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stanfield
December 4th, 2002, 04:51 PM
The nitric acid I obtain at the end of my distillation is red. I know there is a way to "remove" the NOx by adding urea, but what I want today is measurement !

How many grams of urea/how much mL of nitric acid.

Furthermore, do I need to heat the acid while adding the urea ?

this "recipe" is very imprecise, inaccurate all over the net...

thanx !

mongo blongo
December 4th, 2002, 05:25 PM
Well the amount of urea used depends on how much decomposition has occurred. I think you also have to bubble a dry stream of oxygen through it. If you can find out how much NOx is in your HNO3 then it would be easy to work out molar quantities.

kingspaz
December 4th, 2002, 06:34 PM
wouldn't it be a fair approximation to place a flask of the acid over a white tile and then slowly stir urea into it until it becomes clear?

stanfield
December 5th, 2002, 12:21 PM
the problem with homemade nitric acid is that it's still yellow-red after purification, there isn't very much differences between the "pure" and the "contaminated" product :)

it's could be possible on white industrial nitric acid.

Otherwise, I never got a problem making PETN but one day, runaway will occur due to this shitty NOx...

mongo blongo
December 5th, 2002, 02:23 PM
If your homemade HNO3 is still red/yellow after purification then it needs more urea. It doesn't matter if it is homemade or not. It is still HNO3 and a red colour indicates that there is still NOx present.
If on the other hand, the HNO3 is still yellow after excess amounts urea have been added, it could be due to sunlight decomposing the HNO3 but this happens quite slowly.

stanfield
December 5th, 2002, 05:20 PM
After "purification", he's yellow (with light red coloration :) ) but during PETN manufacture, red fumes are given off... so this must be NOx ! And I've added many grams of urea ! I don't want to add too much urea because it decreases acid concentration...

see ya !

kingspaz
December 5th, 2002, 05:57 PM
the NOx coming off from the PETN nitration is because its oxidising the PE/PETN. did you get a shitty yield? the oxidation could be a couple of things, too higher temperature or too dilute nitric acid.

mongo blongo
December 6th, 2002, 12:05 AM
Just a thought. If you just added a few drops of water, wouldn't the H20 react with NO2 to form some HNO3? But if that was so then it wouldn't make sense to re-distill the HNO3 with H2SO4 because if there was any water in the HNO3 to begin with it would just react with the NOx to form HNO3 (assuming that there was decomposition in the first distillation).
I think I must have gone wrong somewhere.

stanfield
December 6th, 2002, 05:31 AM
nonono, with PETN, I always got a FUCKING AMAZING yield... I'm just worried about the NOx released.

thanx !

Marvin
December 6th, 2002, 05:17 PM
NO2 forms nitric and nitrous acid when you add water. Adding water wont force the reaction the other way until you only have a very dilute solution. Bubbling oxygen through it does a mixture of oxidising the solution to nitric, and driving off NO2 and NO.

megalomania
December 8th, 2002, 05:08 PM
The bubbeling of air through the nitric acid is quite important. It is meant to be done with the addition of urea, both, together... I forget the exact amount of urea to be added, but I believe it to be quite small per unit volume of acid. I have seen the reference several times, but one would think I would have written it down by now...

I should also add that it is possible to remove the redness by bubbling air into the acid while distilling with sulfuric acid (no urea needed, although it is more effective).

Another note just so nobody gets the wrong idea, while oxygen is the necessary component here to be bubbled in, one does not need pure oxygen, plain old air is sufficient, although in all cases it should be DRY air.

<small>[ December 08, 2002, 04:40 PM: Message edited by: megalomania ]</small>

jarrod
February 3rd, 2003, 05:54 AM
How can normal air be dried before entering a pump (a little fish tank one)
Is it possible to have the air pass through a couple of cigarette filters to adsorb the moisture, or cotton wool?
____________________________
[/////][/////][//////] to pump
"""""""""""""""""""""""""""""""""""""""
inlet hose

air flow---&gt;

I am really not sure so any input would be appreciated, would I decreases acid concentration more than 1% using moist air?

Thanx

<small>[ February 03, 2003, 05:01 AM: Message edited by: jarrod ]</small>

nbk2000
February 3rd, 2003, 07:10 AM
Search the internet with Google using the search term:

"drying air" desiccant

That'll give you a good start. I could tell you how to do it, but that'd be giving you the fish, rather than teaching you how to catch them yourself. <img border="0" title="" alt="[Wink]" src="wink.gif" />

jarrod
February 3rd, 2003, 10:07 AM
Well wise fisherman why we are fishing… <img border="0" title="" alt="[Wink]" src="wink.gif" />

Do you have a method (with some sort of measurements) for adding the urea while the desiccanted (if that’s the word :confused: ) air is being bubbled through the impure acid?
I searched the net and found no actual urea/acid ratios or close to.
I found out from searching the form that it is very little urea to acid. :rolleyes:

I was thinking maybe around 2g to 500ml … for a ball park figure
This is based on my 0 experience and 3.5 hours of searching/reading

So any input is very welcome

Thanx

nbk2000
February 3rd, 2003, 10:52 AM
1 gram urea to 100 grams acid.

jarrod
February 16th, 2003, 07:34 AM
For how long should air be bubbled through the acid?

IPN
February 16th, 2003, 08:38 AM
Why won´t you try it your self.
Test it and then you will know what is the correct time.

Not asking others to do the job for you.

Mic
February 16th, 2003, 11:34 AM
Hey,
Today something that I think was impossible happens ! I found some HNO3 here in Canada !! It's a small hydroponic store that sell some pipe for smoking weed and some drugs that are legal (salvia, legal mushrooms, natural ecstacy, legal peyote, etc...) and they sell stuff for growing weed.. I was there because I wanna buy some salvia and I found HNO3 ! it's a PH-.. Do someone know what is the concentration of this stuff ? They also sell some H3PO4 and some H2O2 35%.
Thank You.
Mic

rikkitikkitavi
February 16th, 2003, 03:23 PM
nitric acid for fertilizer use is usually around 50-53 %, it should be listed on the package according to IATA,ADR,UN e t c transport rules.

/rickard

Dave Angel
September 11th, 2004, 05:41 PM
I think I've finally found a way to get concentrated nitric acid clean of NOx, that I am happy with.

Start with 500mL of 97% technical H2SO4 in a 1L jug, adding as much KNO3 as is feasible before the mixture becomes too pasty to handle, which usually amounts to 800-900g. The slurry is poured into a 2L rb flask mounted in a heating mantle. The upper part of the flask is clad in ceramic wool and the still head wrapped in an old thermal glove.

I'm afraid I have no temperatures to report as I have no thermometer pocket or ground glass thermometer. As the temperature is increased there is some awkward bubbling as the HNO3 makes it way through the slurry and the atmosphere initially becomes very dark red with NOx. After a while, the colour clears and the nitric acid comes over steadily (2-3 drops per second). The result is usually about 320mL of orange HNO3, density 1.57(2)g/cm3.

This is all very common knowledge but I feel it is important to include a full guide to what I do. The important bit is the purification step:

The contaminated HNO3 is placed in a 500mL pyrex jug on a hotplate/stirrer with stir bar. The output of a small fish tank air pump (capacity 0.75L/min) is led to the bottom of a small glass vial (tincture of iodine bottle, 100mL) via a silicone tube and glass tube. The vial is filled with CaCl2 and a length of output tubing is placed at the top of the vial, the whole array sealed with blu-tac. The output tube is connected to a length of glass tubing (which happens to have a capillary end) mounted in the acid. A thermometer is clamped in place and the temperature is brought up to 40-45C with stirring, and air being bubbled through, (temperature according to Microtek's work).

After about 3 to 4 hours of bubbling, and much off-gassing, the nitric acid is almost colourless, a slight yellow remains. Left to cool, this becomes absolutely colourless at room temperature. Density was calculated from the mass of 100mL of this acid to be 1.52(7)g/cm3. No urea was used at any point to rid the acid of NOx, as per Microtek's suggestion in his quantitative report!

Now, the density suggests 100% HNO3 which will clearly not be the case. Possible reasons for this? The ever present errors in measurements, possibly a little remaining NOx raising density. I have a slight worry that some sulphuric acid may have been carried across. As I am being quite intensive with my production of HNO3 - using up as much H2SO4 as possible, the heated flask in the distillation becomes filled with a great, irregular mass of solid sulphates towards the end. My fear is that these allow local heating of the remaining H2SO4 to boiling temperature, which I know is very high, but still I am paranoid to some extent about it, now I have it in my mind.

I'm probably just worrying about nothing, and I'm sure someone will set me straight. Besides, even if this were the case the acid could be re-distilled to leave the traces of H2SO4 behind, before removal of NOx.

Anyway, with a few concerns put aside: I have made highly concentrated nitric acid, free from NOx, with one distillation, no need for vacuum, no use of urea or DCM/dry ice extraction methods. I intend to improve the method with a stronger pump to power a glass gas diffuser, working in a multiple necked flask with reflux condenser to process larger volumes faster and capture escaping HNO3 vapor.

penguin6636
January 6th, 2008, 06:09 PM
The first time I distilled nitric acid I had placed a fan at the base of my condenser to blow away all the NO2 that was fuming in the air. It also kept my end product clear. I tried the same concept with a batch I just made and dripped it through a separatory funnel about 6 times. My initial product had a strong yellow color to it, but after dripping it past the fan several times it cleared up. I did this outside so the temperature was 5-10°C and the air was fairly dry. The amount of acid that evaporated was negligible. Does this method sound practical?

http://img201.imageshack.us/img201/2292/nitricno2dc9.jpg http://img201.imageshack.us/img201/4662/nitricclearun7.jpg

DetaDude
March 19th, 2008, 02:56 PM
I recently found myself browsing through a used book store and ran across an old publication, circa 1923 published in the U.K. "Absorption of Nitrous Gases"
by H.W.Webb MS, F.I.C.. This book is just full of helpful info on our favorite acid
and ways to make, concentrate, and purify it along with pit falls (allbeit aimed at an industrial operation) but adaptable to small scale.

One item that this book mentions is the use of ozone for purification and concentration of the acid by use of ozone. It does state that it is to expensive to use in industrial settings but performed well during experimentation (1923).

I have long been intrested in using ozone in conjunction with HNO3 production and after reading this publication I think I'll tinker around with it in my lab. If
anyone out there has some info or background they don't mind sharing I would be deeply appreciative. As soon as I can set up some tests I'll report back on my findings.

I realize that this is long out of publication but poss. may find an old copy in a school/public library, used book store etc.