO4-]) so it would be a solvent-specific system, hence not predictable) ! In the above case, 50 ml of solvent 1 plus 50 ml of solvent 2 would be LESS than 100 ml when mixed.

So, how do you know this is not the case, primopyro? See, that's the reason I was asking :)

So again, anyone got a % vs density chart of HNO3 in H2O? :P

Edit: In fact I just remembered that I did this calculation once with HNO3 and a few known densities/%'s. Surprise surprise, the theoretical value was DIFFERENT from the real one, kind of making a chart necessary!

PS Primo I am waiting for an answer! ;)


[Edited on 2-12-2003 by chemoleo]
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[*] posted on 2-12-2003 at 01:34


A good example is water + ethanol;
mix 50ml of water and 50ml of ethanol and you end up with 96ml of mixture.




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[*] posted on 5-12-2003 at 16:35
Density Chart of HNO3


Finally found it, in the roguesci archives. For anyone curious, yes, it is HNO3 in WATER, not D2O etc :D :D

w[%] d[g/ml]
0 1.0000
1 1.0036
2 1.0091
4 1.0201
6 1.0312
8 1.0427
10 1.0543
12 1.0661
14 1.0781
16 1.0903
18 1.1026
20 1.1150
22 1.1276
24 1.1404
26 1.1534
28 1.1666
30 1.1800
32 1.1934
34 1.2071
36 1.2205
38 1.2335
40 1.2463
42 1.2591
44 1.2719
46 1.2847
48 1.2975
50 1.3100
52 1.3219
54 1.3336
56 1.3449
58 1.3560
60 1.3667
62 1.3769
64 1.3866
66 1.3959
68 1.4048
70 1.4134
72 1.4218
74 1.4298
76 1.4375
78 1.4450
80 1.4521
82 1.4589
84 1.4655
85 1.4689
86 1.4716
87 1.4745
88 1.4773
89 1.4796
90 1.4826
91 1.4842
92 1.4873
93 1.4886
94 1.4912
95 1.4932
96 1.4952
96.5 1.4972
97 1.4988
97.5 1.5005
98 1.5008
98.5 1.5044
99 1.5066
99.5 1.5091
100 1.5129

See also the Calculation Concentration thread for more ....

[Edited on 6-12-2003 by chemoleo]




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[*] posted on 21-12-2003 at 19:41
There is a better way!


If you could get methylene chloride lucky you! cos you could make >98% nitric acid easily.

make a solution of 45mL 98%sulphuric acid and 55mL 70% nitric acid, let cool to room temperature and add 100mL methylene chloride. Stir for 2minutes, let the liquid settle and extract the methylene layer into a sealed container. Pour into the acid another 100mL of methylene chloride and repeat for up to 8 times. The nitric acid will form a complex with methylene chloride but water and sulphuric acid will not dissolve at all.

when all 8 extractions are complete, distill the methylene chloride solution to yield methylene chloride at the condenser and pure HNO3 is left behind. this is easy since methylene chloride boils at 41degrees Celcius. yield is about 80% of the nitric acid (not taking into acount the water) began with.

the sulphuric acid can be recycled if wanted by heat-concentrating. the methylene chloride is used for another batch.

Where i live (australia) i could find a solution of 87% methylene chloride in methanol, used as a remover for dry paint, and i believe you could extract pure methylene chloride by adding equal amount of water to the methylene/methanol solution, and extracting the insoluble methylene chloride.
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