Sciencemadness Discussion Board

ammonium nitrate purification

Stanfield - 19-11-2003 at 04:17

Hi !
I usually buy my ammonium nitrate in a garden store and so, it's a fertilizer grade full of impurities like anti waking agents, sodium bicarbonate and so.

I've found a french text on google on how to purify it, here it is :

"dissolve the fertilizer in hot methanol and filter the solution. By mixing the solution with an equal volume of unleaded gasoline, the ammonium nitrate will instantly cristalize."

sorry for mistakes :)

But I've 2 problems :
- I don't know the solubility table on NH4NO3 in hot methanol
- Methanol is relatively expensive...

so, here is my question : is there a way to replace the methanol with another product ? will ethanol work too ?

thanx a lot !

EDIT : and what was supposed to do ? I've search both E&W, here, even on google and patents. I've found nothing about the purification of ammonium nitrate...
I've thought, here, some people could have helped me !

is it a crime to ask ?

[Edited on 19-11-2003 by Stanfield]

vulture - 19-11-2003 at 06:18

Are you the stanfield from the E&W forum? In that case you should have known better than to post such a question.


Polverone - 20-11-2003 at 04:21

Solubilities of Various Alkali Metal and Alkaline Earth Metal Compounds in Methanol
Stenger, V. A.;
J. Chem. Eng. Data; (Article); 1996; 41(5); 1111-1113.

20.2 g NH4NO3 per 100 g methanol at 30 degrees C. There are values for other temperatures too, but solubility doesn't seem to vary rapidly.

I can't find solubility data for NH4NO3 in ethanol. This is interesting enough to leave the topic open. Stanfield is actually asking about specific methods rather than leaving the question open-ended. If there are really sodium compounds in there then he can't just dissolve in water and filter.

Al Koholic - 20-11-2003 at 06:54

Yeah I think so...

I replied to this on E&W but haven't checked up on it. Now that I know you desire to purify AN, I am left wondering why you wouldn't just recrystallize it from water as it definetly has a solubility differeential over temp in that...

vulture - 20-11-2003 at 08:13

Hmm, I thought he was referring to the classical CaCO3/NH4NO3 fertilizer.

I've never seen any NH4NO3 fertilizer with considerable amounts of sodium in it.

Now that I think of it, sodiumhydrogencarbonate shouldn't be a problem in NH4NO3 solution:

NH4+ + HCO3- ----> NH3 + H2O + CO2

EDIT: Aren't ionic sodium compounds also soluble in methanol?

[Edited on 20-11-2003 by vulture]

Stanfield - 20-11-2003 at 08:38

A friend of mine said me I can't make ANFO or ANNM with pure ammonium nitrate. He told me if I buy NH4NO3 as a fertilizer grade I'll have to purify it.

If I dissolve it in hot water, I'll dissolve anti caking agent and all these other stuff, no ?

But, If someone suceed purifying it that way and detonated it, this is what I want !

thanx anyway.

Al Koholic - 20-11-2003 at 13:58

Just dissolve it in boiling will dissolve anything ionic. Filter it while really hot to remove insolubles then let it cool and collect the AN.

If you want reallllllly pure stuff, do a couple more recrystallizations to get out any remaining impurities.

And NO! You do not need pure AN to make ANFO or ANNM. Believe me I have detonated enough ANFO full of sticks, sawdust, plastic chunks, and miscellaneous crap to know.

Stanfield - 20-11-2003 at 18:51

really ? fertilizer grade ? fine !

My NH4NO3 is prills, do I need to grind it before dissolving it in hot water ? I guess it will dissolve easier that way, no ?

see ya !

Sir Dudalot - 17-3-2004 at 19:21

I tried to purify some fertilizer (16-0-0) by dissolving in hot water, filtering out impurities, then boiling it down some and chilling it. The process yielded what I thought to be pure ammonium nitrate but I'm starting to doubt that now. I tried to nitrate with it and plenty of HNO3 fumes started coming from the solution when I put it in sulfuric acid but a good portion wouldn't dissolve. The part that wouldn't dissolve was around 1/3 of the total mass that I added to the sulfuric acid. I thought that maybe some was just having problems dissolving because it was clumping badly and added the erythritol anyway. The yield was exactly zero, and I mean zero. I've read where a few people would dissolve in water, filter, and recrystalize with no problem and I can't see where I could screw up such a simple procedure. Are there any other definitive properties of ammonium nitrate that could be used to seperate it from this other stuff that dissolves in water?

This topic is kind of old but I really didn't want to start a new thread on something so simple...

Mendeleev - 17-3-2004 at 20:43

Curious thought, if you tried to distill nitric acid from common fertilizer grade ammonium nitrate which contained salts such as sodium bicarbonate and sodium chloride, would your nitric acid be contaminated with hydrochloric acid, as it boils at a lower temperature than nitric? Also, why all the hostility to E&W members? I am myself a member of E&W under the same name.

[Edited on 18-3-2004 by Mendeleev]

Esplosivo - 18-3-2004 at 09:36

If the fertilizer does contain NaCl, it will react with conc. Sulphuric acid to liberated HCl fumes. These will surely contaminate the nitric acid produced.

Sir Dudalot, just try using some other source of ammonium nitrate, like cold packs, or an other brand of fertilizer containing ammonium nitrate. It occured to me once that the 'ammonium nitrate fertilizer' contained a mixture of ammonium sulphate, NaCl, Ca(NO3)2, and other impurities. Before buying the fertilizer check the composition of the mixture. It is generally around 93% ammonium nitrate, with the rest being inert material.

Mendeleev - 18-3-2004 at 18:45

About the cold packs and such, the whole point of most of us, or at least me being interested in fertilizer is that it is cheap. Almost all my chemicals come from Home Depot, Lowes, or ACE and the rest I synthesize myself, and for nitric acid, I have plenty of >98% potassium nitrate bottles for $4 per 450g standing on the shelf at my local Lowes by far not a bad price, but the Ammonium Nitrate fertilier is about $6 for 25 kg, which would significantly reduce costs as I do many nitrations. However if ammoniun nitrate is bought in cold packs that would most likely cost at least as much as the potassium nitrate if not more.

Esplosivo - 18-3-2004 at 23:14

Well regarding purity, it is probably best to use KNO3, which would yield better results.

Sir Dudalot seperation of ammonium nitrate is as easy as you mentioned. The ammonium nitrate being highly soluble in water will seperate from the other substances. Try reducing the amount of water used or else reduce the temperature. Don't use boiling hot water. Try get the temperature of the water to 50 deg. or so. This will reduce the yield but it will avoid some substances with a low solubilty to dissolve.

Ammonium nitrate dissolves 118g/100g water @ 0C therefore reducing the temperature will still dissolve much of the nitrate.

IgnorantlyIntelligent - 22-3-2004 at 17:46

I buy my AN in 40lbs bags for 12 bucks. I disolve it in water, filter the water, and poor it into a big bucket. About a day later the AN crystals apear and I pluck em out. Saves a ton of money.

Sir Dudalot - 22-3-2004 at 18:12

This just came in a little package (5 lb). I'm going to go out and buy a big 20 kg package pretty soon. It's 34-0-0 so hopefully I'll have better results with it. If not I'll just stick to cold packs like I've been using. They're prilled though which comes in handy sometimes if you're looking for a nice low density...

Sir Dudalot - 29-3-2004 at 14:32

Ah, the questions just come rolling in. I was going to buy the 34-0-0 when I spotted a bag of 37-0-0 so naturally I got that one. I went through purification steps and added it to my H2SO4, all of it dissolved. However, it fizzed a bunch after dissolving and doesn't anymore. The mixture seems thicker than the normal NH4NO3+H2SO4 mixture. I've read the 47-0-0 is urea, could I have just bought a 50lb. sack of urea?

I should also add that no nitric acid fumes are coming off of it but if I stick my nose (literally) in the beaker I can barely detect them.

[Edited on 3-30-2004 by Sir Dudalot]

Mendeleev - 29-3-2004 at 21:51

There's a good chance you probably bought some sort of fertilizer "alloy". It probably contains ammoniun nitrate, as well as a lot of other crap, probably calcium and sulphate compounds.