Ammonium Nitrate and Copper reaction?

[YT2095]

can anyone help me out a little, I was breaking up some Ammonium nitrate with a cheap fork as it was starting to go solid, some of it stuck to the fork and after a while the crystals on it turned deep blue (proving copper).

I`ve mixed in a test tube a strong soln of the AN and put in some copper wire, there was a slight smell of ammonia at 1`st until the soln started to turn blue, now it looks like ink and the copper metal is evolving gas, slightly reminiscent of Nitric acid in smell.

can someone explain to me what the reaction is?

 

some places say it will make copper nitrate if heated and the ammonia is allowed to evaporate (there`s no ammonia smell though?)

 

other sources say it will make a very powerfull impact sensitive explosive? (I`f that`s the case then I`m pouring it away and keeping copper well away from AN in future!

Tatramine Copper (II) Nitrate is suposed to be the name.

 

any ideas?

[YT2095]

Oooops! nevermind, I`ve solved it, and it IS dangerous

 

it forms Cu(NH3)4(NO3)2

 

it IS the tetramine I mentioned above.

 

right, now to flush it down the toilet (Carefully!)

[JMAPScience]

sounds like a interesting experiment

[Enthalpy]

Ammonium nitrate IS dangerous stuff alone. Even without a fuel, it's a strong explosive, though not very sensitive.

A little bit of fuel making it sensitive to heat locally can make the reste detonate.

Many metals, even not efficiently reducing ones, act as catalysts to start its decomposition.

And just heat can make pure ammonium nitrate sensitive.

[ajkoer]

The starting materials are a copper alloy, air, moisture and NH4NO3.

 

An electrochemical reaction proceeds with the reduction of the NH4NO3 to NH4NO2 (which is very poisonous and unstable usually forming N2, but the dry salt can explode, especially in the presence of impurities) and then further reduce to NH3. Interestingly, you did actually detect the smell of ammonia.

 

Copper is a known sensitizer for ammonium nitrate (that is, NH4NO3 is now transformed into a sensitive explosive, probably due to the creation of NH4NO2 and at higher temperatures, other unstable intermediaries, so be very very wary). I would suspect a copper alloy is even more problematic due to the possible mixed metal electrochemical based REDOX reaction alluded to above.

 

I have actually experience with the REDOX reaction of aqueous KNO3 with Aluminum foil, where a similar electrochemical reaction ensues. I avoided using an excess of the Al as I wanted just KNO2, but I removed some of the nitrite solution for testing. As a consequence of the now relative increase in Al, the next day I was surprised when greeted by a rush of escaping NH3 gas upon opening the vessel with the remainder of the once aqueous KNO3.

 

[Edit] If a mixed salt is formed with ammonia, it could be, indeed, Cu(NH3)4(NO3)2, the later having been actually reported as forming in nitrate ammunitions upon warming in contact with corroding Copper (this could be galvanic corrosion from the action of NH3, H2O and O2 on Cu producing cupric ammonium hydroxide). The cupric ammonium nitrate could then be formed via the dissociation of NH4NO3 into NH3 and HNO3 upon mild heating (similar to what happens on heating NH4Cl) acting on the Cu(NH3)4(OH)2.

Edited September 29, 2014 by ajkoer