beeman - 18-11-2016 at 23:24
Hi,
I am doing a project on the formation of crystals and need ammonium nitrate.
There's ice packs that says there's Ingredients: Mixture of Nitrogenous Salts and Water.
Theres a red message saying it contains ammonium nitrate.
j_sum1 - 18-11-2016 at 23:31
Ok. So what is your question?
Posts with no citations belong in beginnings.
I am sure that a careful google search or even looking up the MSDS will give you information on your cold packs. And if you ever have a question then
someone will be glad to help.
aga - 18-11-2016 at 23:44
Hi and welcome to ScienceMadness !
To get your crystals, and hopefully purify the ammonium nitrate in the cold-pack, dissolve the contents in the minimum amount of boiling distilled
water, then filter into a fresh container.
Leave it to cool and some crystals of ammonium nitrate should start to form.
(optionally, stick it in the fridge once it's cooled and you'll get a few more crystals)
At this point, decant off the remaining water and you'll have more-or-less what you wanted.
Calculate the amount of water using a solubility table, e.g. https://en.wikipedia.org/wiki/Solubility_table
It says that 871g of ammonium nitrate will dissolve in 100ml of water @ 100 C, and only 192g will dissolve in 100ml @ 20 C (118g @ 0 C).
This means that the 'extra' ammonium nitrate has nowhere to go when the liquid cools, so it drops out as crystals.
If you have 1kg of pure powder, it should fully dissolve in about 115ml of boiling water.
Anything that does not dissolve is junk, and gets removed at the filtering step.
Edit:
Yes, SM etiquette says that if you are not following any published method then you should only post in Beginnings.
[Edited on 19-11-2016 by aga]
Metacelsus - 19-11-2016 at 06:33
You won't be able to decant off the water if you take a saturated solution of ammonium nitrate at 100 °C and cool it to room temperature. It will
just form a slush, and the only good way to remove the water is by vacuum filtration (gravity filtration doesn't really work well).