Sciencemadness Discussion Board

Ammonium nitrate/ Ammonium sulphate

ill behaviour - 20-8-2016 at 21:24

I am wondering if anyone could make a suggestion to my problem.
These days pure ammonium nitrate fertilizer is very hard to obtain
as many of us know.
The closest thing OTC in my town is a fertilizer combination of
ammonium nitrate 45% mixed with ammonium sulphate 55%
So my plan was to find a solvent that would dissolve the AN
and let me filter off the AS then evaporate the solvent away for AN. Its didnt work that way. Ammonium sulphate is not soluble in acetone or methanol according to the information I could find.
I used hot methanol but something is not right.
I have tried twice now and both times For every 150 grams of mixed fertilizer I got back 5 grams of crystals, plus I wasted lots of time.

RocksInHead - 20-8-2016 at 22:36

What are you going to use the Ammonium Nitrate for? If you are using it for HNO3 production than the Ammonium Sulphate won't matter, since it is a byproduct of the reaction anyway, you will just have to adjust for the weight of the Ammonium Sulphate contamination.

Even if you don't need it for HNO3, you could still make it and then react it with another Ammonium compound to yield pretty high purity Ammonium Nitrate.

j_sum1 - 20-8-2016 at 22:59

If you must have ammonium nitrate then you might be able to get hold of some calcium nitrate. A solution of Ca(NO3)2 added to a solution of your ammonium sulfate/nitrate mix wi precipitate calcium sulfate and leave you with a solution of straight AN. You would need to work out your stoichiometry of course.

ill behaviour - 21-8-2016 at 14:26

Thank you for the reply.
I can get calcium nitrate so I am pleased to have another route.
Before I try that I am going to slightly modify what I have already tried.
Because the methanol really didnt work effectively I am going to try
and dissolve the nitrate/sulphate in water then add the methanol and see if
that works any better.

Dr.Bob - 21-8-2016 at 14:50

Dissolving AN in an organic solvent is asking for trouble, as you have an oxidant and fuel mixed and heated. Not likely to go off, but if it catches fire it could quickly get out of hand.

I would look at water based systems, or other methods. Even just using a sieve might work in some cases, as I have seen fertilizer with different particle sizes. That won't get it completely pure, but if you can get it partly separated, then the purification will be easier.

If you look around, you might be able to find some other sources, but it is getting much harder to find pure AN these days.

XeonTheMGPony - 21-8-2016 at 16:16

Cold packs ordered from medical suppliers are usually pure ammonium nitrate prills

ill behaviour - 22-8-2016 at 08:48

Making some progress.
After attempting to extract the AS by adding methanol to the AN/AS water solution
I found that it would work some of the time.
I start with 10 grams of AN/AS fertilizer which I crush into dust then slowly dissolve
in the minimum amount of water then add the methanol. I know that 5.5 grams of
AS is required for a pure AN/water solution. I tried 3 times and for whatever reason
I could not get repeatable result.
Anyhow after reading liquid-liquid extraction on wiki I realize I have been using
incorrect procedure.
This time the AN/AS water solution was slowly added with stirring to methanol.
Wonderful results. The AS is not dry so I cant say if I removed 100% but its close.
I then added the mostly AS free solution to more methanol and only tiny bit more
AS was recovered.
I am going to try using acetone as it will be much easier to evaporate off, its more
expensive but the time saving makes it worth it.