MeshPL
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Rather stupid smokebomb composition.
Old, not dry, ammonium thiocyanate and potassium permanganate crystals were separately powdered. Approximately 3:2 (based on volume, this was a guess,
not anything calculated) mixture of them was prepared, a spoon full in total. It was placed in a porcelain evaporating dish and ignited with a
magnesium strip (match may also work). It burned for a few seconds, but soon the flames died out and a moderate amount of acrid smoke was being
evolved for rougly ten seconds. When the fimehood was opened, it smelled like SO2 inside. The mixture melted as it smoked, and left a lot of black
residue.
This could be used as a rather toxic yet also exotic smokebomb.
This sums up my experiment with thiocyanate based "energetic" material. Next time I will use a more defined amount of NH4SCN and KMnO4. What
mass/molar ratio should I use?
[Edited on 30-5-2017 by MeshPL]
[Edited on 30-5-2017 by MeshPL]
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PHILOU Zrealone
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The black residue is probably some oxides of Mn (*)
You have two sets of equations...
1°) The decomposition of KMnO4 into stable molecules
2 KMnO4 --> K2O + 2 MnO2 + 3/2 O2
2°)The oxydation of ammonium thiocyanate...
but it is complex because you may have CO or CO2 and SO2 or SO3; the first one would be very toxic but if hot and exposed to air most of the CO will
burn further to CO2 by the external O2; the two last will probably not keep the SO3 as such...it will probably decompose to SO2 and 1/2 O2 due to the
heat of reaction
a) NH4SCN + 5/2 O2 --> N2 + 2 H2O + SO2 + CO
b) NH4SCN + 6/2 O2 --> N2 + 2 H2O + SO2 + CO2
c) NH4SCN + 6/2 O2 --> N2 + 2 H2O + SO3 + CO
d) NH4SCN + 7/2 O2 --> N2 + 2 H2O + SO3 + CO2
So by combining equation 1 with the different 2...you get:
2a) 3 NH4SCN + 10 KMnO4 --> 3 N2 + 6 H2O + 3 SO2 + 3 CO + 5 K2O + 10 MnO2
2b) NH4SCN + 4 KMnO4 --> N2 + 2 H2O + SO2 + CO2 + 2 K2O + 4 MnO2
2c) NH4SCN + 4 KMnO4 --> N2 + 2 H2O + SO3 + CO + 2 K2O + 4 MnO2
2d) 3 NH4SCN + 14 KMnO4 --> 3 N2 + 6 H2O + 3 SO3 + 3 CO2 + 7 K2O + 14 MnO2
So you have now the molar ratios. I recommand you to use the ratio 2b or 2c to get the best energy output and gaseous products.
Beware that upon standing/storage the mix may suffer some ion exchange and become equivalent to a mix of NH4MnO4 and KSCN...and NH4MnO4 must be a
sensitive energetic compound.
About thiocyanate based energetic material you should try NH4ClO4 and NH4SCN...or KClO4/NH4SCN eventually with some fine aluminium dust.
(*) MnO2 is considered because the most usual but depending onto the reaction temperature, dispersion, size of the batch...you may have side
production of MnO, Mn2O3, Mn3O5
[Edited on 30-5-2017 by PHILOU Zrealone]
PH Z (PHILOU Zrealone)
"Physic is all what never works; Chemistry is all what stinks and explodes!"-"Life that deadly disease, sexually transmitted."(W.Allen)
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MeshPL
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I do not have KClO4, only KClO3. But the latter will form NH4ClO3, so it is a no no. I may try with KSCN, but I don't have it, I would have to make it
(KOH and NH4SCN should do it).
Thanks for your response! It is really helpful. I'm not an expert on pyrotechnics and stechiometry of such reactions, therefore I really want to thank
you.
[Edited on 31-5-2017 by MeshPL]
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MeshPL
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I made some NH4SCN and permanganate mix with more accurate stechiometry and tested it.
Ammonium thiocyanate, which was rather old and has absorbed some water, was powdered as well as was potassium permanganate. Permanganate could be
powdered a little better, but the mortar used was rather small and larger one was not used. About 1g (slightly more probably) of thiocyanate and 10g
of permanganate were mixed together in a beaker with a glass spatula and put on a porcelain dish. This gave a mix of roughly 1:4 molar ratio, as the
more accurate scale was not available, 1:10 mass ratio of reactants was accepted as a good approximation, which produces desired molar ratio in a
reasonable approximation seeing as inaccuracy of the scale would put it out of balance anyway.
The mix was ignited with magnesium strip and burned vigorously with a lilac flame, typical for potassium compounds. It was a considerable improvement
over last test, which mostly smoldered. The residue left was dark, with a blue-green tint, it was also frothy, with a lot of gases trapped. The amount
of smoke emmited was considerable, although it did not overwhelm the fumehood. Nevertheless, the outdoor gas outlet, which leads from the fumehood's
ventillator, emmited enough of that smoke to produce a considerable cloud outside the school. The heat emmited cracked the porcelain dish, although it
was not in the good state at the beginning in the first place. (Dish with slight cracks was chosen so as not to destroy a new, good one) Acrid smell
was not noticed this time, although had the fumehood been opened later, the smell would probably have been still present.
This was a clear improvement. Next time I will try a urea based smoke mix, which may probably also be used to produce some noxious smoke (think NH3).
This time calculations will be easier though...
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Elemental Phosphorus
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If you would like to make KClO4 from your chlorate, you could always disproportionate the chlorate to perchlorate by heating in a clay crucible at
about 400 degrees C for a while should decompose it to perchlorate. Remember that perchlorate is a much less vigorous oxidiser than either
permanganate or chlorate. I also think that equation 2a would provide the most power, and the toxicity shouldn't be much of an issue unless you use it
in a confined space and heavily breathe the fumes, since gases generated by oxgen poor explosives never seem to be a problem, and the CO should burn
to CO2 anyhow.
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PHILOU Zrealone
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Quote: Originally posted by MeshPL  | I made some NH4SCN and permanganate mix with more accurate stechiometry and tested it.
Ammonium thiocyanate, which was rather old and has absorbed some water, was powdered as well as was potassium permanganate. Permanganate could be
powdered a little better, but the mortar used was rather small and larger one was not used. About 1g (slightly more probably) of thiocyanate and 10g
of permanganate were mixed together in a beaker with a glass spatula and put on a porcelain dish. This gave a mix of roughly 1:4 molar ratio, as the
more accurate scale was not available, 1:10 mass ratio of reactants was accepted as a good approximation, which produces desired molar ratio in a
reasonable approximation seeing as inaccuracy of the scale would put it out of balance anyway.
The mix was ignited with magnesium strip and burned vigorously with a lilac flame, typical for potassium compounds. It was a considerable improvement
over last test, which mostly smoldered. The residue left was dark, with a blue-green tint, it was also frothy, with a lot of gases trapped. The amount
of smoke emmited was considerable, although it did not overwhelm the fumehood. Nevertheless, the outdoor gas outlet, which leads from the fumehood's
ventillator, emmited enough of that smoke to produce a considerable cloud outside the school. The heat emmited cracked the porcelain dish, although it
was not in the good state at the beginning in the first place. (Dish with slight cracks was chosen so as not to destroy a new, good one) Acrid smell
was not noticed this time, although had the fumehood been opened later, the smell would probably have been still present.
This was a clear improvement. Next time I will try a urea based smoke mix, which may probably also be used to produce some noxious smoke (think NH3).
This time calculations will be easier though... |
You see everything is better once you masterize the chemistry and aftermath behind ;-)
With urea beware that you will produce also if into reducing conditions (not enough oxidizer) some cyanhydric acid/cyanides...but since HCN is
endothermic and gaseous, in principle, it will burn/explode to H2O and CO/CO2
PH Z (PHILOU Zrealone)
"Physic is all what never works; Chemistry is all what stinks and explodes!"-"Life that deadly disease, sexually transmitted."(W.Allen)
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MeshPL
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Just tried stochiometric mixture of urea with KClO3 (I prefer it to permanganate as it is not coloured) but it did not work, even when placed on a
burner. Of course it dod combust somewhat, but with no flames, no gas, jeust melted and heated up slightly, enough to crack porcelain dish (that was a
good one, damn.) I may need to get some steel cans to do such reactions.
That's weird as a nonstochiometric mixture of urea and permanganate clearly did react and smoked.
If I get a working mix, I'll do a proper topic.
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PHILOU Zrealone
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| Quote: Originally posted by MeshPL | Just tried stochiometric mixture of urea with KClO3 (I prefer it to permanganate as it is not coloured) but it did not work, even when placed on a
burner. Of course it dod combust somewhat, but with no flames, no gas, jeust melted and heated up slightly, enough to crack porcelain dish (that was a
good one, damn.) I may need to get some steel cans to do such reactions.
That's weird as a nonstochiometric mixture of urea and permanganate clearly did react and smoked.
If I get a working mix, I'll do a proper topic. |
What are your equations, calculations and stoechiometric ratio...just to see if you masterize it wel now and that you did'nt do a mistake.   ...
Urea is not a very good fuel on its own...maybe add a little Al dust or C black of fume...
PH Z (PHILOU Zrealone)
"Physic is all what never works; Chemistry is all what stinks and explodes!"-"Life that deadly disease, sexually transmitted."(W.Allen)
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MeshPL
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CO(NH2)2 + KClO3 ---> CO2 + 2H2O + KCl + N2
Simple enough.
Molar mass of urea: 12+16+2×14+4=60
Molar mass of potassium chlorate: 39+35,5+3×16=122,5
A near 1:2 ratio.
I used 3g of urea and 6 grams of chlorate, well powdered and mixed.
At rt net enthalpy change permole of reactants is -638,45 kj/mole (based on my chemical tables handbook) I didn't bother calculating it at higher
temperature though, but the temperature usually doesn't matter. Unless calculating some equillibrium constants.
[Edited on 5-6-2017 by MeshPL]
[Edited on 5-6-2017 by MeshPL]
[Edited on 5-6-2017 by MeshPL]
[Edited on 5-6-2017 by MeshPL]
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PHILOU Zrealone
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| Quote: Originally posted by MeshPL |
CO(NH2)2 + KClO3 ---> CO2 + 2H2O + KCl + N2
Simple enough.
Molar mass of urea: 12+16+2×14+4=60
Molar mass of potassium chlorate: 39+35,5+3×16=122,5
A near 1:2 ratio.
I used 3g of urea and 6 grams of chlorate, well powdered and mixed.
At rt net enthalpy change permole of reactants is -638,45 kj/mole (based on my chemical tables handbook) I didn't bother calculating it at higher
temperature though, but the temperature usually doesn't matter. Unless calculating some equillibrium constants.
|
Perfect .
Then you face the same as KClO3/C mix or KClO3/SiC mix...hard to ignite and burning slowly except if in large quantity and very intimately mixed (very
fine mesh).
Conclusion:
--> Activation energy is too high for the energy produced.
--> Need for a catalyst...May I suggest CuO, MnO2 or KMnO4
--> Need for a better fuel ... Al or C or suggar aside from urea...
--> Or both
The catalyst is needed only in low %...MnO2 or KMnO4 are known to reduce the T° for O2 liberation out of the KClO3....
CuO will act by complexation with urea upon fusion generating Cu(NH3)4(2+) and Cu(2+) is reactive towards chlorate...
Sensitivity will be improved but storage may become problematic especially in moist environment/atmosphere...
Last idea change urea for melamine obtained by fusing urea...
3 H2N-CO-NH2 --> (-C(NH2)=N-)3 + 3 H2O
You will improve the fuel power.
[Edited on 5-6-2017 by PHILOU Zrealone]
PH Z (PHILOU Zrealone)
"Physic is all what never works; Chemistry is all what stinks and explodes!"-"Life that deadly disease, sexually transmitted."(W.Allen)
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MeshPL
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I tried adding a catalyst. It helped. A bit.
4g of potassium chlorate and 2g of urea were thoroughly powdered separately and than well mixed with a little of CuO and MnO2. The amount of either
oxide was approximately equal to 2 rice grains (I have no better way of comparing such small amounts...). The mixture was put on an aluminium foil and
ignited with magnesium ribbon. It did not burn but smoldered slowly and released quite a lot of smoke (yet it did it also slowly and fumehood was not
overwhelmed). No smell of ammonia was noticed in the fumehood after the experiment. The residue was black and looked "goopy" although it was solid.
I may need more catalyst next time.
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MeshPL
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Did another experiment. Fuel will not help mixtue burn unless in large quantities. However both CuO and MnO2 are suitable catalysts. With enough
catalyst to make mixture dark grey or brown, it smolders vigorously, smokes quite a bit and may even heat up to redness. It also leaves a noticable
smell of nitrogen oxides in the air.
I wonder if other metal oxides also work.
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PHILOU Zrealone
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| Quote: Originally posted by MeshPL | I tried adding a catalyst. It helped. A bit.
4g of potassium chlorate and 2g of urea were thoroughly powdered separately and than well mixed with a little of CuO and MnO2. The amount of either
oxide was approximately equal to 2 rice grains (I have no better way of comparing such small amounts...). The mixture was put on an aluminium foil and
ignited with magnesium ribbon. It did not burn but smoldered slowly and released quite a lot of smoke (yet it did it also slowly and fumehood was not
overwhelmed). No smell of ammonia was noticed in the fumehood after the experiment. The residue was black and looked "goopy" although it was solid.
I may need more catalyst next time. |
Yes the optimum quantity of catalyst is a trial-error experimentation.
| Quote: Originally posted by MeshPL | Did another experiment. Fuel will not help mixtue burn unless in large quantities. However both CuO and MnO2 are suitable catalysts. With enough
catalyst to make mixture dark grey or brown, it smolders vigorously, smokes quite a bit and may even heat up to redness. It also leaves a noticable
smell of nitrogen oxides in the air.
I wonder if other metal oxides also work. |
If the mix is not very energetic, then indeed the need for larger amount is logical to get the reaction to proceed at a noticeable speed (the heat of
reaction is better used by the self-confinement...which otherwise is in great portion lost into the surrounding media (suppport, side walls and
air)...
Scaling down is a way to keep/take the control over very reactive/exothermic reaction...and reversely scaling up is a way to activate poorly
reactive/exothermic reactions.
The provided oxydes are the more usual known candidates (cheap, OTC available)...other oxides may work but it is also a trial and error process since
some oxides are combustion modifiers to increase burning rate (catalyst) and other will reduce it (poisoning of reaction/ inhibitors (negative
catalyst)).
Maybe PbO2 will prove to be valuable catalyst just like some peroxides CuO2, ZnO2...or perferates like K2FeO4 (iron based (per)manganate brother)
Iron oxides are OTC but effect might be + or -...to be tested (FeO, Fe2O3)...
PH Z (PHILOU Zrealone)
"Physic is all what never works; Chemistry is all what stinks and explodes!"-"Life that deadly disease, sexually transmitted."(W.Allen)
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