Boric Acid / Mg/Al conflict

[oldguy]

Please remember, a newbie here.

 

Plan is to make some extra long large sparklers for the grandchildren, with the comp below:

(of course, the children will only be allowed to use them under very close adult supervision)

 

Aluminum Al- 8%

Iron Filings Fe- 34%

Barium Nitrate Ba(NO₃)₂ - 45%

Boric Acid H₃BO₃ - 2%

Dextrin (C₆H₁₀O₅)_n - 11%

 

Excepting, I would like to include some Mg/Al.

 

Just did my 1^st few little chimney charcoal starter batchs of Mg/Al & it turned out great.

Shocked at how brittle it is.

 

Plan is to reduce the Fe filings to 24 & add 10 Mg/Al.

 

But, I gather Boric Acid & Mg/Al conflict.

 

Is there an easy inexpensive way to resolve that issue?

 

On another newbie note:

I have seen some sparkler comps that include some charcoal.

Is that for spark effect?

If so (?), can one use high quality ground lump mesquite charcoal for that spark effect purpose?

 

Thanks for any help here.....

 

　

 

Edited January 24, 2011 by oldguy

[Peret]

Is there an easy inexpensive way to resolve that issue?

Yes - leave out the boric acid. It doesn't come much less expensive than that.

 

The boric acid is there to make the comp very slightly acidic, because aluminum reacts with alkalies. Magnesium on the other hand reacts with acids, so boric acid does it no good and Mg compounds need a carbonate to buffer them. I've not heard that MgAl needs buffering with anything.

 

I think a larger proportion of MgAl will just serve to increase the burn temperature and will probably not make any sparks. The iron is there for the sparks. You probably should make a small batch first and see how it works out. Not sure about the charcoal, it may just be there to make the compound easier to light. Mesquite charcoal is said to be no good for black powder but probably makes excellent sparks.

[oldguy]

Thanks for the help.

But still puzzled?

 

Sparkler comp:

 

Aluminum Al- 8%

Iron Filings Fe- 34%

Barium Nitrate Ba(NO3)2 - 45%

Boric Acid H3BO3 - 2%

Dextrin (C6H10O5)n - 11%

"Boric acid is used primarily in some compositions containing aluminum to reduce sensitivity. "

http://www.diamondsparkler.com/

 

I thought the Boric Acid was included in the comp above to keep a reaction from happening with the Al. Dextrin is a water based binder used to make the comp into a slurry for dipping. Even fully dried, sparklers can eventually absorb moisture, if not perfectly stored. The object being that if they did absorb moisture, a reaction is possible with moisture & Al.

 

Am I missing something, because there is Al & a water based binder in the comp.

 

I read a thread somewhere Mg reacts with Boric Acid.

 

I assumed Mg/Al would have a similar reaction?

Edited January 24, 2011 by oldguy

[Bonny]

Thanks for the help.

But still puzzled?

 

Sparkler comp:

 

Aluminum Al- 8%

Iron Filings Fe- 34%

Barium Nitrate Ba(NO3)2 - 45%

Boric Acid H3BO3 - 2%

Dextrin (C6H10O5)n - 11%

"Boric acid is used primarily in some compositions containing aluminum to reduce sensitivity. "

http://www.diamondsparkler.com/

 

I thought the Boric Acid was included in the comp above to keep a reaction from happening with the Al. Dextrin is a water based binder used to make the comp into a slurry for dipping. Even fully dried, sparklers can eventually absorb moisture, if not perfectly stored. The object being that if they did absorb moisture, a reaction is possible with moisture & Al.

 

Am I missing something, because there is Al & a water based binder in the comp.

 

I read a thread somewhere Mg reacts with Boric Acid.

 

I assumed Mg/Al would have a similar reaction?

 

If using MgAl, I'd leave out the Boric acid.

If just making them with Al, leave the boric acid in. After drying, I wouldn't think moisture absorption would be an issue - think of all the stars made that (could) absorb moisture.

[ausgoty]

Without the boric acid there is a good chance an aluminium containing comp will react when the water is added.

 

I have had this happen and it is rather unsettling to feel the comp heating up as you mix it with a gloved hand. When this has happened I have just dumped it on a tray away from the work area and waited until the reaction stops. Its never gotten hot enough to ignite but they say it can. Can ruin the comp as the Al is half stuffed after a reaction like that.

 

Never had the problem with MgAl and water tho.

 

 

[Mumbles]

For what it's worth, I've never had a reaction happen without the presence of a basic salt like sodium bicarbonate or especially sodium oxalate while in the presence of flake aluminum. Furthermore, I've never had the reaction happen with barium nitrate, only potassium nitrate. Barium Hydroxide is poorly soluble and furthermore barium aluminate, the equivalent driving chemical which is formed as the aluminum oxide layer is removed, is just about completely insoluble, which would almost completely prevent any sort of reaction from getting out of control. The boric acid was probably added as a safety measure or to make someone feel better. It's likely not necessary. Given the thin coating on sparklers, I wouldn't be worried about spontaneous combustion. That only happens in fairly large batches where the mass can hold enough heat in to get to a sufficiently high temperature. Even 1 kilo batches are not nearly large enough, The thick slurry needed for sparklers would additionally help to prevent the mix from heating up enough.