Sciencemadness Discussion Board - Unreactive properties of KClO4?

Unreactive properties of KClO4?

woelen - 9-9-2009 at 12:22

I have done quite a few experiments with Mg(ClO4)2, NaClO4 and also some with HClO4 and now I have quite some waste, containing perchlorate. I worked up the waste with KCl and made KClO4 from it (which actually is surprisingly easy, it dissolves well in hot water, while being almost insoluble in cold water) and recrystallized twice from distilled water. I now have some pure KClO4, a snow-white crystalline solid, which easily can be crunched into a white powder.

I just wanted to make a pyrotechnic mix of this KClO4 with sulphur just for the fun of it (nice demo for kids), but to my surprise this mix cannot be ignited

and the kids were very disappointed. I mixed 2 parts of KClO4 with 1 part of sulphur (appr. stoichiometric ratio for KClO4 + 2S --> KCl + 2SO2). But even when some of the mix is kept on a spatula inside the flame of an alcohol burner, this mix does not ignite! The sulphur melts and fizzles somewhat and becomes dark yellow and that's all.

I am a noob in the field of pyrotechnics, but this is not what I expected. If I make a similar mix from KClO3 and S, then the mix very easily ignites and the ratio is not critical at all.

When I add a little amount of red P (just 1% or so) to the mix of KClO4 and sulphur, then it can be ignited easily, but I do not like to use my red P in pyro-mixes as red P is too valuable to be wasted for such things.

What are your experiences with KClO4? Do you also have difficulties igniting mixes with this chemical?

[Edited on 9-9-09 by woelen]

1281371269 - 9-9-2009 at 13:23

67% KClO4, 33% Al is supposed to be a good mix. Also KClO4 with sugar.

Jor - 12-9-2009 at 16:43

I have no experience with pyro, but I do remember that I once mixed a small amount of KClO4 with red P. It was no more than 100mg of mix. Even when a few mg are ignited you get bright flashes. Really amazing. Really fun stuff I can recommend, although stay under 100mg, as the mix is really powerful.

That's the only thing I have done with KClO4. I find it a rather useless chemical, as I don't do pyro (like once a month with a 100mg amount, thats all).
I wish I had NaClO4, wich is much more interesting.

[Edited on 13-9-2009 by Jor]

woelen - 12-9-2009 at 22:53

I also tried the mix of Mossydie, but that also cannot easily be ignited. Even when kept in the flame of a propane torch, it does not ignite. After that, I tried a somewhat modified mix, taking 130 mg of finely ground KClO4, 35 mg of 2000 mesh Al-powder (so-called German dark) and 10 mg of sulphur. This mix still is hard to ignite, but when it goes, it goes BLITZ. I then prepared the same KClO4/Al/S mix, but now also added 2 mg of red P. When this is done, it still is very powerful and flashing, but now ignition is very easy, just keep it near the flame of an alcohol burner, not even need to keep it in the flame.

Based on this, I come to the conclusion that KClO4 is a powerful oxidizer, but you need quite some heat in order to ignite mixes with this, just like with thermite reactions. When even a tiny amount of red P is added, then it can easily be ignited, probably even so easily that the mix becomes dangerous to keep around.

densest - 13-9-2009 at 16:53

***DANGER**** KClO4 and P deflagrates/close to detonates on NO provocation. It is what pyrotechnics people call a "death mix".

KClO4 and finely powdered Al (or Mg, or Zr) burns at a rate close to the DDT (deflagration/detonation transition). More than 50 mg in a container with a fuse without a license in the US is a felony and actively pursued by the DHS, etc.

Adding S to KClO4/Al sensitizes it significantly.

Most of the "fireworks factory explosions" in the news over the last 10 years have involved large quantities of KClO4/Al mix (flash powder). It is sensitive to friction, heat, spark, and chemical stimulus.

Mix up 10-20 mg of perchlorate/p and tap it with something metallic. It will go BANG.

Mixed with fuels like red gum it makes a very good pyrotechnic color base.

[Edited on 14-9-2009 by densest]

ketel-one - 13-9-2009 at 17:17

Zinc seems nice because it's super obtainable. Just broke into couple alkaline batteries, trying to do this experiment: http://woelen.homescience.net/science/chem/exps/bleach/index.... If I can really obtain NaMnO4 from MnCl2 +NaOCl that would be something. Although I guess it's a weaker oxidizer than KClO4 seeing as Mn is much easier put into that oxidation state than Cl.

_{EDIT(woelen): Changed link, so that it works again.}

[Edited on 6-5-14 by woelen]

woelen - 13-9-2009 at 22:50

@densest: Yes, I agree with your observations that KClO4/Al is a very powerful flash mix, but what I observe is that it is not easily ignited at all. I tried the KClO4/P mix and it burns violently, but it does not set off when tapped. Maybe if hammered, but I did not try that,
I also tried KClO3/P and that is extremely sensitive. I have a demo on my website of the sensitivity of this mix, just tapping 10 mg or so with a glass rod (not heavy banging, just tapping) leads to explosion.

http://woelen.homescience.net/science/chem/exps/raw_material...

Are you sure that in some cases you confuse the properties of KClO3 with those for KClO4? KClO4 does make powerful flash mixes, but my experience is that mixes, based on KClO4 need quite some heat before they ignite, even when sulphur is present.

@ketel-one: That demo is nice for showing how bleach can oxidized manganese to oxidation state +7 but it is not useful for preparation of permanganates. What you see in that experiment is a very very dilute solution of permanganate, even a 1% solution already is nearly black. Its color is very intense. Besides that, isolating NaMnO4 from a solution is more or less impossible if so many other impurities are present. Lookup the thread on making permanganates over here. Member "Der Alte" has done a lot of experiments in this area and what he has written on the subject is a good read.

JohnWW - 14-9-2009 at 00:39

Quote: Originally posted by woelen

(cut)
@ketel-one: That demo is nice for showing how bleach can oxidized manganese to oxidation state +7 but it is not useful for preparation of permanganates. What you see in that experiment is a very very dilute solution of permanganate, even a 1% solution already is nearly black. Its color is very intense. Besides that, isolating NaMnO4 from a solution is more or less impossible if so many other impurities are present. Lookup the thread on making permanganates over here. Member "Der Alte" has done a lot of experiments in this area and what he has written on the subject is a good read.

Household bleach (alkaline) can, similarly, also oxidize Fe(III) to magenta-colored ferrate(VI), but again it is practically impossible to isolate any solid sodium ferrate(VI) from it.

chloric1 - 14-9-2009 at 12:55

@woelen I had simular problems with ammonium perchlorate and sugar mixes. They ignited very easily but burned white hot and REAL SLOW. My solution was to mix potassium nitrate with sugar and add it to the perchlorate mix and it burns with a ROARING noise! Chlorates would be too dangerous as additives so I recommend the nitrates as your heat booster.

densest - 15-9-2009 at 17:48

@chloric1 - NH4ClO4 is (in)famous for slow decomposition. Many different catalysts work to speed it up a lot: K2Cr2O7 is very effective, MnO2 is good, even extremely finely divided Fe2O3 works some. Small perchlorate particle size is very important to fast combustion.

@woelen - I've read hypotheses that one reason KClO3 mixes ignite more easily than KClO4 is the presence of various unstable decomposition products. How fine is your KClO4 powder? The physical shape of the aluminum powder makes a big difference in activity - flake is far more active than spheres. It's sometimes hard to ignite KClO4/Al with a flame because it's either very reflective or transparent so radiant heat energy just bounces off. Touch it with something above 400C and ignition is pretty much instantaneous. Yes, KClO3/P is -incredibly- sensitive, but back when I had access to red P I tried a pinch of KClO4/P and it went off with a tap. Now, the P was old and so was the perchlorate, so contaminants like white P and chlorine oxides could have sensitized it. Your brand new pure perchlorate may be less active

ketel-one - 15-9-2009 at 22:08

Quote: Originally posted by woelen

That demo is nice for showing how bleach can oxidized manganese to oxidation state +7 but it is not useful for preparation of permanganates. What you see in that experiment is a very very dilute solution of permanganate, even a 1% solution already is nearly black. Its color is very intense. Besides that, isolating NaMnO4 from a solution is more or less impossible if so many other impurities are present. Lookup the thread on making permanganates over here. Member "Der Alte" has done a lot of experiments in this area and what he has written on the subject is a good read.

Right, I don't actually need permanganates, but outside of using a little in chemistry class to test for something I forgot what I've not handled them very much, so this is just experimentation. I love your site btw.

I assume everybody understands why KClO4 is more stable than KClO3, although I've never quite understood how KNO3 decomposes. KNO3 = KNO2 + .5O2 doesn't seem very oxidizing.

woelen - 15-9-2009 at 22:41

KNO3 is oxidizing, because it can give up almost all of its oxygen. It goes further than KNO2. If e.g. a mix of potassium nitrate, sulphur and carbon is ignited, then the main reaction is oxidation of carbon to CO2 (or to K2CO3, but that is the same oxidation state) and sulphur is oxidized to SO2 (and also some end up even more oxidized as K2SO4). The bigger part of the nitrogen leaves the burning mix as N2.

Formally you could write: 2KNO3 --> [K2O] + N2 + 5[O]
But keep in mind that this is just a purely formal equation. It does not happen on its own (that's why I write [] around the K2O and O), in reality, the K2O and O ends up in K2CO3, K2SO4 and K2SO3). This formal equation does show, however, that 5 out of each 6 oxygen atoms is available for oxidation.

[Edited on 16-9-09 by woelen]

Formatik - 30-9-2009 at 14:03

Quote: Originally posted by woelen

I just wanted to make a pyrotechnic mix of this KClO4 with sulphur just for the fun of it (nice demo for kids), but to my surprise this mix cannot be ignited

This is probably why some early references describe the perchlorate as an being inferior oxidant than chlorate, e.g. Leitfaden der Pyrotechnik (1899) mentions it.