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Fantasma4500
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if you would want somehow to detonate the MnO7 you could try (obviously with great care) to pack it in a plastic bag, use a small detonator and blow
it into some aluminium, magnesium or magnalium powder soaked in xylene..
as youve heard before.. 50 mL
that could very easily get out of hand, very fast.. 
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Trotsky
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It seems that MnO7 breaks down very rapidly. After two days it's almost non-reactive. I imagine pure MnO7 is a different story, this was just
KMnO7+H2SO4 method stuff, so there were tons of impurities. It's easy enough to separate most of the crude out through a fine *metal* screen (some
plastics probably work fine, but I'm not gonna try it!)
It seems extremely temperature sensitive- when it's down below -3C, it loses all of it's magic. It's a cool demo for kids to drop stuff into it and
watch it go poof (keeping the kids well back and upwind of course!), but when it's cooled below freezing it's almost boring- the pops are few and far
between and many of the things you can react with it to get good bangs and snaps just result in slow smoking.
It seems that it's shock-insensitive, at least at cold temps. I tried whacking a drop with a hammer and got no reaction, somewhat disappointing.
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AndersHoveland
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I really do not think wax would work too well. Much better to use a liquid fuel that can easily be vaporized by the shock wave, and intimately mix
with the oxidizer. If wax was used it would just fly out in pulverised clumps. The surface area would be much lower, and thus you would get a much
slower reaction rate - probably not even an explosion at all.
It is true that somewhere else I stated that wax will work just as well as flammable liquid fuel in detonatable mixtures with chlorate. But this is
only because the detonation is happening within the wax, which is also already well pre-mixed with the oxidizer, it can be added. In the case
of an explosive blast suddenly shattering tubes and mixing pyrophoric fuel with oxidizer, the initial force of the blast is only enough to mix the
reactants, not to vaporize them. Because the reactants being mixed are not actually part of the first explosion itself.
I'm not saying let's go kill all the stupid people...I'm just saying lets remove all the warning labels and let the problem sort itself out.
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madscientist
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Quote: Originally posted by AndersHoveland  | One idea would be to place a tube of Mn2O7 at the center of a liquid fuel. The detonation of the Mn2O7 would suddenly cause mixture of the resulting
oxygen by-product with the fuel. My guess is that there would be a slight delay before the oxygen-fuel mixture spontaneously ignited. The initial
force of the explosion would blow out any flame, quickly thereafter the remnants of the Mn2O7 would spontaneously ignite. Placing the whole thing a
thick walled container to help contain the initial small detonation and fuel-oxygen mixture would likely also help.
A similar concept has been demonstrated with pyrophoric rocket fuels. A combination a pyrophoric fuel and oxidizer are placed in numerous tubes. A
small explosive at the center suddenly mixes them, and the rocket fuel combustion becomes part of the explosion. |
This idea is fantastically stupid and a fine way to end up in the ICU. 
I weep at the sight of flaming acetic anhydride.
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woelen
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| Quote: Originally posted by AndersHoveland |
I really do not think wax would work too well. Much better to use a liquid fuel that can easily be vaporized by the shock wave, and intimately mix
with the oxidizer. If wax was used it would just fly out in pulverised clumps. The surface area would be much lower, and thus you would get a much
slower reaction rate - probably not even an explosion at all.
It is true that somewhere else I stated that wax will work just as well as flammable liquid fuel in detonatable mixtures with chlorate. But this is
only because the detonation is happening within the wax, which is also already well pre-mixed with the oxidizer, it can be added. In the case
of an explosive blast suddenly shattering tubes and mixing pyrophoric fuel with oxidizer, the initial force of the blast is only enough to mix the
reactants, not to vaporize them. Because the reactants being mixed are not actually part of the first explosion itself. |
Please do not continue along this path of possible (and likely) selfdestruction!! This thing missed my attention two weeks ago, but
now I read this thread while it is raked up again, I consider it extremely bad advice. What if people really start trying this and get blown up or
maim themselves? It is easy enough to obtain the chemicals needed for this amazingly dangerous action. You probably never tried working with Mn2O7
yourself. I have done experiments with this (never more than single drops) and I can tell you it is already stupid to make test tubes full of this
liquid, let alone mixing it with fuels.
You have a responsibility, keep that in mind!
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Fantasma4500
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i partially agree, because... well if people dont know what manganese heptoxide is capable of doing before you can react, then they could accidentally
cut their own hand off aswell!
its very dangerous to handle manganese heptoxide, but you could see it as something to tame aswell, its interesting to take such reactive fluids and
''react'' with fuels, again very dangerous, things could go wrong in very little time.
quanities of manganese heptoxide above few drops amounts shouldnt be handled by a person who doesnt even know what it is (:
i wouldnt handle much more than a few drops of this stuff, but again this is because i live in a place thats not really suitable for handling stuff
that could go bang by small mistakes, tho i would probably if i had a better place to do it experiment with it and test equipment before handling it..
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Trotsky
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I have handled as much as 100ml of MnO7 now. It is incredibly reactive.
It is also very predictable, however. It carries none of the dangers of TATP. So long as you do not accidentally add large quantities of fuel, it
doesn't pose much danger.
Now, would I keep a tube sitting around filled with it? Nope. It must be kept highly secure to prevent any accidental and disastrous addition of
fuel.
The danger of MnO7 doesn't exactly increase as it's volume does- it scales with the increase in fuel. If you permit only the addition of small
quantities of organic compounds, you're alright. Serious precautions need to be taken before the addition of larger quantities of fuel (such as using
some sort of remote-addition mechanism).
The danger is really in the speed which it reacts. It's not like you can mix up some MnO7 and Toluene for later use. You can't even mix it up and
run away quick.
Where TATP may go off at any moment for no apparent reason. Carelessness may add to the danger, but the compound is inherently dangerous regardless
of whatever treatment it receives. MnO7, if treated with due caution, won't harm anyone.
Making a bomb with MnO7 requires some inventiveness and caution. It's potential as a weapon is fortunately extremely limited. It's a novel explosive
(it's such an odd explosive I'm not even sure that's the word), that's all. It might be neat to see how 100ml added rapidly, remotely, added to an
appropriate amount of toluene would react, to see the explosion. As far as I know, no explosive device has ever been made using MnO7. I hope that
anyone who might attempt such a thing would make themselves aware of all the dangers and take all possible precautions. I would never suggest that
anyone try such a thing. I wouldn't call it foolish, but anyone who approaches the task without great care and knowledge, and who doesn't place
safety as the absolute top priority should not even consider this.
However, I have been exposed to far too much manganese for a lifetime already (not from MnO7, however! If you are exposed to enough MnO7 to cause
manganism, I think you'll have died from it's other properties first ) and fear I may already have a mild case of manganism and wish to avoid further
contact with it.
[Edited on 31-3-2013 by Trotsky]
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AndersHoveland
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It is actually Mn2O7 and KMnO4.
Most chemists never bother to say "di-manganese heptoxide". There are other examples also, nitrogen tetroxide (N2O4),
phosphorous pentoxide (which confusingly can either be an amorphous substance with the ratio P2O5, or another solid compound with the definite
molecular formula P4O10 )
We simply know that "MnO7" does not exist, so do not bother using the prefix "di-". This can sometimes be a little confusing to those learning about
chemistry.
I'm not saying let's go kill all the stupid people...I'm just saying lets remove all the warning labels and let the problem sort itself out.
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woelen
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| Quote: | | It is also very predictable, however. It carries none of the dangers of TATP. So long as you do not accidentally add large quantities of fuel, it
doesn't pose much danger. |
This is not true. It is not predicatable and it can explode without apparent
reason. I have had such an explosion myself! Fortunately it was just a big drop of fairly pure Mn2O7, sitting on a watch glass. But the explosion was
really striking and my face was covered with many little brown spots (a few tenths of mm diameter) and the wall behind my desk also had many of these
little brown spots. This happened while I was watching a very peculiar phenomenon. The room in which I did the experiment was quite dusty and only
dimly lit. Every few seconds I saw a nice speck of light appearing on the drop of Mn2O7. This must have been due to a dust-particle landing on the
Mn2O7. Suddenly, however, the entire drop did BANG!
Mn2O7 can explode even without fuel, a dust particle landing on it can trigger the reaction! It then at once decomposes to MnO2 and O2.
Can you imagine what happens if this occurs with a test tube full of Mn2O7?
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SM2
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Yeah, best to treat this as if it were NCL3. BTW, is MN207 fairly stable when dissolved in an appropriate solvent? Like 50% Mn207 in isopropanol (am
I pushing it?). Perhaps lower concentrations in a different solvent. Brown bottle it for sure, and avoid contamination at all costs.
"Old men who speak of victory
shed light upon their stolen life
they - drive by night- and act as if they're
moved by unheard music." B. Currie
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Trotsky
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Maybe I underestimate the ability of people to experiment with it... Isopropanol is fuel. It will detonate if you were to try that.
That's the thing SM2- it's hard to have any organic contamination- as soon as any is present, it goes boom. It doesn't linger for a week to surprise
you. It happens more or less instantaneously.
| Quote: | This is not true. It is not predicatable and it can explode without apparent reason. I have had such an explosion myself! Fortunately it was just a
big drop of fairly pure Mn2O7, sitting on a watch glass. But the explosion was really striking and my face was covered with many little brown spots (a
few tenths of mm diameter) and the wall behind my desk also had many of these little brown spots. This happened while I was watching a very peculiar
phenomenon. The room in which I did the experiment was quite dusty and only dimly lit. Every few seconds I saw a nice speck of light appearing on the
drop of Mn2O7. This must have been due to a dust-particle landing on the Mn2O7. Suddenly, however, the entire drop did BANG!
Mn2O7 can explode even without fuel, a dust particle landing on it can trigger the reaction! It then at once decomposes to MnO2 and O2.
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You said without apparent reason! That's about as obvious as you can get. You were experimenting (playing) with it under dangerous circumstances and
experienced a predictable result. I'm glad it wasn't worse, but you can hardly call the compound unpredictable in this situation.
If you would have had a full test tube the result would have been more or less the same. I haven't known it to ever react past what it has available
for fuel, nor have I ever seen an indication that it happens. You likely had enough dust land on your drop that what wasn't used in reaction with the
fuel caused the rest of the drop to be splattered everywhere. Given the set up you describe, you're lucky you didn't have a fire from one of the tiny
droplets landing.
It will explode if rapidly heated and, I'm told (I haven't managed to replicate it) if it's struck hard.
I've also been told that it'll slowly oxidize a scratched poly watch glass. haven't seen it, I've only experimented with it on aluminum- I know that
plastics are mostly too difficult for it to react with, but I've not wanted to take the risk.
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DraconicAcid
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| Quote: Originally posted by SM2 | | Yeah, best to treat this as if it were NCL3. BTW, is MN207 fairly stable when dissolved in an appropriate solvent? Like 50% Mn207 in isopropanol (am
I pushing it?). Perhaps lower concentrations in a different solvent. Brown bottle it for sure, and avoid contamination at all costs.
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Dimanganese heptoxide will ignite non-flammable solvents such as dichloromethane (from personal experience). Do not even think of letting it get
anywhere near a flammable solvent such as isopropanol.
Please remember: "Filtrate" is not a verb.
Write up your lab reports the way your instructor wants them, not the way your ex-instructor wants them.
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Trotsky
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Don't worry about storing it- make up as much as you need for any given experiment and no more. It's so easy to make there there's no reason to
bother making enough that you'd need to worry about storing it.
Aside from water, which will ruin it, I don't know of a solvent that it won't destroy.
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DraconicAcid
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Cotton and Wilkinson (Advanced Inorganic Chemistry, p. 748, 4th Ed.) say that it can be extracted into carbon tetrachloride or chlorofluorocarbons.
(I misremembered this as being "carbon tetrachloride or chloroform", which is why I was dumb enough to try dichloromethane.)
Please remember: "Filtrate" is not a verb.
Write up your lab reports the way your instructor wants them, not the way your ex-instructor wants them.
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Trotsky
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That makes sense, that's not exactly oxidizable.
Still, I don't know that decreasing it's concentration would offer that much in terms of stability. But I haven't done it, so i can't say for
certain. It breaks down with time, even at low temps, so any sort of long term storage is probably inadvisable.
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DerAlte
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Like many experimenters, I have in the past played around producing minute quantities of Mn2O7 and NCl3. I must admit that anything that is dark and
oily and obviously covalent always has me cautious!
I have always assumed that Mn2O7 is, in fact, an endothermic compound like NCl3 (ΔHF298 +295kJ/mol). A web search for the value for manganese
heptoxide yielded no result, so I attempted to calculate it from the reactions
2KMnO4(s) + H2SO4(l) --> Mn2O7(l) + H2O(l) + K2SO4(s)
Or 2MnO4 - (aq) + 2H+ --> Mn2O7(l) + H2O(l)
And the assumed decomposition Mn2O7(l) --> 2MnO2(s) + 3O --> 2MnO2(s) + (3/2)O2(g)
I obiously made incorrect assumptions because each way gave a different answer. Also, all the thermodynamic quantities are not available (eg,
entropies). I also tried using bond energies but again data is too sparse and guessing isn’t good enough. Plus Pauling’s electronegativity method,
but again resuts are all over the place. I’m probably doing the calulations wrong but they always show a moderately negative ΔHF value (i.e.
stable or just stable at RT).
Does anyone here have the knowledge to work out the value definitively?
No one doubts that Mn2O7 is a damned dangerous oxidiser, but if it is endothermic to boot, greater caution should be observed than some of the above
comments suggest. Since it is reputed to explode if heated to 55C, it must be on the edge of endothermic, one assumes.
Der Alte
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Trotsky
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I can make some up and see if it really does explode at 55. I kind of think it won't, but we'll see!
How much do you think they were using when they tested that? I don't want to use much more than a mL but I suppose I could do three or four mL.
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woelen
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Even 1 ml can be quite dangerous if it explodes at once. Be careful. Use a blast shield and keep a distance from the stuff when doing the heating
experiment! If you do this experiment please report back on the result and on the loudness of the explosion.
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DerAlte
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Found a value for heat of formation: see Brauer, or a post on the 1st page of this thread by Davster where it is reproduced:
heat of formation: —177.4 kcal (20°C) dissociation at approx. 55°C, detonation at 95°C. In vacuum, rapid and explosive dissociation above
10°C.
From the same source:
Stable under refrigeration (—10 °C)provided anhydrous conditions are maintained. Reacts explosively with most organic compounds; attacks acetic
acid, acetic anhydride
and CCI4 even below room temperature. Dangerous compound!
The impact sensitivity of Mn2O7 is equal to that of mercuric
fulminate.
Der Alte
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