Sciencemadness Discussion Board

Differing Effects of Red vs. White HNO3 in a Nitration

ADP - 11-4-2005 at 19:24

I was working with some HNO3 today and am preparing some for a nitration synth, which will happen sometime this week, but if one were to use red HNO3, how will this effect the final product vs. if one uses white HNO3? Let's assume the synthesis was that of nitroglycerin

This is assuming both are 98% fuming. I know the only difference is that red has higher amounts of NO2 dissolved in it.

[Edited on 12-4-2005 by ADP]

cyclonite4 - 12-4-2005 at 01:03

Red nitric acid is just nitric acid with a certain amount of nitrous acid contaminating it. From what I've heard it can be fixed by heating (to decompose the nitrous acid to nitric acid and NO) or bubbling air through it (to oxidise HNO2 to HNO3).

I assume that if any effects were caused by using red nitric, it would be because of the nitrous acid contaminating it. However, I'm no authority on nitration.

[Edited on 12-4-2005 by cyclonite4]

Esplosivo - 12-4-2005 at 02:37

I think that the red colour is more likely due to dissolved NO2 in the mixture other than nitrous acid. Nitrous acid is unstable, it decomposes readily at rtp, and besides it has a light bluish colour not red. Bubbling dry air through the acid will probably remove most of the 'impurities'.

Btw, I'm not sure if discussion on synthesis of explosives such as nitroglycerine is allowed. Next time try be more discreet and only mention 'nitration' and leave out the nitroglycerine part. I suppose that should be better, but I am no admin. The final word is that of The bird :P

Blaster - 12-4-2005 at 02:50

With the NG for the homemage Gelignite I made for the underwater explosives post I just used ordinary conc HNO3 (70%) with an equal vol of conc H2SO4 (98%). Its a myth that fuming nitric acid ie. 98-100% is needed! The yield may be slightly lower I suppose.

cyclonite4 - 12-4-2005 at 02:55

As far as I am aware, the synthesis of explosives is allowed here, just not discussion of practical uses. ;)

ADP - 12-4-2005 at 11:43

So if I proceded to bubble air through tubing into the red fuming acid, the result should be white fuming acid?

I know that the only difference is the dissolved NO2 which gives it its color of slightly yellow. I'll give it a try and by the way I corrected my original post into a more scimad correct post. Thanks :P

chemoleo - 12-4-2005 at 11:57

The usual way to remove free NO2 from HNO3 is to add the necessary quantity of urea, which is converted then to N2 and CO2.
This turns it into the 'white' form, and this is normally done at very high concentrations, i.e. 98% or so, at lower conc. one just gets urea nitrate afaik.
The best way to get rid of most NO2 is to simply distill the HNO3 carefully in the first place. The first initial fractions are discarded (not used), and so are the last, for they contain lots of NO2.
Another is to keep the conc. HNO3 in the dark & cool, it decomposes slowly at light exposure. This becomes really bad when sun light (UV) is exposed to it, as noticed when the destillation was done outside on a sunny day.

Why is red HNO3 so bad? Because it tends to oxidise rather simply nitrate (esterify), so runaways are more likely, which don't serve the purpose of the reaction.

As to board policy - it's quite simple really.
Discussion of 'how can I use AP best to blow up AN in my sand pit' is not what this forum is about. However, discussion of 'I reacted x with y, which supposedly forms compound z (ref 1), which formed a yellow substance that deflagrated confirming its identity' is more along the lines of what is desired here. It's not the 'act' of blowing things up (which is discussed to death elsewhere), it's about 'how do I get there' and 'does it really work' by showing with an experiment that it does. That is essentially what is meant by practical applications - to prove a point they are fine, but to make this the sole purpose of your endeavours is not what is desired here (at least in terms of discussion subjects). Now back on topic :).

[Edited on 12-4-2005 by chemoleo]

Rosco Bodine - 12-4-2005 at 12:21

Actually , urea nitrate is the material
which reacts with the NO2 , and urea nitrate is added directly to nitration mixtures , sometimes mixed with the hexamine dinitrate or pentaerythritol as a small percentage , less than 1 percent ,
as a " stabilizer " to react with and neutralize any NO2 produced during the course of the nitration . Safety and yields are increased by using urea nitrate in this manner , even when relatively white and pure nitric acid is there at the start of the
nitration .

Now there are some nitrations where it is believed that the NO2 impurity is actually the active nitration agent , and is essential to be present in the nitration mixture , being replenished by decomposition of the nitric acid as the nitration proceeds . Picric Acid is believed to be formed via this route . In fact experiments have shown that some nitrations will not proceed at all if the
nitric acid is purified to a point of being completely free of NO2 , which supports the theory that the nitrating agent for some compounds indeed is the very NO2 which is problematic in nitrations of different compounds .

ADP - 12-4-2005 at 14:11

Wow guys thats some great info thanks a ton, I'll do a little research on it. The problem with distilling white nitric is the fact that it must be done around 60*C which means for a very slow distillation process.

Red can be done much quicker and therefore since I know now that the NO2 in it can be removed, I realize one might want to take that path, but thanks for the info.

ADP - 13-4-2005 at 12:21

Can HNO3 undergo thermal decompostion? I know that light has an effect on it but say one heated HNO3 up to high temperatures, without light would it thermally decompose?

Joeychemist - 13-4-2005 at 15:18

HNO3 undergoes partial decomposition at its boiling point (about 86 C), higher temperatures will cause it to decompose faster and at about 256 C decomposition is complete.

ADP - 13-4-2005 at 18:43

So this is why one would want to distill at the lowest possible temp... It would decomp into H2O and NO2 I'm sure. Thanks for the info.

Mahlzahn - 20-4-2005 at 06:23

Destillations temperatures of
dilute HNO3 < 121 degree celsius
normal fuming HNO3 < 82 gegree celsius

fuming white HNO3 < 80 %
fuming red HNO3 ;) < 95 %

fuming red HNO3 ;) < 98 %
containing up to20% NO2, not good useful for normal nitration. (HNO3 oil)

A little bit of NO2 in the white HNO3 are not of interest. (slight yellow)

Using a bit more H2SO4, the fuming white
HNO3 80-90% are good useful.

Using normal fuming red HNO3 <95% for nitration which the presence of H2O are not good for the synthesis.

Concentration of the acid can be calculated when measuring the desity
of the acid.

[Edited on 21-4-2005 by Mahlzahn]

my nootloss - 2-6-2005 at 20:14

In all of my experience (mind you that it’s limited) the nitric acid was all most neon yellow, and only the purest of chemicals where used. Any idea as to why this was?

Joeychemist - 2-6-2005 at 21:28

I would assume that your HNO3 had decomposed a little while you were distilling it over and some NO2 was produced and consequently was dissolved into your HNO3, this would make your acid yellow for sure! A little NO2 is ok for most procedures, but sometimes it can have an adverse affect and can lead to runaway nitrations in some reactions.

If you want to get rid of the NO2 and with it the yellow color, try dissolving a little Urea in the acid and bubbling air through it, that should fix the problem right up!

my nootloss - 3-6-2005 at 05:53

Originally posted by Joeychemist
If you want to get rid of the NO2 and with it the yellow color, try dissolving a little Urea in the acid and bubbling air through it, that should fix the problem right up!

Yeah thanks, is the urea from pee ok to use? And what’s the purity of that urea?

chemoleo - 3-6-2005 at 06:05

Errr... I hope this is a joke.

No it is NOT ok to use!

cyclonite4 - 3-6-2005 at 06:51

Pissing into nitric acid :D

I'd suggest buying urea (its used as a fertiliser, especially in places where NH4NO3 is regulated), however I've heard that some places dont have it, so if you want to use "natrual urea sources" read up on chemoleo's extraction process, this also informs you of the impurities in 'pee'. :)

ADP - 3-6-2005 at 06:55

If I added the urea wouldn't it convert to urea nitrate and then react with NO2? or would the urea itself react with the NO2 because it seems like the Urea would be converted to urea nitrate.