2 replies to this topic

[YT2095]

this is really bugging me now!

I`ve tried Perchlorate and (metal)Benzoate mixtures and they all work quite nicely with AmPerc and KPerc.

Benzoic acid on it`s own doesn`t do anything, so I tried Ammonium Benzoate instead, that doesn`t work either!

so for Some reason it has to be a Metal Ion attatched to the Benzoic in order for the reaction to take place.

I`m at a complete loss as to Why this is the case, esp when you consider that AmBenz doesn`t work either.

Anyone?

[Mumbles]

I can assume you're talking about whistles, though you don't specifically mention it. I have heard a very weak whistle can be made from benzoic acid, but that is beside the point. Your problem here is a decomposition problem. Normally whistles burn in a vibratory manner, which causes the whistling. There is a bit of debate as to how the phenomenon happens, but it's said to be an oscillation in the tube hitting harmonics or something. I've heard something about CO2 from the benzoates blanketing the surface, and exploding a short period of time later, over and over similar to dragon eggs. Anyway, I think your problem is decomposition of the ammonium benzoate before it can be utilized by the perchlorate.

Many ammonium compounds will start decomposing at or very near it's melting point. Being a salt of an organic acid, this is even more likely. Ammonium Benzoate melts at 198C, while both the sodium and potassium salts are well over 300C. I couldn't find any exact data. I'd say it's an easy assumption that whistle mixes will burn above 200C. Perhaps the temperatures produced are decomposing the product before it can be combusted. It is likely to form benzoic acid and ammonia upon decomposition at this low of a temp, which you have already discovered makes a poor whistle fuel. Another possibility is the ammonia that is formed, and you know there is gaseous ammonia from this, is killing the vibratory burning in one way or another.

Just tossing out some ideas.

Edited by Mumbles, 05 September 2007 - 05:56 PM.

[YT2095]

That makes a lot of sense! yes it was whistle mix I was thinking off only this was just the loose powder in a small heap on a steel plate and not made into anything.
the Temperature differences seem to be the culprit, Thanks