Reactivity of (per)halates, a comparison

[woelen]

I have done a lot of experimenting last two weeks with all kinds of halates and have investigated how fast they react, when mixed in a pyrotechnic mixture.

 

I have access to the following ones:

 

potassium chlorate, KClO3

potassium perchlorate, KClO4

sodium perchlorate, NaClO4

potassium bromate, KBrO3

potassium iodate, KIO3

potassium metaperiodate, KIO4

sodium metaperiodate, NaIO4

 

Of one of these (KIO4) I have made high speed movies with a digital camera, see thread http://www.scienceforums.net/forums/showthread.php?t=20936 .

 

What I have observed is the following order of reactiveness with red P.

 

KBrO3 > KClO3 >> KIO4 ≈ KClO4 >> KIO3

 

KBrO3 is slightly more reactive than KBrO3. This is so reactive, that a mix of KBrO3 and red P cannot be made safely. The same is true for KClO3 and red P. These, however, can be mixed, but that must be done VERY carefully. In many cases the mix explodes/ignites on mixing. A mix of KBrO3 or KClO3 with red P gives an explosion when the chemicals are mixed.

 

Both KIO4 and KClO4 can be mixed with red P without problem. I never had an unexpected explosion while mixing, so this mix is less sensitive. However, on heating, the mix explodes. This also is shown by the video, given in the other thread.

 

With KIO3, the mix does not explode. It burns with a whoosh sound and gives purple smoke. It burns quite fast, like black powder, made of KNO3/C/S.

 

I have also done experiments with the anhydrous sodium salts NaIO4 and NaClO4 and red P. These seem to be somewhat less reactive. This surprises me, because I expected the same effect as with KIO4 and KClO4. NaClO4 is somewhat hygroscopic, but NaIO4 certainly is not. Apparently, the ions are attached somewhat stronger to the (smaller) sodium ions. Still, with these, an explosion can be obtained.

 

With sulphur, KBrO3 is very violent. It does not explode, but gives a very bright white flame and it burns very fast. With KClO3, the mix also burns very fast. With KIO4 and KClO4 the mix burns, but I had some difficulty igniting it. It is much less sensitive than the same mix with KBrO3 and KClO3. A mix of KIO3 and S hardly can be called a pyrotechnic mixture anymore.

 

These are interesting observations. Are there any others, with similar observation with other oxidizers and/or other reductors. It would be nice to have a kind of roundup on many oxidizer/reductor combinations.

 

I also noticed that for the red P mixes somewhat larger quantities (still only 10 ... 15 mg of mix) usually result in a high-pitched loud explosion, even when the powder is not confined, while at lower quantities there is a kind of low WHOOSH sound, close to explosion, but not as nearly as loud as the high-pitched explosion. Appaently, even unconfined powders can exhibit a form of self-confinement. Is this because the reaction proceeds faster, than that the gasses/smoke can be expelled from the mix?

 

If someone wants to repeat these experiments, please be careful and do not use quantities larger than 25 mg or so. With 25 mg the bang can be very loud already and the flash of fire can be really hot. So, be careful, especially when mixing the chems. Never mix larger quantities at once, limit the mixing to quantities of 25 mg total stoichiometric mix.

[YT2095]

I concur with everything you`ve stated thus far barring the Bromate tests, I`m still waiting to get my electrodes for that.

as discussed in PM some time back, the rp is a Very good reducer, the observations of 2 solids reacting in such a way are Very contra-intuitive!

 

it may be an idea also, with 2mg (and no more than 5mg) to do impact (drop tests) and obtain results also.

I find these are usefull for determining sensitivity with even the most seeming "inert" mixtures.

 

X weight at X height dropped under gravity.

 

a hammer on a hinge bolted to your desk with a tape measure`s ok if you want to be REALLY Cheap