Sciencemadness Discussion Board

Chlorate

99chemicals - 18-6-2012 at 13:35

I have started some small scale fire works making. I have read that you should never mix chlorate and sulfur. It is supposed to make a very very sensitive mixture when mixed dry.

I have also read that chlorate and ammonium salts are also a no-no.

Does anybody know what happens chemically that makes those mixtures so hypersensitive and what the reaction equation is?

I would try it myself but I would not for fear of nothing happening.

[Edited on 6-18-2012 by 99chemicals]

woelen - 18-6-2012 at 22:46

Chlorate and sulphur is sensitive on its own. Even when the chlorate is 100% pure and the sulphur is 100% pure. In real life, however, the sensitivity of such mixes increases, due to formation of trace amounts of acid when sulphur is exposed to air. Sulphur reacts with oxygen and water, giving acidic sulphur compounds, which add to the sensitivity of sulphur/chlorate mixes. The amount of acid is very small (think of 0.01% or so), but it is enough to add to the sensitivity. Chlorate ion is much more strongly oxidizing in acidic environments than in neutral or alkaline environments.

A nice experiment is to carefully mix some powdered KClO3 and powdered sulphur, e.g. 100 mg of KClO3 and 40 mg of S, put this on a little pile and hit this with a hammer. A loud report is produced. DO NOT SCALE UP THIS EXPERIMENT!

Chlorate and ammonium ion is another thing. When these are mixed up, you get NH4ClO3, which is very unstable and easily decomposes in an exothermic reaction. Actually, this compound is so unstable that it may not be transported at all. In practice, this compound is not produced commercially. NH4ClO3 decomposes to mainly H2O, N2 and HCl, but some O2 and Cl2 can also be formed when it decomposes.

[Edited on 19-6-12 by woelen]

99chemicals - 19-6-2012 at 02:42

Quote: Originally posted by woelen  
Chlorate and sulphur is sensitive on its own. Even when the chlorate is 100% pure and the sulphur is 100% pure. In real life, however, the sensitivity of such mixes increases, due to formation of trace amounts of acid when sulphur is exposed to air. Sulphur reacts with oxygen and water, giving acidic sulphur compounds, which add to the sensitivity of sulphur/chlorate mixes. The amount of acid is very small (think of 0.01% or so), but it is enough to add to the sensitivity. Chlorate ion is much more strongly oxidizing in acidic environments than in neutral or alkaline environments.


Is the dilute acid making chloric acid? I know that is very nasty and could easily ignite sulfur, sugar, etc.

Thanks for the in depth reply Woelen.

woelen - 19-6-2012 at 03:34

Many people indeed say that the small amount of acid, present in sulphur, makes chloric acid with chlorate. Whether this is true or not, I leave unanswered. Most likely there is some equilibrium in which the acid from the sulphur is in equilibrium with chloric acid, but I'm quite sure that not all of it makes it to chloric acid. Fact is, however, that the acid sensitizes chlorate.

Btw, in my opinion, chlorate is not suitable at all for pyrotechnics. It not only forms very dangerous mixes with sulphur and ammonium salts, but also with all sulfides (e.g. Sb2S3, FeS), and with many finely divided metal powders (e.g. Al, Mg, Mg/Al, Fe). Perchlorate is your friend when you want to make nice fireworks, which are more safe (but still have an inherent risk). Sometimes, perchlorate mixes are hard to ignite though. I mixed KClO4 with Al-powder and was surprised how much heat was needed before this mix goes WHOOSH.

dann2 - 19-6-2012 at 05:44


Polythionic Acid, the "Trigger"

There is some reading on Sulphur + Chlorate problems here.

I belived K Chlorate + wax makes a nifty rocket propellent.
Sodium Chlorate is dangerous in fireworks. Potassium Chlorate no so bad (so long as you know the forbidden combinations).

caterpillar - 19-6-2012 at 13:58

Mixture of KClO3 with paraffin is not very sensitive. There are some another composition, based on KClO3- read "cheddite" tread at this forum. But generally perchlorates are better- due to their oxygen balance and smaller sensitivity.

99chemicals - 19-6-2012 at 17:09

Thanks.

I am not planning on using chlorate in my pyrotechnics(mostly black powder based compositions). I will try the micro scale chlorate sulfur this weekend.

Do sulfides have the same problem of making acids?

woelen - 19-6-2012 at 23:55

It depends on the sulfide. E.g. Na2S is very easily oxidized by air and forms all kinds of thionic acids, but FeS2 or Sb2S3 are air-stable. The latter, however, makes very sensitive mixes with KClO3. Not all problems with KClO3 are due to acid formation. KClO3 itself also is very sensitive when combined with certain reductors.

hyfalcon - 20-6-2012 at 02:22

As far as the initiation of the KClO4 and aluminum, add 2-3% Potassium Dichromate to lower initiation level. I was having to use my "fast" fuse to get my salutes to go off, after adding the dichromate, just regular fuse was all that was needed to get the flash to go off.

Mumbles - 28-6-2012 at 21:44

If you had to sensitize a KClO4/Al mixture to get it to ignite, you're doing something wrong, or have far too coarse aluminum.

I've met people who are willing to use chlorate and sulfur mixes in larger than experimental batches. These people I feel do not have the proper respect for the chemicals, art, or consequences. IMO, anyone willing to undertake these risks is either insane or Maltese (colored beraq are as close as you can get to assured accident). Chlorates and sulfur is generally more sensitive to impact, perhaps due to the low melting point. Lactose is also relatively sensitive to impact. Antimony trisulfide and chlorate is generally more sensitive to friction. There are sensitivity values in several books for actual data. Principles of pyrotechnics by Shidlovskiy, Chemistry of Pyrotechnics by Conkling, and F.A.S.T. by Shimizu come to mind.

I will agree with you on most accounts Woelen. However, there is a large area of pyrotechnics that does not involve metal fuels, ammonium compounds, or sulfur. Organically fueled stars are still commonly used, and have been used with a relatively good safety record. Chlorates are still required for good colored smoke stars and inserts.

The one usage of chlorates and sulfur compounds still in accepted use is for dark report mixtures. They are used to break a certain type of device known as crossettes. This is typically a mixture of chlorate and antimony trisulfide, as well as sulfur on occasion. They are used in quite small amounts, and it burns unexpectly mildly unconfined.

[Edited on 6-29-2012 by Mumbles]

hyfalcon - 29-6-2012 at 03:23

I've read about electric igniters being primed with antimony trisulfide and chlorate on a small gauge ni-chrome wire. It was then coated with nitrocellulose lacquer before any prime containing sulfur would be used to prime over the top. My question is, does the NC lacquer act as an effective shield to keep the chlorate from coming in contact with any sulfur containing compounds or should there be a layer of prime that doesn't contain any sulfur compounds?

Mumbles - 1-7-2012 at 00:20

I cannot speak to all electric matches. Of the ones I am familiar with made in the US, one is made withe a chlorate/antimony trisulfide mixture and then covered with BP and a NC or other coating. The other is made with a boron type mixture. Neither are terribly safe, especially to impact. A large number of the imported matches I've seen appear to be made with a lead salt of a poly nitrated aromatic species.

I have used both. I take precautions, but they're at least able to be handled for general use. I've seen both ignite based on direct impact however. There seems to be a trade-off between safety and sensitivity to electrical firing systems.

quicksilver - 1-7-2012 at 09:56

You're smart to take precautions.

I knew a guy who was NOT a dumb-shit but who used a material for E-matches that oxidized. It's not simply the element of a resistance wire that makes a good E-match but one that won't react (oxidize) with a chlorate, etc - that "set-up" a tragedy. Long story, short, he made good ones (in terms of visual design & initial functionality) but it became a nightmare. He had some drying and they caught a-flame in his kitchen when he was not home.
They were on tile so the damage was minimal but had he set them up or had them in another place he could seriously could have lost his home, pets, nice things for a few pennies of wire and a poorly thought out decision.

Mumbles - 2-7-2012 at 21:48

I obtained some experimental batches from the plant that produces the boron type. Over the course of about 2 years the nichrome wire had oxidized. It was detrimental in a functional manner, not in a dangerous manner as far as I could tell. Only 1 in 3 would ignite after that time.

In my mind one of the safest forms of electric match are those made in a bridgeless manner where the composition itself is both conductive and the pyrogen. There are sensitive and insensitive compositions that can be used. The insensitive versions have a noticable delay to ignition if a strong enough current is not used, but are otherwise approximately as sensitive as black powder. There are also pyrogen-less electric matches known as Talon or solar flare ignitors. These work alright, but do come with an undesired delay between pressing the button and the device firing.

As I said before there is a trade off between reaction time from the firing box and overall sensitivity of the match head. Most commercial matches come with a rubber or plastic sheath. This largely protects the sensitive part, though you still have to be careful. Some feel that to get the absolute best response from the firing system, you have to remove this sheath when fusing the device. I'd be lying if I said I have never done this, but it does always make me rather nervous.

Trust me, I know the consequences of being careless. I was in a hurry at one point, cut some corners, and paid dearly for it.

detonator - 31-8-2012 at 23:45

Potassium chlorate 85%;
Petrolatum (or other oils) to 10%;
Aluminum powder 5%.

Chlorate explosives, this ratio is less sensitive to the impact.
I even tried it refused explosion. Use HMTD detonated.