Sciencemadness Discussion Board

What is it and what are it's properties?

Emmasis - 11-11-2012 at 19:10

I just concentrated KNO3 with 50% (Volume) NH4NO3 in warm water and allowed it to crystallize.
What is the solution that is left over?
Is there anything I can do with it?
Thanks for the help all!

[Edited on 12-11-2012 by Emmasis]

12AX7 - 11-11-2012 at 20:32

NH4NO3???

KNO3, probably of low purity, is the only thing that's going to crystallize at STP. NH4NO3 absorbs water and remains in solution strongly, in fact if left out in air it will absorb moisture to make its own solution.

Suggest moving to Beginnings.

Tim

Emmasis - 11-11-2012 at 20:57

So let me get this straight, if I were to take AN straight out of an ice pack, dissolve it in warm water and let it cool overnight, I would only have aqueous AN no crystals.
RIGHT?
Quote: Originally posted by 12AX7  
NH4NO3???

KNO3, probably of low purity, is the only thing that's going to crystallize at STP. NH4NO3 absorbs water and remains in solution strongly, in fact if left out in air it will absorb moisture to make its own solution.

Suggest moving to Beginnings.

Tim

12AX7 - 11-11-2012 at 21:43

If you dissolved it in a minimal quantity of very hot water, it may crystallize on cooling.

Those crystals would tend to absorb moisture over time, though a mass amount at the bottom of a saturated solution will take more than overnight to absorb enough moisture.

If the water wasn't very warm, or the concentration not quite saturated, it might not crystallize.

If you have no other identification, it's quite possible you have something else, for example urea, which absorbs heat when dissolved in water, but is stable in air and crystallizes with a needle-like form.

Tim

tetrahedron - 12-11-2012 at 02:22

long needles formed overnight from the recrystallization of NH4NO3 fertilizer:
nh4no3.jpg - 447kB

note that some are seriously bent, which is unheard of for ionic compounds..might this be due to organic fillers? how can i tell NH4NO3 and urea apart? the crude product smells very slightly sweet, but not urea like.

weiming1998 - 12-11-2012 at 03:26

Quote: Originally posted by tetrahedron  
long needles formed overnight from the recrystallization of NH4NO3 fertilizer:


note that some are seriously bent, which is unheard of for ionic compounds..might this be due to organic fillers? how can i tell NH4NO3 and urea apart? the crude product smells very slightly sweet, but not urea like.


It's very easy to tell urea apart from ammonium nitrate.

1, Combine unknown crystals with NaOH. Ammonia, in large quantities, will form quickly if the crystals are NH4NO3. Otherwise it is urea.

2, Add H2SO4/HCl to the crystals, then add copper. The acidified NO3- will attack copper, while urea added to H2SO4 or HCl does not attack copper.

3, Grind crystals, combine with some charcoal, then ignite the mix. Again, urea won't do anything, while ammonium nitrate will oxidize the charcoal, burning rapidly.


Emmasis - 12-11-2012 at 08:14

So let me get this straight, if I were to take AN straight out of an ice pack, dissolve it in warm water and let it cool overnight, I would only have aqueous AN no crystals.
RIGHT?
Quote: Originally posted by 12AX7  
NH4NO3???

KNO3, probably of low purity, is the only thing that's going to crystallize at STP. NH4NO3 absorbs water and remains in solution strongly, in fact if left out in air it will absorb moisture to make its own solution.

Suggest moving to Beginnings.

Tim

tetrahedron - 12-11-2012 at 09:03

Quote: Originally posted by Emmasis  
So let me get this straight, if I were to take AN straight out of an ice pack, dissolve it in warm water and let it cool overnight, I would only have aqueous AN no crystals.
RIGHT?

wrong, you can definitely get some crystals. i think what 12AX7 meant is that the KNO3 being less soluble would crystallize out first.
Quote: Originally posted by Emmasis  
I just concentrated KNO3 with 50% (Volume) NH4NO3 in warm water and allowed it to crystallize.
What is the solution that is left over?
Is there anything I can do with it?

the left-over solution will be mostly NH4NO3. you can boil it down, let it cool slowly and recover some NH4NO3. or you can sprinkle it in your garden =)

out of curiosity how did you end up with such a mixture? and what's with the repost?
Quote: Originally posted by tetrahedron  
long needles formed overnight from the recrystallization of NH4NO3 fertilizer:
[img]
note that some are seriously bent

turns out bent ammonium nitrate needles do exist:

http://www.tandfonline.com/doi/abs/10.1080/14786442108636195
Quote:

Emmasis - 12-11-2012 at 10:58

I didn't mean to get so off topic, I am positive it is AN.
I am wondering about the leftover solution that I have from the KNO3 & NH4NO3, after crystallization.
thank you

Emmasis - 12-11-2012 at 11:00

I don't know how the re-post happened,
Sorry all
Quote: Originally posted by tetrahedron  
Quote: Originally posted by Emmasis  
So let me get this straight, if I were to take AN straight out of an ice pack, dissolve it in warm water and let it cool overnight, I would only have aqueous AN no crystals.
RIGHT?

wrong, you can definitely get some crystals. i think what 12AX7 meant is that the KNO3 being less soluble would crystallize out first.
Quote: Originally posted by Emmasis  
I just concentrated KNO3 with 50% (Volume) NH4NO3 in warm water and allowed it to crystallize.
What is the solution that is left over?
Is there anything I can do with it?

the left-over solution will be mostly NH4NO3. you can boil it down, let it cool slowly and recover some NH4NO3. or you can sprinkle it in your garden =)

out of curiosity how did you end up with such a mixture? and what's with the repost?
Quote: Originally posted by tetrahedron  
long needles formed overnight from the recrystallization of NH4NO3 fertilizer:
[img]
note that some are seriously bent

turns out bent ammonium nitrate needles do exist:

http://www.tandfonline.com/doi/abs/10.1080/14786442108636195
Quote:

Emmasis - 12-11-2012 at 11:05

So, what % the of original volume should I boil it down to?
I do not want it to decompose.
Thank you

tetrahedron - 12-11-2012 at 11:31

first boil off only a little water, cool down to room temperature and remove the first crop of crystals. now you have a saturated solution (about 200g/100mL). the solubility at 0°C is about half this value. reduce to at most 50% the volume and repeat. this is how i got the crystals above. decomposition (with very noticeable evolution of gas) doesn't set in until dryness.

Emmasis - 12-11-2012 at 11:36

But, you still believe my crystals to be weak KNO3?
I got the long needle crystals out of it.
Thank you for all your help understanding the process!!!
Quote: Originally posted by tetrahedron  
first boil off only a little water, cool down to room temperature and remove the first crop of crystals. now you have a saturated solution (about 200g/100mL). the solubility at 0°C is about half this value. reduce to at most 50% the volume and repeat. this is how i got the crystals above. decomposition (with very noticeable evolution of gas) doesn't set in until dryness.


[Edited on 12-11-2012 by Emmasis]

tetrahedron - 12-11-2012 at 13:58

no idea, try and report back ;p

in the meantime i heated some crystals in a spatula on a flame. first they melted, then the melt started bubbling vigorously with lots of smoke but no smell (thus i can rule out urea), but near the end it caught fire and left a patina of residue. unless anyone has ever seen ammonium nitrate burn this means there were still organic fillers present :(