Pyro-related -- why not use KBrO3 as oxidizer

[woelen]

I'm wondering why all those people want to make KClO3 as oxidizer for pyrotechnic compositions. NaClO3 can be made in electrolysis cells from NaCl and then be precipitated out as KClO3.

 

I have done some experiments now with NaBr, instead of NaCl and I was really nicely surprised to see how easily one can make KBrO3 from this!

 

Electrolysis of NaBr has quite some advantages over electrolysis of NaCl.

1) No trouble with gaseous chlorine gas, which corrodes all things like hell in the neighborhood of the cell and also inside the cell. Any bromine formed remains in solution, it sinks to the bottom and does not bubble. Sometimes the cell contents need to be mixed well in order to bring hydroxide from the cathode region to the bromine in the anode region.

2) The reaction, in which bromate is formed is almost instant. Chlorine gives hypochlorite, bromine gives hypobromite, but the latter VERY easily disproportionates to bromide and bromate. The cell does not need to be warm.

3) This is a very important one: My graphite anode hardly is corroded (pulverized) by the electrolysis process. Bromine comes off as liquid and no small graphite particles come in the liquid. This is something which I really like .

 

When electrolysis is allowed for a long time, then at a certain point you'll see that quite some gas is produced at the anode as well. Then it is time to stop. This gas is oxygen and if that is produced in appreciable amount, then it means that most bromide is used up and bromate is formed.

 

Potassium bromate can easily be precipitated from the liquid by adding potassium chloride solution. KBrO3 is only sparingly soluble, just like KClO3. One-time recrystallization gives purer KBrO3. The sodium otherwise may be a problem in compositions where color is required.

 

Finally, NaBr is cheap. You can get it at a price tag of a few dollars per pound, when purchased in kilo quantities at technical grade quality.

 

Why isn't this process used more in home-brew pyrotechnics? I personally did some experiments with KBrO3 as oxidizer and I must say, it is powerful, comparable to KClO3. I'm not sure about its long term sensitivity and stability though in compositions. KBrO3 itself, however, has excellent shelf life, it is not hygroscopic at all and crystallizes very well from aqueous solution.

 

If someone can shed some light on this and on the usefulness of KBrO3, then I would be pleased.

 

One remark: If you intend to repeat my experiment, please keep in mind that bromate might be carcinogenic. In the past it was used as a food additive in cakes, bread and so on, but that use is abandoned since the 80's.

[RyanJ]

Hmm, if its cheep and its powerful there must be a good reason why its not used, I'm shure YT has the answer to this one!

 

Could it be there is a toxic product of the reactions that stops them using this? I mean some of the stuf from todays fireworks no oubt are but maybe there is a carcenogenic or some cumulative toxin produced as a result of the reaction(s)?

 

Cheers,

 

Ryan Jones

[akcapr]

Well, he said the bromate could be toxic. During the reaction is any elemental bromine formed or is all just oxidized to ions?

[Skye]

I'd guess the main reason that the chlorate is used is because table salt is so easy for people to get.

[jdurg]

The presence of chlorine, in the form of an ion or an organically bonded atom, greatly intensifies the color of a pyrotechnic display. Hence why PVC is sometimes added to a mixture. By using a chlorate as an oxidizer, you already have built in a good deal of chlorine into your mixture so you won't need to add nearly as much 'extra chlorine'. If you were to use a bromide/bromate, you'd lose that added intensity from the chlorine. As a result, you'd need to add chlorine in some other manner. This adds more weight to your shell which means a bigger charge is needed to lift it off the ground which means more money.

 

In addition, it is believed that bromide and other bromine salts have a sedative effect on humans and a depressive effect on sex drive. While I'm not sure about the validity of that, if indeed that is correct then you don't want massive quantities of bromine salts out there. Though I'm pretty sure that it's the color enhancements of chlorine that cause chlorates to be preferred.

[YT2095]

have a look here: http://www.sinarkimiautama.co.id/potassium_bromate%20-%20msds.html

 

did you notice the Toxicity and the fact it`s Shock sensitive (the molecule size of the bromine holding the Oxygens makes it unstable like that).

however it is used in some pyro comps.

[woelen]

The argument of bromide toxicity seems fairly meaningless to me. Bromate is reduced to bromide and if some bromine were formed, then that is converted to bromide really fast under normal conditions. The average piece of fireworks contain barium salts for color, copper salts for color, chromates or dichromates for Mg-coating, and who knows what more. Then a little bromide does not seem a real concern to me. Bromide only is marginally toxic.

 

The argument of NaCl being so easily accessible truly is a valid one. But, if one is looking a little bit further, then NaBr also is easy to find (swimming pool supplies, photography raw chemical shops and not to forget eBay at some times). The somewhat more serious pyrotechnician is not held back by this, such a person also has other harder to find chems, so why not get some NaBr? I have experienced that it is easier to make bromate than chlorate, due to much smoother reaction of hypobromite to bromate and due to the anode not being pulverized as quickly as with chloride electrolysis. The latter phenomenon is a real pain in chlorate production.

 

The color part might indeed be the most important reason. But, does bromine not enhance color? Well pyrotechnicians, jump on this thread and show us what you know about this .

 

Ah, while I was typing YT jumped in . Yes, I have seen the MSDS of KBrO3 also, but as I noted, toxicity of other pyro-chems sometimes is even worse. Heavy metals are not broken down, bromate and bromine are destroyed very quickly under outdoors-conditions and I expect their chemical halflife to be only in the order of hours, when coming in contact with soil, natural waters, etc. The reaction product will be bromide.

 

With regards to stability, I have some of the stuff right now, and it is quite stable. KBrO3 on its own cannot be made to decompose violently. Even when it is hit with a hammer, nothing happens. On heating with a propane torch directly on the solid apparently nothing happens, but it looses its oxygen, making KBr. When treated with concentrated H2SO4, then O2 and Br2 are released in a vigorous bubbling reaction (somewhat like when H2SO4 is added to solid NaCl), no bromine oxides are formed.

Mixes of KBrO3 and reductors indeed are quite sensitive. I made a few batches of 100 mg of KBrO3/S mix and wow, that stuff is energetic, it flashes with a bright greyish/purple light and then it is gone! It does not explode, however. I have the impression that KBrO3 mixes are more energetic than corresponding KClO3 mixes. Unfortunately I dare not light some larger batches, due to the very strict regulations on pyro in the Netherlands (but Dec 31 is coming, that gives a little more headroom for just one day). I also do not dare to store KBrO3/S mixtures, due to my lack of knowledge on stability of that kind of mixes. I mix the stuff in-place and burn it immediately.

[YT2095]

it`s really only ever used in Exploding compositions, it`s far to sensitive and violent to be used in any other than this, whereas Chlorate (often replaced now with Perchlorate for stability reasons) can be used in a wide variety of places in a firework from the salutes (exploding) to the rocket engine grain, and in the stars and gerbs.

you only need to order the one Oxidiser to do all these things.

 

if you maufacturing line was all one type of firework like FireCrackers KBrO3 is fine as it`s only good for violent reactions, but even then, you`de still need fuse that was compatible.

[woelen]

it`s really only ever used in Exploding compositions' date=' it`s far to sensitive and violent to be used in any other than this, whereas Chlorate (often replaced now with Perchlorate for stability reasons) can be used in a wide variety of places in a firework from the salutes (exploding) to the rocket engine grain, and in the stars and gerbs.

you only need to order the one Oxidiser to do all these things.

 

if you maufacturing line was all one type of firework like FireCrackers KBrO3 is fine as it`s only good for violent reactions, but even then, you`de still need fuse that was compatible.[/quote']

Ah, I see. So we can conclude that KBrO3 is not very versatile and indeed is not that interesting from a pyrotechnic point of view ? I indeed noticed that it is very violent in its reactions, as I wrote above. Still, making this stuff is fun on its own. Any ideas for other nice applications of KBrO3 in a home lab?

 

Btw, YT, you have seen commercial KBrO3? My stuff is very pale yellow, almost white, but I expected it to be purely white, like clean KClO3. Or is it normal that bromate has a very faint yellow color? The MSDS's decribe it as a white crystalline solid, but of course, they are not that precise and very light yellow may also be white in an MSDS.

 

I also made silver bromate in small amounts, simply by adding a hot solution of KBrO3 (in cold water it hardly dissolves) to a solution of AgNO3. This gives a white precipitate of AgBrO3, which quickly settles at the bottom and easily can be isolated. That precipitate indeed is purely white, like fresh snow. That must be a hell of an oxidizer, but I did not yet try that, due to fear of a real explosion.

 

Finally, do you think that Ag(NH3)2BrO3 is stable? That would be a really energetic compound, with its oxidizer and reductor in one compound in precisely the good ratios: Ag(NH3)2BrO3 --> AgBr + N2 + 3H2O. I have read that it can simply be made as a white precipitate by adding a bromate solution to an ammonical silver solution, which contains the complex ion [Ag(NH3)2](+). But, how safe is that? You seem to know quite some things about pyro-related chemistry, could you elaborate on this?

[YT2095]

ammoniacal silver compounds can be extremely dangerous, even something simple like Tollens reagent can form explosive compounds given time, in fact Certain compounds have claimed many lives (buy accident) in the past

it will detonate even when wet!, although dissolved in Ammonia, it`s reasonably stable, miligram quantities can remove finger tips!!!!

 

as for Lab applications, I can`t really think of any, but neither can I for your TACN other than keeping it as a "Sample" to say you have some

 

as for Silver Bromate, again, be very carefull, it WILL detonate propper! and with little provocation, it needn`t have a reducer there either IIRC.

 

btw, this is stepping WELL OUT of the Pyro area here, into very dangerous ground, and bordering our Rules line. think Ammonium Chlorate here, then add a molecule (a large one) such as Silver as the "Hinge Pin" that holds the lot together, you`re smart enough yourself to work out what the outcome would be

[woelen]

ammoniacal silver compounds can be extremely dangerous' date=' even something simple like Tollens reagent can form explosive compounds given time, in fact Certain compounds have claimed many lives (buy accident) in the past

it will detonate even when wet!, although dissolved in Ammonia, it`s reasonably stable, miligram quantities can remove finger tips!!!![/quote']

Please, do not overreact on this one ! Ammoniacal silver compounds indeed can form fulminating silver compounds, but they only are formed at longer times of standing and from solution species. Indeed, if they are formed, you have a BIG problem. I have made ammoniacal silver solutions quite often and I work comfortably with them. The only thing you should not do with them is store them. Use them immediately after preparation.

 

 

as for Lab applications, I can`t really think of any, but neither can I for your TACN other than keeping it as a "Sample" to say you have some

Lab application of what? I asked for the potassium bromate, not for the silver fulminates. I'm a little bit confused here.

 

as for Silver Bromate, again, be very carefull, it WILL detonate propper! and with little provocation, it needn`t have a reducer there either IIRC.

What could be the mechanism behind that? I doubt whether this can detonate without an oxidizer. I'll give it a try by making some and hitting it with a hammer. An another option is to heat it with a propane torch. Don't worry, I'll do this with only a few tens of mg.

 

btw, this is stepping WELL OUT of the Pyro area here, into very dangerous ground, and bordering our Rules line. think Ammonium Chlorate here, then add a molecule (a large one) such as Silver as the "Hinge Pin" that holds the lot together, you`re smart enough yourself to work out what the outcome would be

I asked these things just out of curiousity. I only wanted an opinion on the compound Ag(NH3)2BrO3. I do not agree with your comparison with ammonium chlorate. Here I'm talking about a complex of ammonia, not ammonium. I cannot imagine a compound, made of ammonium chlorate and then silver hinged in somewhere. The compound, I'm talking about contains ions [Ag(NH3)2](+) and BrO3(-).

Of course, I agree with you that this might be a really dangerous compound.

 

YT, if you think that this is going over the edge of SFN's rules, then I'll stop with this discussion and I'll respect the rules. In that case, feel free to remove this part of my response or edit my response. I'll wait and see what remains of this thread .

[YT2095]

an Idea occured to me while thinking about my post in the purple Gold thread, silver Bromate Should be Light sensitive too, I know the Chlorate is, and that bromides are used in photography, it Might worth testing this

 

the reasoning behind the silver bromate as an explosion risk, is that KClO3 can detonate (in fact it was used in ww2) silver salts are far more easily reduced than group 1 types, and when you consider that Bromine is a larger molecule also than Chlorine, it`s stability is lowered again.

so based on that, I`de tend to be especialy carefull when dealing with it until it could be tested, I`de certainly expect a *Bang* if you mixed in some fine glucose and did your "Hammer Test".

 

it might be worth you making a rig with a known weight (say 1Kg) on a runner with height markings on it, so you could use that to compare results of impact sensitivity

[woelen]

Now I did another nice experiment with halogenate ions. I recently purchased a kilo of NaI (sodium iodide). I did an electrolysis experiment with this, in an attempt to make iodate. This also works well, although it is a little bit more messy than making KBrO3.

 

Dissolve NaI in water and electrolyse with a graphite anode and a metal cathode (but graphite is even better in order to prevent metal contamination). At the anode, a heavy brown compound is formed. This is iodine, which dissolves in the iodide solution. Also some solid iodine is formed (turbidity), but this quickly dissolves on shaking.

 

When this process is allowed to run for a while, then around the anode, the liquid becomes really dark brown and heavy stuff sinks to the bottom. With shaking, however, the liquid quickly becomes light yellow again. No oxygen is formed at the anode. At the cathode, hydrogen gas is formed.

 

The voltage, which needs to be applied is quite low (somewhere between 4 and 5 volts). When too high a voltage is applied, then oxygen gas is formed at the anode besides iodine, and the anode pulverizes in that case.

 

When the electrolysis is running for a very long time, then oxygen is formed anyway at the anode, indicating that the concentration of iodide is dropping and that quite some iodate is in solution already. When this point is reached, you can stop the electrolysis, but then you loose quite some unreacted iodide. So, you need to have a compromise between iodide lost and pulverization of the anode. This definitely happens, when a lot of oxygen is formed at the anode.

 

What happens is the following:

 

cathode: 2H2O + 2e ---> H2 + 2OH(-)

Anode: 2I(-) ---> I2 + 2e

 

By mixing:

 

I2 + 2OH(-) ---> IO(-) + I(-) + H2O

3IO(-) ---> IO3(-) + 2I(-)

 

The iodide formed is electrolysed again.

 

When I stopped electrolysis, I had a yellow solution. I added a very small amount of NaOH and then heated the solution. This assures that all hypoiodate and iodine is converted to iodate and on continued heating you also get rid of some water.

 

To this, I added a hot concentrated solution of KCl. On cooling down this gives crystals of KIO3. KIO3 is only sparingly soluble in cold water.

 

So, the method of making KBrO3 can also be used for making KIO3.

 

KIO3 is not very energetic from the point of view of pyrotechnics, it is totally different from KBrO3 in this. KIO3, however, can be used for many other nice experiments and this electrolysis experiment can easily yield you several grams of KIO3 from a few grams of sodium iodide.

 

-----------------------------------------------------

 

Now I have a question about the electrolysis with graphite. What causes the pulverization of the anode? I get this pulverization, as soon as oxygen is formed. Is this due to the bubbling? But if this is the case, then why don't I have this kind of problems with the cathode? All the time I had a lot of bubbling at the cathode and that is not pulverized at all.

 

I have observed the pulverization of graphite anodes very often in all kinds of electrolysis processes, and this always has wondered me. Has anyone an idea?

[YT2095]

Interesting!

 

try and make some Silver Iodide/iodate too, you could try that for photo sensitivity also.

 

as for the Anode, I`ve noticed this also, it`s almost as if it`s trying to make Carbon Iodate or Chlorate (which it can`t), there must be something to do with the electrical force ripping it appart molecule by molecule making it want to re-grow on the Cathode (which it can`t).

 

in an Ideal electrolyte (a carbon ion carrier that was conductive) that would be the reaction I`de expect to see though, the anode "vanish" and the Cathode increase in mass.

 

it would be interesting to find out what would happen if the carbon electrode was one Solid peice and not this Fused/bonded material that we use?

[raivo]

I too know these problems with anode. I think this is mostly due of low quality of carbon electrodes we use. Graphite from pencils will be pulverized very soon, that from batteryes is better but not much.

 

Destruction of electrodes depends also of current densitiy. Thats amount of electrical current flowing through electrolyser divided by surface area of electode. Professional electrolysers never use more than 0.5 A/cm2 but more often 0.07 ... 0.1 A/cm2. If we use graphite rod with diameter of 7mm thats soaked 5cm into electrolyte then working area is aproximately 10 cm2 so 1A of current will give current density 0.1 A/cm2. If you use graphite from pencils then acceptable current may be 100mA or even less.

[woelen]

[...']Professional electrolysers never use more than 0.5 A/cm2 but more often 0.07 ... 0.1 A/cm2. If we use graphite rod with diameter of 7mm thats soaked 5cm into electrolyte then working area is aproximately 10 cm2 so 1A of current will give current density 0.1 A/cm2. If you use graphite from pencils then acceptable current may be 100mA or even less.

Ah, that is interesting info... So, current density should not be too high. Your response gives me some interesting idea's. I'll start a new thread on electrolysis, here we go too far off-topic....

 

Any responses on electrolysis, please go to the new thread, which will appear within a few minutes. Here please continue on the KBrO3 and KIO3 and related things .