Boric Acid - Archive File

[megalomania]

CragHack
Frequent Poster
Posts: 618
From:
Registered: DEC 2000
posted 05-10-2001 12:16 AM
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I am considering making some salutes for the 4th using a flash composition of either:
KMNO4, S, and Al

or

NaNO3 S, and Al.

Now i know they are both fairly unstable and was wondering if the addition of boric acid into the mixes would be a good way to desensitize them. but not enough so as to be impervious to a fuse. i was thinking about 1% boric acid by weight. Any thoughts?

oh, also, if boric acid can be used, can someone tell me why it will act as a desensitizer? thanks.

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"If you must, do it with intelligent people, at least they know how to talk to the cops."



Anthony
Moderator
Posts: 2306
From: England
Registered: SEP 2000
posted 05-10-2001 01:48 PM
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The second comp you've listed should be pretty stable, especially with some boric acid. I believe boric acid is used to prevent metals in the comp reacting (e.g metal + nitrate). So it doesn't desensitse the comp but prevents spontaneuos ignition.
I'm sure one of the pyro mad guys here could explain in more detail.



the freshmaker
Frequent Poster
Posts: 175
From: Heaven
Registered: DEC 2000
posted 05-10-2001 02:09 PM
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When you are using nitrates in flashpowder the nitrate could react with the Aluminium causing heat which could ignite the flashpowder. The boric acid prevents that reacting to start.
I don't think boric acid would make KMnO4 flash any safer.
If I was going to make some (powerfull) salutes I would use the KMnO4-flash rather than NaNO3 flash, but the KMnO4 flash is more sensitive.

The dangerous reaction between the NaNO3/KMnO4 and Al. first start after some hours or days so there shouldn't be any problem if you are using the salutes right after production. But be VERY carefull anyway!


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good boy with bad ideas



CragHack
Frequent Poster
Posts: 618
From:
Registered: DEC 2000
posted 05-10-2001 04:51 PM
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oh i do not plan on storing anything longer than 24 hours. But i like to play it safe anyway. Thanks for the info gentlemen.
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"If you must, do it with intelligent people, at least they know how to talk to the cops."



blackadder
Frequent Poster
Posts: 313
From: London
Registered: DEC 2000
posted 05-10-2001 05:28 PM
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If you want to sensitize some NH4NO3 (Ammonium nitrate) with some Al, there is a hazard of the Al reacting with the NH4NO3 and there is a possibility of accidental ignition/detonation.
With the addition of 1% boric acid, this risk can be eliminated.



-A-
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Posts: 100
From:
Registered: JAN 2001
posted 05-15-2001 12:32 AM
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Can stearic acid be used for the same purpose?


PHILOU Zrealone
Frequent Poster
Posts: 479
From: Brussels,Belgium,Europe
Registered: SEP 2000
posted 05-15-2001 08:01 AM
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It is used to improve water/moisture resistance nothing to do with reactivity with Al powder (wel not directly because the reaction is favorised by water!).

[GibboNet]

I always thought that Ammonium Nitrate could only react with the Aluminium if it was wet, or at least enough moisture for some AN in solution around the Al.

So if your AN is perfectly dry, there should be no problems right ? (i'm not thinking of using it in LE's, only AN Explosives. )

Does Boric Acid de-sensitise most chlorate / nitrate mixes, or is this particular? And is the way it works by forming a water proof barrier between the reactants, or does it absorb the water first?

Also, does anyone have a source of boric acid, especially in Australia.

[iron raven]

hello,
talking about NaNO3/s/al flash, would KNO3/s/al flash work? i have tryed and had abosoulety no success with this mixture. i used KNO3 70 parts to 20 parts sulphur to 10 parts Al. this stuff wouldn't even ignite. I got an ignition after i added sugar to the mix. so can one tell if my mixture won't work becouse of the absense of sodium nitrate? if my mix does work can one tell me how or why it didn't ignite? any info would be of great help thank you.
iron raven

[Mr Cool]

There's a white flare mixture that I have used that was similar in composition to that, except the ratios of Al and S were different. So it was something like 70:20:10, KNO3:Al:S. Maybe not exaclty, but it was roughly that.
"Paint-grade" Al was used, and it was a bitch to ignite. I used thermit to do so, although I'm sure plaster incendiary grains would do it. I had not heard about that stuff when I was messing with it.
An even when lit, I doubt it could function as a flash powder. It burned bright, but SLOW.

[arm]

To get nitrate flashes to work you need really really fine aluminium and nitrate, some people claim to have made this work with course aluminium but i think this is BS.

Various mixes to try are

6:3:1......................KNO3:Al:S (Bangor Powder #1)
4:1:1......................KNO3:Al:S (Bangor Powder #2)
7:5:1......................KNO3:Al:S
5:4:1......................KNO3:Al:S (Arm #1)
5:3:1......................KNO3:Al:S (Arm #2)
5:2:3......................KNO3:Al:S (Allen)
5:3:2......................KNO3:Al:S (Allen Modified)

The best i've got with filler grade Al (200-325) mesh was blowing out the fuse hole in a shower of sparks with a quiet bang.

GibboNet:

Dont mix Boric Acid with chlorate and aluminium otherwise you'll be scraping your fingers off the ceiling.

[inFinie]

Why H3BO3 works as desensitizer?
If it reacts w/metal then composition ratios will change or what?

[arm]

Boric Acid doesnt really act as a desensitizer in Nitrate/Aluminium Compositions, instead it prevents possible spontanious decomposition.

If the mix becomes damp the aluminium starts to reduce the nitrate to amide. This reaction generates heat and can ignite the mix.

This reaction doesnt take place in acidic conditions so it is advisable to add 1-2% of boric acid to the total weight of the comp.

[Mr-Eckted]

Would one be correct in assuming that if you added a strong base to the mix ( a small amount ) that it would make it more likely to ignite when exposed to water?

[vulture]

Do NOT add boric acid to permanganate flash!!! Acidic environment makes KMnO4 flash VERY unstable!

[arm]

Permanaganate flashes are made more dodgy because of the autocatalytic nature of KMnO4.

Is there a way to desensitize KMnO4 flash by adding something to slow or prevent the formation of MnO2?

[GibboNet]

Thanks arm, no, I was only interested in it's use in AN HE's.

Just out if interest, have you got an equation that shows how AN may decompose to amides with Al ?

Would other acids be suitable ? I assume that boric acid is named becauseit is useful in a certain aspect.

[inFinie]

I mean why that reaction will not take place if boric acid is added.

[arm]

One reaction is as such i believe:

8Al + 3NH4NO3 + 18 H2O -> 8Al(OH)3 + 3NH4OH + 3NH3 + heat

So the reaction evolves ammonia - a good sign that something bad is happening.

Any acid is usable as long as it isnt hydroscopic.

[scarletmanuka]

Iron Raven, your KNO3 flash will work, what did you ignite it with. KNO3 flash mixtures are very insensitive to heat and the S + KNO3 reaction would not be hot enough to ignite the Al + KNO3 reation. The best idea would be to reduce the amount of sulfur and increase the amount of Al,
ie 60%KNO3 30%Al 10%S and try to ignite it with a sparkler, you should have no problems.

[inFinie]

Reaction should be
8Al + 3NH4NO3 + 15 H2O -> 8Al(OH)3 + 6NH3 + heat
Cause of heat NH4OH -> NH3 + H2O (this happens @ room temperature too, indeed.)
Is Al(NO3)3 stable? (comparing with KNO3)