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woelen
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Peroxo chromate
Just accidently, I discovered a very energetic mix, which is easy to ignite and explodes violently, even when not confined, at quantities of less than
10 mg 
Some time ago, I made the brown salt K3CrO8, which has a very high oxygen content. This can be made from an ice-cold (-10 C or so) lemon yellow
concentrated solution of K2Cr2O7 and KOH. Take 1 mol of K2Cr2O7 for 3 mols of KOH and dissolve in as little as possible water.
Add SLOWLY, drop by drop, 30% H2O2 (also ice cold) to this yellow solution. If this is done slowly and temperature is not allowed to go over 0 C, then
brown crystals of K3CrO8 separate from the liquid. For each mol of K2Cr2O7 take appr. 6 mols of H2O2.
The crystals can be rinsed with a mix of 50% water and denatured alcohol, also ice cold. A final rinse with ice-water makes them clean. Then let them
dry in contact with air. The salt is not hygroscopic at all, and it crystallizes well.
Now, how to make the explosive follows here:
Take 40 mg of this salt, crunch the crystals to a fine powder, and mix it with 10 mg of finely powdered red P. When 10 mg of this mix is ignited with
the flame of a candle, then a very loud BANG is obtained. I really was impressed.
Things become even more impressive if some of the red P is replaced by Al-powder.
This is an insanely powerful explosive. No need to confine the stuff, just a tiny heap of solid gives a loud bang.
I do not encourage anyone to make this mix in larger quantities, but it is fun to play with it in mg quantities. I have no idea about the
stability of the mix on storage, so please don't keep it around. Just make it and use it immediately.
The K3CrO8 looks as follows:
It is a peroxo compound of chromium in the +5 oxidation state. A better formula is K3[Cr(O2)4]. This peroxo compound keeps indefinitely, provided it
is kept in a dry place.
[Edited on 2-2-07 by woelen]
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Bert
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Is any greater effect obtained than that from chlorate and red phosphorous mixes?
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vulture
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I'd think that dichromate with red P would already give a nice bang...Care for a reference experiment? 
One shouldn't accept or resort to the mutilation of science to appease the mentally impaired.
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Sickman
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Woelen,
Do you get the impression that a true detonation takes place or is it simply a fast deflagration?
Perhaps, you could press a gram of it in a cap with a loose ignition charge and see if it has any potential as an initiator of a secondary
explosive.
Have you tried hitting it with a hammer to see if it is sensitive to impact?
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UnintentionalChaos
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Just out of interest, any idea how soluble the stuff is in water? I assume all the cold water is used because of a lower solibility, but I was mainly
interested because I can only get 15% peroxide and was wondering if that much excess water would cause a significant loss of product. Is it possible
that the remaining product could be precipitated with an addition of denatured alcohol?
Department of Redundancy Department - Now with paperwork!
'In organic synthesis, we call decomposition products "crap", however this is not a IUPAC approved nomenclature.' -Nicodem
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woelen
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@Bert: Yes, it is more powerful. KClO3/P burns very quickly, but it does not explode. The stuff I had even gives a loud bang (really impressive) with
just 10 mg of the powder, unconfined, on a little metal spatula.
@Vulture: I did the reference experiment with very finely powdered K2Cr2O7 and red P. This mix can hardly be ignited. Only if sufficient P is added,
it can be ignited, but then it is just burning of red P. When a little Al is mixed in, then it can be ignited somewhat easier, but it only burns
slowly with an orange flame and some bright yellow sparks. So, there is a huge difference between K2Cr2O7/P and K3CrO8/P. In contrast, the mix of
K3CrO8/P can very easily be ignited. Just keep it 5 cm above the flame of a candle and it immediately explodes.
@Sickman: I will do the hammer test, but I will not do the secondary explosives test. I will not make a gram of this material, the bang, produced by
that would be too alarming (I live downtown, with neighbours and don't want to create loud bangs outside). I'll keep you updated on the hammer test.
How can I distinguish between a true detonation and a very fast deflagration? I did get a real BANG.
@UnintentionalChaos: The very low temperatures are not because of solubility issues, but because of stability issues. If the temperature goes above 0
C, then there is a big chance of a thermal runaway in the reaction. I had that once, and had a fountain of hot strongly alkaline K2Cr2O7/KOH/H2O2 mix
and that is not fun at all.
I think that it also works with 15% H2O2. The material is not very soluble, just use a VERY concentrated solution of KOH and K2Cr2O7 and use a large
excess of KOH to make it really alkaline. Then I think you can get some of this compound with 15% H2O2.
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Rosco Bodine
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Have you tried a *small* sample contact / mixing test with sulfur ...then if no result , try adding a small bit
of water , or toluene , or glycerin ?
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nitro-genes
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"Things become even more impressive if some of the red P is replaced by Al-powder."
Does that mean it even makes a bang with flake aluminium powder in 10 mg quantaties?! That would be really something!
The fact that it makes a sharp bang means it goes supersonic, so in that sense is would be detonation. Though for powder mixtures it is usually called
deflageration, even when it goes supersonic. Aluminium/chlorate flashpowder can reach 3200 m/s under ideal circumstances though it is generally not
called detonation. The quantities in which it can go supersonic unconfined is amazing though for K2Cr2O8/P, I don't know any other pyrotechnical
mixture that can do this, with the possible exception of chlorates or permanganates + 1-3 micron Mg. The fact that it can detonate in these quantities
can only mean that it must be a very sensitive mixture, since the speed and acceleration of the reaction are greatly determined by the speed by which
the oxidator can release it's oxygen (decompose). So I wouldn't recommend making a gram of it anyway...
You could test the brisancy by lighting a 10 mg amount on an empty can of beer and see if it would penetrate the can... (safely behind protection with
ignition source on a stick)
[Edited on 3-2-2007 by nitro-genes]
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Nicodem
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| Quote: | Originally posted by nitro-genes
The quantities in which it can go supersonic unconfined is amazing though for K2Cr2O8/P, I don't know any other pyrotechnical mixture that can do
this, with the possible exception of chlorates or permanganates + 1-3 micron Mg. |
Looks like the decomposition of K3[Cr(O2)4] is quite exothermic or else such a rapid deflagration seems impossible. Woelen, have you tried to ignite
K3[Cr(O2)4] without any reducent? If truly exothermic the decomposition should propagate without additional heat. After all, even the decomposition of
H2O2 is quite exothermic, it is just the high activation energy that prevents it from explosively decomposing by itself. The complex with Cr looks
like it brings the activation energy of the peroxide decomposition down very dramatically (probably by the same SET mechanism as the Fe metal ions
do).
Nice and interesting discovery Woelen. Your experiments are always nice to read about. 
…there is a human touch of the cultist “believer” in every theorist that he must struggle against as being
unworthy of the scientist. Some of the greatest men of science have publicly repudiated a theory which earlier they hotly defended. In this lies their
scientific temper, not in the scientific defense of the theory. - Weston La Barre (Ghost Dance, 1972)
Read the The ScienceMadness Guidelines!
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YT2095
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I could be totaly wrong, but "Dragon eggs" springs to mind here, that has a very similar report in minute quantities also.
Just a thought
\"In a world full of wonders mankind has managed to invent boredom\" - Death
Twinkies don\'t have a shelf life. They have a half-life! -Caine (a friend of mine)
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woelen
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Accident with K3CrO8/Al + very small amount of P
Heating K3CrO8 without reducing agent results in quick decomposition (soft puffs, with slight hissing noise), giving yellow smoke and oxygen gas. Not
particularly violent. The yellow smoke most likely is K2CrO4. Be careful not to inhale that smoke, it probably is carcinogenic.
I had
an accident with my second experiment
I replaced 80% of the red P with Al-powder (German black) in order to make it more energetic (red P makes things easier to ignite, but also somewhat
less energetic and certainly less hot). I mixed this stuff in a thick Al-foil folded "cup" in order to avoid static discharge. But, despite of that,
suddenly it ignited with an intense white flame and a soft bang, while I had the Al-foil with the powder in my hand. After this, the Al-foil stuck to
my middle finger and now I have a deep burn of appr. 1½ cm² on my left middle finger. This is amazingly painful   and I hope to have a reasonable sleep tonight.
Fortunately, the mix did not burn through the thick Al-foil, so I do not have chromate contamination in my finger, I "only" have a burn. I also think
that I was lucky that the chems were not yet mixed very well, otherwise the burn would have been even hotter or I would have had a stronger explosion.
In total now I had appr. 100 mg of chems.
From this you can conclude, that this mix is not useful for the real work and I want to advice everyone to be VERY VERY careful with this, especially
if Al-powder is used as well. The hammer test is not needed anymore, even simple friction by mixing can ignite the material.
K3CrO8 is dangerous stuff!
[Edited on 3-2-07 by woelen]
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Levi
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Wow. Very interesting! You should look into getting a patent for that if it isn't already patented. I'm sorry to hear about your accident but I'd
love to see a picture of the burn Care to post one?
Chemcrime does not entail death. Chemcrime is death.
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Sickman
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Woelen,
Levi is right! You may have unwittingly discovered the next great bullet primer. However patents are rather costly! You may make a bundle of cash by
selling such a patent to a bullet manufacturing company, but first you must do the research and optimize the mixture's components and ratios.
Sorry to hear about your hand. I've heard applying a dilute solution of picric acid on the burn area may be helpful. I'm not sure exactly how it is
helpful (maybe it is a debriding agent), but at one time this was a common practice. Maybe just put some ice on it for a while and then some vasoline
and take an aspirin.
In the future adding an inert solvent could potentially make mixing ingrediants safer and them simply allowing the solvent to evaporate before use?
As far as knowing if the mixture detonates or deflagerates may be difficult with your present resedential situation. What I would do if it was me is
to press the mixture into a very strong pellet under some considerable pressure, in a sheilded loading fixture( a wooden block with some plexiglass in
front). This pellet when ignited will either deflagerate and any pop will not be as impressive as when the loose powder is ignited or it will produce
a sharp bang, indicating that the material does propagate a detonation front. It may not happen like that exactly as some primaries require
confinement for a true detonation to occur. In other words the pressing of a 2 grams of secondary into a cap and then 1.5 grams of the above mixture
also pressed then a loose amount of the same material on top and this loose material being ignited would be a true test of the mixtures initiatory
abilities. However like you said before, such a test is out of the question, so I'll leave it at that.
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The_Davster
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Interesting results, really sorry to hear of your finger. For bad finger burns I find falling asleep with my finger in a ice/water bath helps
imensely.
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chemoleo
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Very interesting!
From the first post onwards, I was convinced that peroxo chrome compounds are supposed to be blue!
I looked it up, and indeed, I remembered something different.
Cr2O7(2-), in the presence of H2O2 and *acid*, forms CrO(O)2, which is blue, and is still formally Cr(VI) (Jander & Blasius) .
So this is CrO5, so quite differnt to the compound that Woelen described
Since I am at it, it is made by
mixing cold HNO3 (or H2SO4) with dichromate, and ether is layered on top. To this, 2.5 mol/l H2oO2 is added and the mix is shaken. A blue colour
appears in the etheric phase, which is CrO5.
With pyridine and the evaporation of the ether, one obtains the solid pyCrO(O2)2. This reacts with Ag2O to pyridine and O2.
Looks like this compound cannot be isolated other than some Pi complex.
Anyway, this is a peroxo compound of chromium that always fascinated me. It would be way cool to get it into its pure state!
Regardless... it'd be really good to get a proper comparison to other primaries. Perhaps some members more astute in these matters would be willing to
do a little experimentation? Safely of course
Never Stop to Begin, and Never Begin to Stop...
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woelen
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Well, after a night of sleep the pain has diminished quite a lot already, but I still feel my finger all the time. I have been sitting in a chair,
with my finger in cold water and that relieved quite some pain, but as soon as I took out the finger, it quickly became very painful again (intense
burning sensation, which somehow spread out to the other fingers, although these have no burns).
It has a big blister on it and has to be treated carefully. I try to keep the blister closed, such that no dirt can come into the wound.
I consider continuing further experimenting with this material, but I'll not do the dry mixing anymore -- too dangerous. I've been thinking about
this. The red P probably made the mix I had yesterday very friction sensitive, and the Al made it burn exceedingly hot. That combination makes it
extra dangerous.
Water cannot be used as solvent for mixing, because K3CrO8 is not stable in aqueous solution, unless pH is very high (pH > 14 or so). At lower pH,
oxygen is evolved and an alkaline solution of K2CrO4 and KOH remains behind. At yet lower pH (pH < 7), a blue compound is formed, oxygen is
produced and on longer standing Cr(3+) remains in solution. I'll have to find a suitable solvent, which can be used safely with this compound.
@Chemoleo: There are three types of peroxo-chromium compounds.
1) Blue peroxochromates with structure (-)O-Cr(O2)2-(O2)-Cr(O2)2-O(-), summarizing Cr2O12(2-)
2) Red/brown peroxochromates with structure [Cr(O2)4](3-), with chromium in +5 oxidation state.
3) CrO(O2)2, deep blue, which forms adducts with many organic compounds, which have an :N or an :O lone pair.
Type (1) can be made by adding 30% H2O2 to a solution of K2Cr2O7, both liquids must be ice-cold. This type can be isolated, but it is not very stable
and it slowly decomposes in the course of a few days at room temperature.
Type (2) can be made, as described in my first post of this thread. It can be stored indefinitely (I have two samples, one sample more than 17 years
old (!!), and the other a few months old, both are equally active).
Type (3) I have never been able to obtain in any other state than transiently. I have no pyridine, and complexes with other compounds only have a
half-life time of minutes to hours.
| Quote: | | Perhaps some members more astute in these matters would be willing to do a little experimentation? |
Chemoleo is perfectly right with this. I'm not an explosives expert at all. For me, this little excursion into explosives was just an inorganic
chemistry experiment and not much more. It is interesting, but doing real research on its properties as primary is beyond my resources and also beyond
my experience/knowledge.
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garage chemist
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Related to the topic, what would the blue chromium peroxide (CrO5) that you can extract from acidified dichromate + H2O2 with Ether decompose into
when the ethereal solution is evaporated?
If it forms red CrO3 this would be a convenient preparation of this compound, which is otherwise not so easy to prepare (extreme hygroscopicity and
high solubility in water).
The ethereal solution could be dried before evaporating it, making the direct preparation of dry CrO3 easy.
I might try that out some time.
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Rosco Bodine
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woelen .....
a bit of safety advice here , and I don't know if you
were simply using the glass vial for photography and
then transferred the sample .....
but absolutely do not store unstable / unknown samples in glass because of the fragmentation hazard if the material should go off .
Use a poly sample container and don't fill it more than
about 10% full .....something like a few grams in the
bottom of a 120cc disposable polypropylene specimen container which is handled by its upper rim .
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BromicAcid
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Garage Chemist, I would worry about evaporating an ether solution of a peroxy compound too much to attempt this on any scale worth noting. It
definitely doesn't seem like the safest thing to do but it might work.
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woelen
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| Quote: | Originally posted by Rosco Bodine
woelen .....
a bit of safety advice here , and I don't know if you
were simply using the glass vial for photography and
then transferred the sample .....
but absolutely do not store unstable / unknown samples in glass because of the fragmentation hazard if the material should go off .
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Well, I stored the compound in a glass vial for many years already. Part of my K3CrO8 is 17 years old and still as active as when I made it. Recently
I made another batch and it looks exactly the same. This stuff can be made reproducibly and can be stored safely. At the time of making this material,
I of course studied its properties and also its stability. That is why I only isolated the K3CrO8 peroxochromate and not the blue K2Cr2O12, the latter
being too unstable for safe storage.
So, the peroxochromate itself is fairly safe, but a mix of this with strong reductors is dangerous, as I have experienced the hard way
@garage chemist: CrO5 in ether decomposes to a chromium (III) compound. I actually did try this. The solution at first is blue, but many hours later
it turns green, the typical color of chromium (III).
Also, making a concentrated solution is remarkably difficult. Just try it in water. Take 1% H2O2 with 1% HCl or H2SO4 and also add a 1% solution of
K2Cr2O7. You'll see an intense blue solution, but it only lasts for seconds.
Change all concentration to 0.1%. You still get quite a deep blue color, but the solution now remains blue for a much longer time.
Again change concentrations, now to 0.01%. You still obtain a clearly visible blue solution, and now it lasts even longer.
With somewhat higher concentration you even don't get the chance to have a lot of it absorbed in the ether layer.
Maybe if you work at -15 C, but at 0 C or so, it is not worth the effort.
[Edited on 4-2-07 by woelen]
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S.C. Wack
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I don't know if the authors were trying to slow down or accelerate decomposition here:
http://dx.doi.org/10.1016/0040-6031(86)85338-2
They also have 3 earlier articles on the heating of that cpd in that journal.
A couple years later, they got this published:
http://dx.doi.org/10.1007/BF00750020
Of course the chances of these containing anything of interest are not high, merely possible.
As woelen has already pointed out, this may put finely divided chromate everywhere, so its not surprising that there isn't a lot of research on its
explosive properties.
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woelen
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Do you have access to the full articles? I tried to open them, but a userid/password is asked, so I could not proceed.
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artem
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It's about the burning of pure K3CrO8(= K2CrO4+KO2+O2+q) and mixes, for example, at P=1bar mixture K3CrO8+20%Al2O3 with additives burns quite quickly:
pure 21.2+/-2.5mm/s
+rosin 24.9+/-4.1mm/s
+Teflon 18+/-3mm/s
+ZnO 16.2+/-3.5mm/s.
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garage chemist
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I read that ethyl acetate can also be used to extract CrO5 from aqueous solution. This would certainly be safer.
Woelen, would it be possible that the green color you observed upon standing of the blue extract was caused by a mixture of yellow (from dilute CrO3)
and blue (from remaining peroxide)?
Or did green Cr2O3 precipitate from the solution?
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woelen
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Hmmm... strange, they add non-oxidizing stuff to the solid? Why would you want that? Is this useful as rocket fuel?
I did a test with only sulphur added to the K3CrO8 as reductor, instead of red P and/or Al. This mix still burns amazingly fast. It does not give a
bang, but it burns very fast and makes a WHOOP noise when ignited. It burns fast like flash powder, however, with much less light (the light output
actually is quite low).
The K3CrO8/S mix also can be ignited very easily. Just keep it a few cm above the flame and it goes WHOOP. I did not make a really fine powder, I only
crunched the crystals of K3CrO8 with a little spatula, added some flowers of sulphur and swirled a little in a big pan in order to get the chems
mixed. I do no more crunching and mixing, while I have the material in my hands.
I also did a smoke analysis of the K3CrO8/S mix, by igniting some of this mix under a big beaker, capturing some smoke. The smoke, gives a yellow tint
to water, and on addition of acidified H2O2, the color is deep blue. From this it can be concluded, that the smoke contains chromate, which is NOT
good.
I also attempted to do a smoke test with the K3CrO8/P mix, but I only did this with 10 mg, due to the explosive nature (I don't want glass shattered
around). I could capture some smoke, but no chromate could be detected, not even with the very sensitive H2O2/acid test. So, with red P it seems that
(provided sufficient P is used) all chromium is converted to the +3 oxidation state and that is a good thing.
Altogether, the red P mix is more interesting than the S mix.
It is a pity that I do not have LiAlH4. I really would love to see what happens if powdered K3CrO8 is mixed with powdered LiAlH4 and then ignited.
That must be really spectacular . Of course only in mg quantities.
[Edited on 5-2-07 by woelen]
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