7 replies to this topic

[sasman]

Hi
I have just tried making some Round Stars using the Dixon Flitter Formula.. It contains Lots of Flake Al ranging from -20 to -326 mesh .The oxidizer is KNO3..Know there is no mention of Boric acid in the Formula? Should have i addded some?

...So i useed 25% alcohol/water and dextrin as the Binder...Now i have been drying them since yesterday and im getting a nasty whiff of Hydrogen sulphide?...

The stars are not getting warm, just a nasty whiff..I have read/heard about the Nitate Al reaction But they usualy mention a smell of Ammonia and Heating of the Comp?... Is this normal Reaction for Dixon Flitter?..

[RegimentalPyro]

Safety Tip!: Get them outside and away from all other comps ASAP. Ensure they are located such that if they do ignite, they will not do any harm. [You probably have already done this?]

I am unsure of this but my gut instinct is that Boric acid should have been included in the comp. Someone more chemically aware than I am should be able to tell you for sure......

[Richard H]

Always add boric acid to compositions containing aluminium and nitrates. It would be best to add the boric acid to the solvent, and then dampen the composition with it.

[paul]

As you stated it smells like H2S. So it is not the reaction between KNO3 and Al but between the Al and S.
If the amount of Al is very high and Sulphur is added a reaction takes place and Al2S3 builds up. This reacts with water to generate H2S.

There?s no real way to prevent this, just dry them faster or coat your aluminium!

[Lefty's Mixing Shed]

The characteristic smell of hydrogen sulfide (i.e., H2S) can be detected at remarkably low levels (i.e., parts per billion in air). If the smell is slightly offensive and it doesn't get worse with time, you're normally okay. If the smell is downright overpowering or seems to be getting stronger over time, it's probably best to dispose of the offensive material. Fireworks compositions aren't supposed to evolve large amounts of H2S. If yours does, there is something wrong.

A word of caution: Your ability to smell H2S is compromised as you smell H2S. The best way to know whether the smell is getting stronger or weaker is the leave the area for a few mins and re-enter.

[Rhodri]

Very good advice there Lefty!

[sasman]

The smell has finally stopped ..They didnt get warm ...I hope that the reaction has not destroyed the`stars ill give it a day or so more before i try a burning a few...i have tried to ignite them but they wont ignite even from a blow torch..

I rolled the stars with homemade Al Flitter with no Coating so it appears to be true about uncoated Al is more reactive..So next Time ill add boric acid to the Solvent..I would like to have know what chemical reaction were to create Hydrogen Sulfide?

[paul]

As I stated in an earlier post I think the following occured:

- Al and S reacted to Al2S3 (This happens even if you only mix these two chemicals together without KNO3 or any other oxidizer...)

- This Al2S3 then releases H2S if it comes in contact with water or only the humidity from the air. (It does?nt need much water for that...)

I think that?s it. Please feel free to comment/correct it

Edited by paul, 18 October 2004 - 07:00 AM.