Sciencemadness Discussion Board
Not logged in [Login - Register]
Go To Bottom

Printable Version  
Author: Subject: Nitric Acid Purification
VSEPR_VOID
International Hazard
*****




Posts: 656
Registered: 1-9-2017
Member Is Offline

Mood: Fullerenes

[*] posted on 28-4-2018 at 18:12
Nitric Acid Purification


I have prepared ~500 ml of by the distillation of a mixture of potassium nitrate and sulfuric acid. This acid was then made clear by bubbling dried air through it. Density shows it to be between 68% and 70% pure.

RDX is on my 'chemical bucket list' due to its importance as a high explosive and extreme stability (not even detonating under stall arms fire). I also already have purified Hexamethylenetetramine set aside just for this purpose. All the procedures I have seen for its synthesis call for white fuming (WF) nitric acid having a concentration of about 98%.

WF nitric acid in "Handbook of Preparative Inorganic Chemistry" is prepared using phosphorus pentoxide as a drying agent along with vacuum distillation.

I. Acid of the highest possible concentration
is distilled; then an inert,
dust-free gas stream, preferably
preheated, is passed through toremove
the nitrogen oxides. It is ultimately
distilled over P2O5.

II. By distillation with H3SO4. The
starting material is acid of the
highest possible concentration...The apparatus
is connected to an aspirator
via a safety trap.
It is also recommended that a stream of oxygen containing some
ozone be passed through the highly concentrated acid and that it be
distilled under aspirator vacuum.

I lack both phosphorus pentoxide and a vacuum distillation apparatus sadly and can not produce it by this method. Does anyone have a procedure for preparing WF nitric acid without the equitment/reagents listed above? Many thanks.




Bane: It would be extremely painful…

CIA Agent: You’re a big guy.

Bane: … for you.
View user's profile View All Posts By User
ninhydric1
National Hazard
****




Posts: 339
Registered: 21-4-2017
Location: Western US
Member Is Offline

Mood: Bleached

[*] posted on 28-4-2018 at 19:00


You don't need a vacuum distillation apparatus. If you have 90+% sulfuric acid, you can just react it with a nitrate salt and distill carefully at 83 degrees Celsius to prevent nitric acid decomposition. This will produce fuming nitric acid as long as you don't add water to the original reaction mixture.

NileRed did it without a vacuum:
https://www.youtube.com/watch?v=8YWVBBGSxZ8




The philosophy of one century is the common sense of the next.
View user's profile View All Posts By User
NeonPulse
National Hazard
****




Posts: 413
Registered: 29-6-2013
Location: The other end of the internet.
Member Is Offline

Mood: Everclear or Neverclear. Can't decide.

[*] posted on 28-4-2018 at 19:59


The problem is without a vacuum you will get NO2 contamination so this just adds the extra step of blowing dry air through it a second time. I found that even much over the temp requirement for distillation will create at least some decomposition. Distilled from P2O5 will create some N2O5 which is also a potent nitration agent but if you only want HNO3 then a second distillation over H2SO4 after the initial run will concentrate the acid sufficiently to be useful in RDX and other things. If you started from HDN then the acid required can be less than 98% concentration and you will still get decent yield.



Where there is a will
there is a way.

AllCheMystery!
https://www.youtube.com/channel/UCWbbidIY4v57uczsl0Fgv7w?vie...
View user's profile View All Posts By User
Vosoryx
National Hazard
****




Posts: 253
Registered: 18-6-2017
Location: British Columbia, Canada
Member Is Offline

Mood: Afraid of HCN

[*] posted on 28-4-2018 at 20:29


I've heard from various sources that (carefully) mixing azeotropic nitric acid with azeotropic sulphuric acid and then distilling at 83 degrees will, if repeated a few times and done on an arid day, produce WFNA. (Once the dissolved gasses are boiled out) This works even better if you start from Azeotropic sulphuric (instead of just straight 92% drain cleaner, which is what I start from for my nitric) and dry the nitrate salt beforehand.




Anime is trash and so am I
View user's profile View All Posts By User
VSEPR_VOID
International Hazard
*****




Posts: 656
Registered: 1-9-2017
Member Is Offline

Mood: Fullerenes

[*] posted on 28-4-2018 at 20:39


I have heard there is a method that involves urea. Is there a method that does not involve distillation?



Bane: It would be extremely painful…

CIA Agent: You’re a big guy.

Bane: … for you.
View user's profile View All Posts By User
Sulaiman
International Hazard
*****




Posts: 2234
Registered: 8-2-2015
Location: Walsall, England
Member Is Offline


[*] posted on 29-4-2018 at 00:25
Why purify in this case ?


Why would you not use azeptropic HNO3 with dissolved NO2 for nitration.
Or RFNA instead of WFNA ?
What problem would the dissolved NOx cause ?




CAUTION : Hobby Chemist, not Professional or even Amateur
View user's profile View All Posts By User
VSEPR_VOID
International Hazard
*****




Posts: 656
Registered: 1-9-2017
Member Is Offline

Mood: Fullerenes

[*] posted on 29-4-2018 at 00:34


The synthesis of RDX requires WF nitric acid in all of the methods I have seen so RF nitric acid or azotropic nitric acid will not due. If I can not find a way to make it without distillation I will have to ask someone on the forum to make it for me and send it to me.



Bane: It would be extremely painful…

CIA Agent: You’re a big guy.

Bane: … for you.
View user's profile View All Posts By User
Fulmen
International Hazard
*****




Posts: 1202
Registered: 24-9-2005
Member Is Offline

Mood: Bored

[*] posted on 29-4-2018 at 01:22


Quote: Originally posted by Vosoryx  
azeotropic nitric acid with azeotropic sulphuric acid and then distilling ... produce WFNA


Correct. This is called extractive distillation, the optimal ratio seems to be equal volumes of 67% nitric and 98% sulfuric acid. With weaker acids you should calculate the amounts so that you end up with the same concentration sulfuric acid after distillation. The FNA produced will be appr. half the volume of the initial NA.
The product will be somewhat contaminated with NOx unless distilled under vacuum, but IIRC a small amount of urea will remove this. I can't recall if I did this or not, but it did produce RDX in good yield by direct nitration of hexamine.

The only other method for making FNA I can recall that doesn't use distillation is to react anhydrous calcium nitrate with conc. sulfuric acid. The problem is that you end up with a gypsum paste saturated with FNA, and separating would a PITA to put it mildly. I've only tried it once and ended up dumping the entire batch.
It might be possible to wash out the NA using excess SA to produce a mixed acid for other nitration reactions though.




We're not banging rocks together here. We know how to put a man back together.
View user's profile View All Posts By User
XeonTheMGPony
International Hazard
*****




Posts: 1088
Registered: 5-1-2016
Member Is Online

Mood: No Mood

[*] posted on 29-4-2018 at 05:44


there was one methode for producing pure nitric by reacting nitrate salt with sulfuric acid, then adding small amount of water then extracting with DCM
View user's profile View All Posts By User
Deathunter88
National Hazard
****




Posts: 356
Registered: 20-2-2015
Location: Beijing, China
Member Is Offline

Mood: No Mood

[*] posted on 29-4-2018 at 09:17


WFNA can easily be made by doing a solvent extraction of 68% (or lower concentration as well) nitric acid with dichloromethane. Nitric acid is very soluble in DCM, but water is not. I don't have the exact procedure handy but I do remember there being a SM thread on it, and following the procedure i successfully produced 5ml of WFNA as a proof of concept. It's really just like any other solvent extraction. Additionally, if you are willing to evaporate off the DCM instead of distilling it, you don't even need to distill anything.

Apologies I didn't see XeonTheMGPony post, but I hope mine will still give this procedure some credibility for just how easy it is.

[Edited on 29-4-2018 by Deathunter88]
View user's profile View All Posts By User
VSEPR_VOID
International Hazard
*****




Posts: 656
Registered: 1-9-2017
Member Is Offline

Mood: Fullerenes

[*] posted on 29-4-2018 at 13:33


That might work! I will have to look into it and purchase some DCM



Bane: It would be extremely painful…

CIA Agent: You’re a big guy.

Bane: … for you.
View user's profile View All Posts By User

  Go To Top