Sciencemadness Discussion Board

ammonium nitrate test...

Chemist514 - 24-6-2006 at 23:55

whats a simple way to test if a "cold pack" has ammonium nitrate or urea in it?
I am just wondering what to label the bottle for the collection...
thanks if you can help.

enhzflep - 25-6-2006 at 01:41

Urea melting point 135-137 deg c
Ammonium Nitrate melting point 170 deg c

Urea 10% solution pH = 7.2
Ammonium Nitrate ??% solution pH = 5.4

So, urea's basic and melts fairly low
ammonium nitrate's acidic and melts some 25% higher

Check msds for anything further. Both of these are from jtbaker

[edit: try mixing with strong solution of strong akali e.g NaOH. If you smell ammonia then it's amonium nitrate]

[Edited on 25-6-2006 by enhzflep]

Chemist514 - 25-6-2006 at 07:29

Thanks so much!

Well it is slightly acidic.. blue litmus paper... pink.
I added a few "bits" of sodium hydroxide... ammonia.
It seemed to have ALOT of impurities, I filtered alot of it out and recrystalized it from solution, hard to dry.. wow!
(about 3 hours in the oven on LOW!) nice white crystals!
Off to clean up my mercury now... thanks again.

all this.. and all i wanted was a chemistry set for the kids!

12AX7 - 25-6-2006 at 10:11

What shape are the crystals, or is it more like an undefined mush?

Tim

ammonium nitrate crystals

Chemist514 - 25-6-2006 at 11:46

Hi.

They are now very tightly packed tiny needles? (very short though) pure white but certainly very small crystals, i almost stopped at mush but decided to go a bit longer.
It had brown bits that didnt dissolve in water in it and a couple of grey flakes where in the filter paper, also it wasnt white crystals i started with, slight amber spheres,i had to filter it near boiling or it would crystalize in the funnel...
but you are hinting at water still being in my sample? indeed... i suspect alot, but i hear it can detonate and i dont want to bring about those conditions... is calcium chloride of use here? (some dying chemical?)
maybe i should have used something other then water?

Perhaps this will make more sense when me and the kids get to "evaporation" in the chemistry set! lol
(its a Chem C3000, huge... bigger then the one my mom bought for me. haha)

12AX7 - 25-6-2006 at 12:45

I was just asking the shape.

I hate needles, don't you? :mad: Suppose it doesn't matter if you just want dried cake, but if you're trying to fractionally crystallize (by heating, evaporating, then cooling without evaporation to get a crop of crystals, then filtering the liquor from the crystals and repeating) a chemical that grows like that, it's often a crusty mat of fine, hard-to-filter crystals.

Don't worry too much about explosions, AN isn't very explosive (low velocity of detonation compared to other explosives, and it takes a big honking cap to light), though more sensitive at that temp I suppose. It's more prone to decomposition (to N2O and H2O IIRC?), so you don't want to go too high. I suppose you could dry it with a dessicant but you may go through a lot, and it would take longer than just warm/hot dry air.

Chemist514 - 25-6-2006 at 13:05

I just wanted it to look more like the chemicals ive bought A.C.S standard, and i figured i might as well start playing with some of the chems i picked up that are not in my "needed" list, it was the second most questionable after my Clear-Line drain opener, pink sulfuric acid anyone?
on with the show at hand...

Thanks for that info! very helpful, since my purpose is general chemistry experiments (textbook type stuff only..)
I think as long as i can come close to technical grade im prolly ok.

I was going to finish by grinding in a morter and pestle and baking on low one more time... i dont have a desicator but im prolly going to buy one as i see much fun in finding less then obvious sources for chemicals.

Thanks so much for you help!

p.s : can i do the same thing to my old jar of cobalt chloride i got as a donation? (im less then happy about doing that as its in its original fisher bottle but is a fused mass on the bottom of the jar...A.C.S too. sigh.)

Chris The Great - 25-6-2006 at 14:59

Urea also makes ammonia when mixed with sodium hydroxide, so keep that in mind (it is broken down into sodium cyanate and ammonia).

DeAdFX - 25-6-2006 at 16:09

Does sodium hydroxide decompose the urea in to cynate and ammonia catalytically or is the reaction based upon stoichiometry

12AX7 - 25-6-2006 at 17:24

Er, isn't that a hydrolysis process? H2N-CO-NH2 + 2H2O = (NH4)2CO3 (which sublimes easily). To make cyanate would have to break those hydrogens off one amine to form a C=N triple bond. I recall ammonium cyanate NH4OCN isomerizes to urea, but that doesn't mean the reverse is readily possible, in fact the isomerization is thermal so urea would be more stable anyway, correct?

At any rate, urea hydrolysis is probably slower, I don't know what attack rates are like on a carbonyl... but an ammonium salt has it available right there, the presence of ammonia will be immediate and unmistakable.

Tim

neutrino - 25-6-2006 at 18:04

I saw this test for cold pack prills at RS a while ago and thought it might be of interest.
Quote:
Posted by Darkbloodpriest at RS

I would simply do the old newspaper smoke bomb trick described in Lowry's makeshift arsenal.
[kewl recipe]Simply grind up your prills....pour them into a equal amount of water, and turn it into a slush.
Dip some newspaper into it, and let it soak for about 10 minutes. Hang to dry someplace, and light afterwards. If you get a fizz and pure white smoke, it's AN. If not.....[/kewl recipe]

DeAdFX - 25-6-2006 at 19:57

I found the newspaper thing to work unreliably... Magnesium works nicely but Urea does have oxygen in it.

Chris The Great - 26-6-2006 at 02:03

The reaction is stiochometric and proceeds easily, giving huge amounts of ammonia in my experience.

chromium - 26-6-2006 at 02:11

AN decomposes on heating without leaving any solid residue. All products are gaseous. Not so with urea.

[Edited on 26-6-2006 by chromium]