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Author Topic: Help with writing a FLASH POWDER combustion rxn??  (Read 6087 times)

Offline bigggmike1

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Hi everyone,
I'm doing a project in school on various types of combustion, and I thought burning some flash powder in front of my class would create a nice, spectacular demonstration.
Of course, if I'm going to present such a thing, I need to know more about it.

Flash powder is a mixture of Aluminum powder, potassium perchlorate, and a little bit of sulfur.

I've been trying to figure out what this combustion reaction would look like on paper, but I'm at a loss.  I would like to put the reaction up on the board before I combust the powder, and I would like to explain some things about the reaction.
I do know that potassium perchlorate is the oxidizing agent in the reaction.

I would greatly appreciate your help in writing this chemical reaction.  Thank you.


 

Offline bigggmike1

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Re: Help with writing a FLASH POWDER combustion rxn??
« Reply #1 on: 19/05/2006 03:28:20 »
Hey guys, presentation is coming up at the end of next week and, honestly, you people are one of my last efforts to get this information.

I know there are some chemists/past chem majors out there!!!  

If you need any clarification on the rxn, just ask.

Thanks for any help
 

Offline rosy

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Re: Help with writing a FLASH POWDER combustion rxn??
« Reply #2 on: 19/05/2006 12:20:35 »
Well, potassium perchlorate is an oxidiser, so you'll be making KCl and (I'd guess) Al2O3. This is a guess:
K+ ClO3- + 2Al --> Al2O3 + K+ Cl-
I would guess that the sulphur reacts first, oxidised to SO2 and/or SO3, and will release enough heat that the main reaction with the aluminium powder can start.
 

Offline Mr Andrew

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Re: Help with writing a FLASH POWDER combustion rxn??
« Reply #3 on: 27/05/2006 18:35:13 »
Actually, potassium perchlorate is KClO4.

The revised equation should look something like:
3K+ + 3ClO4- + 4Al --> 4Al2O3 + 3K+ + 3Cl-

You should add a little more KClO4 so it can react with the sulfur but be careful as perchlorates are extremely shock sensitive!!!![xx(]

Another good demonstration is sugar and potassium chlorate (KClO3).
-Put some KClO3 in a test tube and heat it up until it melts.
-Then drop a jolly rancher down the tube and stand back!!!:D
-Produces a brilliant flash of light and sometimes rockets the candy across the room (be sure to aim away from the audience and use a blast shield)
-There is also a risk that the test tube could shatter! (That happened in my class when my teach was demonstrating reaction rates)[B)]

Good Luck in your presentation!

"His mind is the ultimate weapon!"-MacGyver television series
 

Offline Nick Meyer

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Re: Help with writing a FLASH POWDER combustion rxn??
« Reply #4 on: 05/06/2006 04:07:19 »
I will not be much help as far as the formulas go but I have never heard of flash powder with sulfur. just use german dark aluminum powder and potassium perchlorate in 30/70 proportions aluminum/perchlorate by weight. This stuff is a great explosive under pressure (AKA M-80's, chery bombs, and silver salutes).

Nick
 

Offline Mr Andrew

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Re: Help with writing a FLASH POWDER combustion rxn??
« Reply #5 on: 06/06/2006 23:01:38 »
The sulfur in the flash powder burns very easily and adds heat to the reaction so as to speed it up.  It also burns blue and releases a wonderful smell!![xx(]  That is why they use it in black powder.

"His mind is the ultimate weapon!"-MacGyver television series
 

Offline lightarrow

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Re: Help with writing a FLASH POWDER combustion rxn??
« Reply #6 on: 09/08/2006 19:41:38 »
Sulfur, in black powder and in flash powder, is used for many reasons. Some of them are:
to catalize the reaction; to increase flame, friction and shock sensitivity, to make the powder less hygroscopic, to make the combustion more homogeneuos. So the speed of reaction increases, the ignition temperature decreases. The heat released is not higher, however, but lower.
 

Offline lightarrow

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Re: Help with writing a FLASH POWDER combustion rxn??
« Reply #7 on: 15/08/2006 11:43:10 »
By the way, even if it should have been quite clear from what I have said, sulfur is not necessary at all, as nick suggested. If the powders are very fine, dry and well mixed (in the right proportions, of course) and you don't want or need to increase powder's sensitivity, the reaction is even hotter and powerful without sulfur.

Remember not to use KClO3, but KClO4, instead, if you can. Al/KClO3 (and, even more true, Al/KClO3/S) is very dangerous: high sensitivity (as I said, even shock sensitivity) and instability = it could even explode without any reason, in some conditions, for example in presence of moist (when there is moist in the air? Always!).
« Last Edit: 15/08/2006 11:54:32 by lightarrow »
 

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Re: Help with writing a FLASH POWDER combustion rxn??
« Reply #7 on: 15/08/2006 11:43:10 »

 

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