Sciencemadness Discussion Board

Ammonium Nitrate Purity?

Brightthermite - 5-7-2020 at 12:19

I recently purchased 5 lbs of "DIY Cold Pack Refills" (clever branding :D), the intended purpose is definitely for exploding targets. Since you do not necessarily need very pure AN for this it makes me question its purity. I have got poor yields doing various nitration but there were too many factors to peg down the AN as the problem. The cold pack AN is in prilled form, smooth almost looks like a cream colored plastic. It does not resemble the AN fertilizer which is bright white and almost translucent.

Does anyone have any ideas on how to test its purity? I would like to avoid a re-crys and keep it in prilled form.

Belowzero - 5-7-2020 at 23:19

Perhaps crude; AN does not leave any residue when thermally destroyed.
If you have an accurate scale you can measure the weight after it is decomposed.
Otherwise a melting point determination can give you some idea.




[Edited on 7-7-2020 by Belowzero]

Mateo_swe - 6-7-2020 at 12:41

Try melting point, AN should melt at 169.6 °C.
You could try measuring the volume and weight of a sample and compare with AN density 1.725 g/cm3 (20 °C).
Its a little tricky measuring the volume though.

monolithic - 9-7-2020 at 07:33

Did you order this on Amazon? I just did the same, hope the purity can be improved through recrystallization from methanol.

Somewhat on-topic, what happened to AN based fertilizers? All I see is urea and other non-AN blends. I understand it's restricted due to Oklahoma City, plant explosion in Texas, etc., but it seems like manufacture of it has completely stopped.

Ammonium Nitrate Fertilizer

MadHatter - 9-7-2020 at 07:54

In terms of available nitrogen urea is
superior to ammonium nitrate. Urea
contains over 46% nitrogen versus
35% from ammonium nitrate. This
pyro supplier for example:

www.fireworkscookbook.com

carry the agricultural prills for $1
LB. Minimum 10 LB order. I've ordered
from them a couple of times. They're
very good as pyro suppliers.

Brightthermite - 9-7-2020 at 18:40

Quote: Originally posted by monolithic  
Did you order this on Amazon? I just did the same, hope the purity can be improved through recrystallization from methanol.

Somewhat on-topic, what happened to AN based fertilizers? All I see is urea and other non-AN blends. I understand it's restricted due to Oklahoma City, plant explosion in Texas, etc., but it seems like manufacture of it has completely stopped.


Yes it was from amazon so Im sure we ordered from the same seller. I re-cyst with water, it was full of dust and dirt but it looks to be pretty pure.

Im not for sure what happened to the fertilizer, sometimes you can buy it at my local co-op. I live in a backwoodsy area though. Is it cheaper to manufacture than Urea?

monolithic - 22-7-2020 at 12:51

As a follow up, the AN was recrystallized from water. Basic procedure was to mix 5 pounds of AN with 2000 ml room temperature water and sit overnight. None of the impurities settled to the bottom, unfortunately. Vacuum filtered the ~4000 ml solution on a fritted filter to yield a light yellow solution, and then vacuum filtered this solution again on a fine filter paper. The solution was then boiled down and precipitate was collected.

https://i.imgur.com/bHYXjRw.jpg
https://i.imgur.com/5iyn1qq.jpg
https://i.imgur.com/1wgM8z2.jpg
https://i.imgur.com/IEl2nNR.jpg

It's a huge pain in the ass, took 2 or 3 days of boiling with 2000 ml beaker and a good lab hot plate. Some tips:
1. Don't use fritted glass for initial filtering, use coarse filter paper. The red stuff is slimy, poorly soluble in water, and plugs/stains frits. I have no idea what it is. It's poorly soluble in hot water, acetone, hydrochloric acid, sulfuric acid, and isopropyl alcohol.
2. When boiling down don't reduce volume by any more than 25-33%. If you go past this a shit ton of ammonium nitrate will crash out and form a solid block and trap the impurities. Water isn't an ideal solvent for this recrystallization but it does work. Toward the end I would boil down 25% at most and then rely on freeze precipitation. The last crop of crystals (before I lost patience) held on to some of the yellow impurity so I recrystallized again from fresh water.
3. Consider using a gas burner or a high power induction hot plate in a metal container. Bringing 2 liters of solution to boil takes forever, even with aluminum foil.

I recovered about 4 pounds of the initial 5 pounds. The remaining 1 pound could probably be recovered but I don't have the patience. The product is a bit wet so the plan is to dry in an oven at 80-90 C. AN does sublimate and eventually decompose as a white gas (nitrous oxide + water vapor.) This should not be an issue at 80-90 C. In its molten state it is as sensitive to impact as TNT, so probably best to avoid that. See https://apps.dtic.mil/dtic/tr/fulltext/u2/655888.pdf page 7/48 of the PDF.

[Edited on 7-22-2020 by monolithic]

Brightthermite - 22-7-2020 at 19:51


2. When boiling down don't reduce volume by any more than 25-33%. If you go past this a shit ton of ammonium nitrate will crash out and form a solid block and trap the impurities. Water isn't an ideal solvent for this recrystallization but it does work. Toward the end I would boil down 25% at most and then rely on freeze precipitation. The last crop of crystals (before I

[Edited on 7-22-2020 by monolithic][/rquote]

Freeze precipitation it what I found to work best after a lot of struggling. I would boil the solution down to much and the second it came in to contact with anything that was of a slightly cooler temp, the AN immediately caked on in a hot sludge.

Please keep me updated on the drying, I am having a very hard time oven drying and keep moister out if it in general (around 80% humidity constantly).

monolithic - 23-7-2020 at 15:19

Quote: Originally posted by Brightthermite  

Freeze precipitation it what I found to work best after a lot of struggling. I would boil the solution down to much and the second it came in to contact with anything that was of a slightly cooler temp, the AN immediately caked on in a hot sludge.

Please keep me updated on the drying, I am having a very hard time oven drying and keep moister out if it in general (around 80% humidity constantly).


The AN was split into two batches and spread in a glass baking pan. The pan was heated to 70-90 C (kind of varied) in a conventional oven, the door propped slightly open with a spoon to promote airflow. Every 30-60 minutes AN was stirred/scraped. Total drying time was about 10 hours, to constant mass. All AN was passed through a kitchen sieve and the remaining pieces were ground with a mortar and pestle until they would pass through a sieve. Total mass was about 3.5 pounds of free flowing, snow white AN which was stored in an ordinary ziploc. I guess the filtrate should have been boiled down a bit more, oh well.

https://i.imgur.com/G8FMXrf.jpg

Mortar and pestle definitely sucks but I don't have the balls to use a coffee grinder or a food processor. Maybe with a 100 foot extension cord. :o

Brightthermite - 24-7-2020 at 08:40

Quote: Originally posted by monolithic  
Quote: Originally posted by Brightthermite  

Freeze precipitation it what I found to work best after a lot of struggling. I would boil the solution down to much and the second it came in to contact with anything that was of a slightly cooler temp, the AN immediately caked on in a hot sludge.

Please keep me updated on the drying, I am having a very hard time oven drying and keep moister out if it in general (around 80% humidity constantly).


The AN was split into two batches and spread in a glass baking pan. The pan was heated to 70-90 C (kind of varied) in a conventional oven, the door propped slightly open with a spoon to promote airflow. Every 30-60 minutes AN was stirred/scraped. Total drying time was about 10 hours, to constant mass. All AN was passed through a kitchen sieve and the remaining pieces were ground with a mortar and pestle until they would pass through a sieve. Total mass was about 3.5 pounds of free flowing, snow white AN which was stored in an ordinary ziploc. I guess the filtrate should have been boiled down a bit more, oh well.

https://i.imgur.com/G8FMXrf.jpg

Mortar and pestle definitely sucks but I don't have the balls to use a coffee grinder or a food processor. Maybe with a 100 foot extension cord. :o


I believe you would be okay to use a machine to process the AN as long as it was clean. While drying in the oven did your AN redissolve into a sludge? If so was your final dry product one chunk or a crumbly mass?

monolithic - 24-7-2020 at 12:16

Quote: Originally posted by Brightthermite  
I believe you would be okay to use a machine to process the AN as long as it was clean. While drying in the oven did your AN redissolve into a sludge? If so was your final dry product one chunk or a crumbly mass?


The first batch was pretty dry to begin with and so the oven drying went smoothly. The second batch was damper and I was concerned about a sludge forming or it solidifying into a large slab. It was stirred/agitated every 30-60 minutes with a chemistry microspatula -- scrape the side and bottom of the baking pan until you feel smooth glass, stir around the crystal mass, and break up the larger damp aggregates that might form by pressing on them with the spatula. Overall it wasn't very difficult, just time consuming. If it's really damp, like sopping wet, I would recommend additional vacuum filtration before putting it in the oven. Combining both batches, I would say about 1/2 of the volume of product passed through the sieve in the first try, 1/4 was worked over with a mortar and pestle without too much difficulty before passing through the sieve, and 1/4 was repeatedly smashed and ground in the mortar and pestle with some difficulty before it would pass through the sieve.

For what it's worth, I just checked the ziploc bag and the AN is still dry and free flowing after about 24 hours. Again this is just oven drying to constant mass and storing in an ordinary ziploc bag with the excess air squeezed out. AN is hygroscopic but it's not like working with pyridine HCl or anything.

[Edited on 7-24-2020 by monolithic]

Fyndium - 10-1-2021 at 15:22

Has anyone got sol curve of AN in methanol or ethanol?

B(a)P - 10-1-2021 at 17:01

Not sure how reliable this is, but they are both here
https://en.crystalls.info/Solubility_curve

Fyndium - 11-1-2021 at 05:42

It appears to contain no other data than 17.1g, without temp info. I suppose the sol does not change that much upon heating?

How practical is it to recrystallize AN from water? It has somewhat extreme solubility, and being as much hygroscopic the point when AN dissolves in water or water dissolves in AN becomes quite unclear.

Belowzero - 11-1-2021 at 10:48

Quote: Originally posted by Fyndium  
It appears to contain no other data than 17.1g, without temp info. I suppose the sol does not change that much upon heating?

How practical is it to recrystallize AN from water? It has somewhat extreme solubility, and being as much hygroscopic the point when AN dissolves in water or water dissolves in AN becomes quite unclear.


Agreed a 1:1 solubility is called contamination :P

I've been doing this a lot and AN does crystalize from saturated solutions, it does however form quite large (and beautiful) needles which also trap impurities.
This can still be an improvement.

I've also experimented with water/ethanol mixtures which makes crystalization more rapid and in theory can leave more unwanted product in solution.

As with any crystalization the more fractions you do the worse it gets when it comes to purity.
The remainder can be crashed out of solution quite easily as demonstrated here:
https://www.youtube.com/watch?v=1xEMbNfofko

I would suggest purifying a fraction and use the rest as bulk for making HNO3 for example.

And of course if you have a lot of cheap sulfuric acid you can make very pure AN by distilling it in ammonia.



unionised - 11-1-2021 at 12:59

Quote: Originally posted by Brightthermite  


Does anyone have any ideas on how to test its purity?

Titration.

Fyndium - 11-1-2021 at 23:59

Quote: Originally posted by Belowzero  

https://www.youtube.com/watch?v=1xEMbNfofko


Funny how the most eager tubers always have the crappiest equipment.

And every. single. time. people use too small vessels.

It might be impossible to state what is mixed in a fertilizer, or is it water soluble or non-water soluble. Filtering will get rid of those, but the remaining liquor might still be far from pure. Although, depending on the use, it might be very well doable.

Funny how one product contains many % of potassium chloride in it, just like it was placed there to ruin sulfuric acid extraction. On the other hand, it should be possible to extract the nitrate by mixing in large amount of potassium chloride and crystallizing KNO3 out, if just a mere nitrate is needed.