12 replies to this topic

[bigtonyicu]

***NO ONE TRY THIS PLEASE!!! Just thinking and wanting feedback; this could be very dangerous to test***

Hi Everyone,

I've been doing some digging with not much luck and am wondering is anyone has, or know where I can find, information on the following.

Some star compositions require the use of acid to control reaction between the chemical (Boric acid [I've even seen citric acid called for in some rare cases where boron would have undesired affects]). While it has some useful safety implications, in some rare cases it has some undesired side effect in the stars performance (during the desired reaction).

I've been digging in my old chemistry books and I can't seam to find any info on the reaction of molten anhydride acids with and anhydride bases (bicarbonate, hydroxide...) .

Most of these acids have a low melting point (150-200C).
Most of these Bases have a low melting point as well (50-400C)



This is where I�m going with this.



*** AGAIN� No one try any of this last thing you want is to get splashed by molten acids and/or bases (some strong bases are VERY powerful oxidizing agents [calcium hypochlorite] and not only will the burn you, the may catch any safety clothing on fire upon contact).


If a star could be safely made containing both of these, they should react first and destroy most if not all undesired side effect of the acid and or base.



I have access to a full lab but I�m very hesitant to set up a Bunsen burner in a fume hood with a test tube containing a mix of any of the above chemical with out any documentation, everyone else in the lab seam to be as concerned.



Does anyone have any information that I could use as a starting point?



Is there was a way of safely preventing the from reating during manufacturing and storing them,

[pyrotrev]

I guess you're wondering what will happen when the composition burns? My bet would be that there will be some reaction, but whether it will supress the side effects I'm not so sure. For instance if you have boric acid + a base, it'll form a borate, but the borate ion may still interfere just like the boric acid would have. Stopping them from reacting might be a pain too - you'll have to keep everything super dry!

[bigtonyicu]

I guess you're wondering what will happen when the composition burns? My bet would be that there will be some reaction, but whether it will supress the side effects I'm not so sure. For instance if you have boric acid + a base, it'll form a borate, but the borate ion may still interfere just like the boric acid would have. Stopping them from reacting might be a pain too - you'll have to keep everything super dry!

I'm trying to figure out if they will react at all with out a medium to exchange electrons in.

I agree that it would be a pain to create but bicarbonate are not soluble in Alcohol so it would be an easy base to work with win stars using alcohol soluble binder.

As for the creation of borates that’s not a huge problem they are VERY stable and shouldn’t react with a the stars affect.

A star containing both Potassium Bicarbonate and Boric Acid should create Potassium tetraborate (anhydride) it decomposes at well over 3000c and most flames won’t reach that threshold.

So back to the big question: Will “Potassium Bicarbonate” react with “Boric Acid” (both anhydride) by simply melting them together?

Edited by bigtonyicu, 24 November 2008 - 02:17 PM.

[digger]

I'm trying to figure out if they will react at all with out a medium to exchange electrons in.

I agree that it would be a pain to create but bicarbonate are not soluble in Alcohol so it would be an easy base to work with win stars using alcohol soluble binder.

As for the creation of borates that’s not a huge problem they are VERY stable and shouldn’t react with a the stars affect.

A star containing both Potassium Bicarbonate and Boric Acid should create Potassium tetraborate (anhydride) it decomposes at well over 3000c and most flames won’t reach that threshold.

So back to the big question: Will “Potassium Bicarbonate” react with “Boric Acid” (both anhydride) by simply melting them together?

I think the answer is yes they should react in the liquid phase as the ions are no longer imobilised. However it is the rate of reaction that is in question to make them usable and I suspect the rate of reaction is slow when compared to the burning rate of the star. So they will be destroyed (decomposed) before any significant quantities of the reagents can take part in this reaction.

Edited by digger, 24 November 2008 - 02:28 PM.

[bigtonyicu]

I think the answer is yes they should react in the liquid phase as the ions are no longer imobilised. However it is the rate of reaction that is in question to make them usable and I suspect the rate of reaction is slow when compared to the burning rate of the star. So it should not cause a problem as they will be destroyed before any significant quantities of the reagents can take part in this reaction.

I was expecting a fairly fast reaction with a fair amount of heat. for all intent is and acid base neutralization; with no water to absorb heat the temperature should climb fairly quickly once melting begins.

I'll stay at work late tonight and try a few tests with Sodium Bicarbonate, Potassium Bicarbonate, Boric Acid, Citric acid and a few stronger bases, if you'd like me to try out any particular mixes don't be shy I have most acids and bases to my disposal (Just don't ask me to try Perchloric acid with Potassium Hydroxide).

[digger]

I was expecting a fairly fast reaction with a fair amount of heat. for all intent is and acid base neutralization; with no water to absorb heat the temperature should climb fairly quickly once melting begins.

I'll stay at work late tonight and try a few tests with Sodium Bicarbonate, Potassium Bicarbonate, Boric Acid, Citric acid and a few stronger bases, if you'd like me to try out any particular mixes don't be shy I have most acids and bases to my disposal (Just don't ask me to try Perchloric acid with Potassium Hydroxide).

Yes I agree it should be a fast reaction (it will be interesting to see if it is pyrotechnic fast though), however in a star I would imagine the species only exist in a liquid state for a tiny fraction of a second as there is no time for significant heat transfer toward the core giving a very thin constantly decomposing liquid layer (anyone got access to a high speed camera?).

I suppose this makes it difficult to asses the results in a test tube as it will be difficult to get in the liquid as phase quickly. I assume that you will be pre mixing milligram quantities then melting them on a very thin flat plate from beneath to get them in a liquid state as fast as possible.

One thing to consider is that there may be no liquid phase when the star burns as the temperatures/heat at the surface could cause the components to miss the liquid phase and either sublime or decompose and react in the vapour phase.

Edited by digger, 24 November 2008 - 06:08 PM.

[bigtonyicu]

Yes I agree it should be a fast reaction (it will be interesting to see if it is pyrotechnic fast though), however in a star I would imagine the species only exist in a liquid state for a tiny fraction of a second as there is no time for significant heat transfer toward the core giving a very thin constantly decomposing liquid layer (anyone got access to a high speed camera?).

I suppose this makes it difficult to asses the results in a test tube as it will be difficult to get in the liquid as phase quickly. I assume that you will be pre mixing milligram quantities then melting them on a very thin flat plate from beneath to get them in a liquid state as fast as possible.

One thing to consider is that there may be no liquid phase when the star burns as the temperatures/heat at the surface cause the components to miss the liquid phase and either sublime or decompose and react in the vapour phase.

We have a 480 frame/second camera depending on the reaction might be fun to have a look

I plan on starting at 250 milligram of each on a on Pyrex plate over a Bunsen burner; but I might have to use a hot plate with and glycerin bath (bain marie) if I want any chance of seeing a molten phase. in a fume hood of course... not too worried about the by products but 100c+ acid and base not something I want to get splashed by.



(Not a huge fan of using an oil bath under something that could possibly ignite but the ignition temperature of the oil is much higher then that of the at acid base reaction should take place. The fume hood has a CO2 flood system so I can put out anything in a few second if the plate was to crack and somehow the oil ignited)

[pyrotrev]

Tip: use fairly coarse powders, that way the mixing will be limited to particle boundaries as the crystals melt and keep the reaction rate low. I doubt if it would be too nasty with a bicarbonate and a weak acid anyway.

Edited by pyrotrev, 24 November 2008 - 08:41 PM.

[bigtonyicu]

Tip: use fairly coarse powders, that way the mixing will be limited to particle boundaries as the crystals melt and keep the reaction rate low. I doubt if it would be too nasty with a bicarbonate and a weak acid anyway.

Bicarbonate is my starting point. Hydroxide might be next (potasium of course... I don't want sodiums low melting point.

[Mumbles]

What sort of stars do you think that boric acid is incompatable with?

If you're talking about stars containing sodium bicarbonate, it's a non-issue. I've never been able to get boric acid and bicarbonate to react in solution. There is no neutralization as boric acid isn't strong enough to protonate HCO3-. Only if stars were using sodium or potassium carbonate would anything really happen. I've successfully used boric acid solution in combination of sodium bicarbonate containing stars to prevent reactions that proceeded otherwise.

[pyrotrev]

Bicarbonate is my starting point. Hydroxide might be next (potasium of course... I don't want sodiums low melting point.

BTW, a lot of bicarbonates decompose to the carbonate + water and CO2 at quite low temperatures - worth checking the exact temp., so you know exactly what you're reacting.

[Alexander]

bigtonyicu,
This is a very confused question, you may as well ask how you can make ice cubes hot and cold at the same time so they freeze lemonade and boil coffie. The key is to stabilise the system at a single pH and you do this traditionally by including a quantity of the conjugate base. For example Acetic acid with Sodium Acetate in solution (Note, boric acid and borax is NOT such a mixture). If a small amount of strong base is added it will react with the acetic acid to form more acetate with little change in pH. If a small amount of strong acid is added it will react with the acetate producing more acetic acid, again with little change in Ph. The system is a stable equilibrium in both directions.

Normally you know which direction a pyrotechnic mixture is going to go so you only have to buffer in one direction, a sulphur-chlorate mixture (illegal in UK, just an example) is in danger of becoming too acid and can be made safer by a group II carbonate, a nitrate-aluminium mixture is in danger of becoming too basic and can be made safer by boric acid. The reasons these mixtures need stabilising and which direction they go should be obvious to anyone devising new ones.

Citric/boric acid and hydroxides/bicarbonates are not anhydrides (perhaps you meant anhydrous?), NaOH and KOH melt at very similar temperatures (around 318C and 360C). Acid base reactions do not require water. I'd suggest anyone publish any experimental mixtures before trying them even if they knew all this.

[digger]

Citric/boric acid and hydroxides/bicarbonates are not anhydrides (perhaps you meant anhydrous?), NaOH and KOH melt at very similar temperatures (around 318C and 360C). Acid base reactions do not require water. I'd suggest anyone publish any experimental mixtures before trying them even if they knew all this.

Interesting, I have always assumed that there either needs to be mobilisation of the ions either in a molten state, presence of water or some other polar solvent (no mater how small ) for these reactions to proceed. Therefore anhydrous solid acids and bases should not react I always thought.

Looking into a bit more, although I have not done an extensive search this paper seems to confirm my thoughts Click me. They describe that the solid phase reaction goes to completion when subjected to a RH of 80%, however if the RH is 11% no reaction occurs indicating the need for water to mobilise the ions.