The title sums it up, I am getting small amounts of ammonia evolved from a pyrotechnic comp and I don't think it's normal. In fact, it's rather weird
as there should be no ammonium salt anywhere in the compound (nor nitrate or amine for that matter).
It's a blue fountain comp containing, in various proportions:
KCl04, CuO, Red Gum, Parlon, Dextrin, Magnalium
(actually, I think it's the 'Veline' blue comp)
I wanted to try it as the base for a blue sparkler so I mixed a little water and CMC into the comp and stirred to the right consistency. While
stirring, I was struck by the smell of ammonia. Not huge amounts, I mean the mix wasn't bubbling away and was not getting noticeable warmer, but
ammonia has an unmistakeable aroma.
My question is where might this be coming from and should I be worried?
My KClO4 was prepared by precipitation from NH4CLO4 and KNO3. It was well washed but is it possible some NH4NO3 remained on the KClO4 crystals and
that this is where the NH3 is coming from, probably catalysed by the CuO?
Cheers
Angel
[Edited on 3-9-2019 by AngelEyes]hissingnoise - 3-9-2019 at 03:25
Quote:
Is it possible some NH4NO3 remained on the KClO4 crystals and that this is where the NH3 is coming from, probably catalysed by the CuO?
Yes, it is ─ and no catalysis required.
The only way to obtain guaranteed pure KClO4 is to distill with dilute H2SO4 a solution of HClO4
from your starting salt and neutralise with K-carbonate, chloride, nitrate or hydroxide...
KClO4 is almost water-insoluble @0°C
[Edited on 3-9-2019 by hissingnoise]woelen - 3-9-2019 at 04:15
You also can make KClO4 from NH4ClO4 by adding a little excess amount of KOH to NH4ClO4. Assure that you have excess KOH, it is better to have a
little bit too much KOH, than having an excess of ammonium ions. You should heat the mix until it boils and add so much water that all solid material
dissolves in the boiling hot water. A good starting point is 50 grams of NH4ClO4 with 100 ml of water and then adding a little more than a
stoichiometric amount of KOH to this. Add little amounts of water until all solid dissolves at boiling temperature. The clear solution must be boiled
for a while until no more smell of ammonia is present above the hot liquid (careful! do not stick your nose in the beaker with hot liquid, but waft
air from above the beaker to your nose). Next, allow the liquid to cool down. This will give a lot of crystals of KClO4. Once cooled down, put in a
fridge to further cool down. Put the crystal mass on a coffee filter and soak up as much of the water with tissue under the coffee filter. Put the
just moist crystal mass in distilled water and boil again and add so much water that all of the solid just dissolves. Then allow to cool down again,
put in the fridge and collect your crop of crystals again. Spread on a clean glass surface and allow to dry in a warm place, free of dust. In this way
you get very pure KClO4, with no left over alkalinity and no ammonia in it.
I have done this myself a few times. It works quite well. The first step of mixing NH4ClO4 with water and KOH is unpleasant, it evolves a lot of
ammonia and must be done outside, but once most ammonia is driven off, the process is easy, provided you have some basic glassware and a decent
heater.
[Edited on 3-9-19 by woelen]AngelEyes - 3-9-2019 at 09:13
Thanks for the swift replies. I'll see if I can acquire some KOH and try Woelen's method.
Cheers
Angel.hodges - 3-9-2019 at 16:31
You don't even need an ammonium salt. If there is any nitrate remaining in the mix (including the original KNO3), it can be reduced to ammonia by
active metals such as the aluminum and magnesium you have in the mix.
At one time, a popular brand of drain cleaner contained sodium hydroxide, potassium nitrate, and aluminum slivers. The smell of ammonia was
unmistakable when using it to unclog drains. I guess they added the nitrate so that ammonia would be evolved instead of hydrogen - perhaps for safety
reasons, or maybe psychological reasons so the user would smell something strong and assume it was working well.
You don't even need an ammonium salt. If there is any nitrate remaining in the mix (including the original KNO3), it can be reduced to ammonia by
active metals such as the aluminum and magnesium you have in the mix.
.....
I know that Al will reduce NO3- to NH3 in basic conditions (pH around 9).
The mechanic of the reaction is claimed to involve the presence of electrons and aluminum alloy composition with a role for ' intermetallic species'.
I suspect that the hydrogen atom radical (sometimes referenced as nascent hydrogen, see this albeit dated source at http://www.jbc.org/content/48/2/489.full.pdf ) plays a role.
"Aluminum, the most abundant metal element in the earth's crust, is able to reduce nitrate, but the passivation of aluminum limits its application.
Here we report Al alloys (85% Al) with Fe, Cu or Si for aqueous nitrate reduction. The Al alloys particles of 0.85-0.08 mm were inactivate under
ambient conditions and a simple treatment with warm water (45 °C) quickly activated the alloy particles for rapid reduction of nitrate. The Al-Fe
alloy particles at a dosage of 5 g/L rapidly reduced 50 mg-N/L nitrate at a reaction rate constant (k) of 3.2 ± 0.1 (mg-N/L)1.5/min between pH 5-6
and at 4.0 ± 0.1 (mg-N/L)1.5/min between pH 9-11. Dopping Cu in the Al-Fe alloy enhanced the rates of reduction whereas dopping Si reduced the
reactivity of the Al-Fe alloy. The Al alloys converted nitrate to 20% nitrogen and 80% ammonium. Al in the alloy particles provided electrons for the
reduction and the intermetallic compounds in the alloys were likely to catalyze nitrate reduction to nitrogen."
