Potassium Chlorate Reaction Test: Sulfur

[Ubehage]

This guy makes videos where he mixes Potassium Chlorate with different chemicals, and shows how it reacts.

I was personally under the impression that Sulfur and PC would ignite instantly, which doesn't seem to be the case.

However, he also does explain why you should never mix these 2 substances: PC is extremely sensitive to sulphuric acid, which may be found in small amounts in pure sulfur.

 

Enough talk:

https://www.youtube.com/watch?v=2SfiPkdPbLM

[Arthur]

For private fireworks that are made and fired within a few weeks chlorate and sulphur is only a moderate risk, but for cheap (acid) sulphur and chlorate in commercial fireworks which may have a storage time in years and many cyclic humidity changes chlorate and sulphur mixes should be considered unstable, over sensitive and too dangerous.

 

In the UK Chlorate comps get special instructions in manufacture -including separate sheds and tools. Also Chlorate may not (by law) be used with sulphur or phosphorus.

 

The older supplies of "Flowers of sulphur" contained some acid impurities and this made it more hazardous than modern purer sulphur.

[lloyd]

I see that Arthur responded first, but I'll continue, anyway.

 

That's really not the case, Ube. If you use the (essentially chemically-pure) "Rubber makers' sulfur", there are virtually NO decomposition products in it. In fact, it has no discernible odor or reaction to potassium chlorate, except in the following conditions:

 

1) KClO3 and sulfur ignite at a much lower temperature than other mixtures. This may be because of the low melting temperature of sulfur, but also because of it's particular valences, etc.

2) KClO3 and sulfur form an IMPACT AND FRICTION SENSITIVE mixture.

 

Neither even implies that it would 'ignite on contact'. Even modern "flowers of sulfur" is pure, compared to times past. The dangers of Chlorates and Sulfur are over-stated, even though they exist to a greater degree than with other oxidizers.

 

In times past, sulfur was purified by a hot-distillation process which vaporized the sulfur, then allowed it to condense as a fine powder. The process yielded some decomposition products. Among them was sulfurOUS (not sulfuric) acid. That component aggravates the sensitivity of the mixtures containing it.

 

LLoyd

Edited March 1, 2017 by lloyd

[Ubehage]

I see that Arthur responded firs, but I'll continue, anyway.

 

That's really not the case, Ube. If you use the (essentially chemically-pure) "Rubber makers' sulfur", there are virtually NO decomposition products in it. In fact, it has no discernible odor or reaction to potassium chlorate, except in the following conditions:

 

1) KClO3 and sulfur ignite at a much lower temperature than other mixtures. This may be because of the low melting temperature of sulfur, but also because of it's particular valences, etc.

2) KClO3 and sulfur form an IMPACT AND FRICTION SENSITIVE mixture.

 

Neither even implies that it would 'ignite on contact'. Even modern "flowers of sulfur" is pure, compared to times past. The dangers of Chlorates and Sulfur are over-stated, even though they exist to a greater degree than with other oxidizers.

 

In times past, sulfur was purified by a hot-distillation process which vaporized the sulfur, the allowed it to condense as a fine powder. The process yielded some decomposition products. Among them was sulfurOUS (not sulfuric) acid. That component aggravates the sensitivity of the mixtures containing it.

 

LLoyd

Thank you for clearing these things up, Lloyd.

Pretty important to know exactly what we're talking about in this hobby.

Edited March 1, 2017 by Ubehage

[Arthur]

One of the old London fireworkers is recorded as hanging two chlorate/sulphur crackers on his wall and then some months later they got wet and got dried in weather. They DID spontaneously explode doing lots of damage. The reason for the explosion was said to be the dampness dissolving chlorate and then the drying let crystals form inside the surface of the sulphur, along with the limited purity of ingredients available at the time.

[lloyd]

"Limited purity" is the key phrase. Rubber Makers' sulfur is quite pure, and even from China, most of the Chlorate we can obtain is quite pure, also.

 

Yep... I remember reading that account (somewhere -- I think Mike S quoted it. Don't make me search my memories. They're not as good as once!)

 

Lloyd

[Arthur]

The UK regulatory arrangements make chlorate mixtures difficult, but they are essential for some things. Having a separately clean place to work is good, having separate tools is good too, it saves chlorate being transferred into other mixes where you don't want it or expect it. IMO there is no real way to clean a ball mill free of chlorate, or a (set of) sieve.

[lloyd]

Agreed. In fact, in my communications with some British manufacturers, I've seen that they wish the regulations could be relaxed some, in light of the purity of modern chemicals.

 

Lloyd

[Arthur]

With the UK having ZERO incidents in fireworks storage there is a call for looser regulation of storage but it's unlikely to happen! The problem with chemicals in the UK is that the market is small so a pallet load being imported gets split several ways so very rapidly all forms of ISO9001 traceability gets lost then no-one knows what the purity of any bag is.

 

I've seen lots of sulphur coming from the refinery industry. Makes low sulphur petrol and diesel available too.

[DavidF]

Additionally: heating sulfur so that it melts causes it to volatilize to some degree. The sulfur vapor in the air then becomes oxidized. Burning sulfur causes it to form sulfur dioxide. The sulfur dioxide combines with natural moisture in the air to become sulfurous acid. The sulfurous acid then becomes oxidized to form sulfuric acid.

 

What's the point of knowing that? Well, if you have 'non-acidic' sulfur in a mixture, and store it in a magazine that gets hot inside, the sulfur can actually become acidic. If you dry black powder-based stars in the hot sun- which you shouldn't do anyway, for other reasons- sulfur can volatilize from the stars. The fact that you can smell it is proof that this is occurring. So, sulfur that is non-acidic can become acidic, and that acid can become sulfuric acid.

 

Sulfur 'burners' used in greenhouses make use of this fact. They heat the sulfur, which causes some of it to vaporize. It is NOT burning. If it was burning, it would produce too much sulfur dioxide, which is quite toxic. The vaporized sulfur in the air oxidizes to sulfur dioxide, which becomes sulfurous acid, and ultimately sulfuric acid. The micro-deposition of sulfuric acid on the leaves of plants alters the pH of the leaf surfaces, preventing or killing molds and mildews.

 

These are minor points I bring up, sure. But, to say that using non-acidic sulfur absolutely guarantees that no spontaneous reactions will occur would be incorrect. Storing chlorate-based stars containing sulfur and natural moisture in a magazine that has extremes of temperature could create a problem.

 

One thing the video didn't show is that mixing potassium chlorate and sulfur and igniting it while confined will cause a heck of a boom!

[lloyd]

But David,

The one thing the UK enjoys that we don't in most of the USA is that the 'summers' there are like our early Springs and Falls!

 

Lloyd

Edited March 2, 2017 by lloyd

[DavidF]

That's true! But most of the folks reading this are not in the UK.

[lloyd]

L