chlorine donors?

[stormyweathers]

i read on pyroguide about chlorine donors, and how they can enhance color. But it also mentioned how if KClO4 or any nitrate is used as an oxidizer, supplemental chlorine is necessary. why exactly is this?

[Ralph]

chlorine donors are chemicals (with chlorine in them) which when they burn can have their chlorine "taken" by another chemical. the reason we want compounds like this is becuse the chlorides of colour producing chemicals produce the best colour. and example of this is you can get a pink type colour with strontium carbonate (or nitrate) with out any chlorine donor but it wont be very rich as soon as you add a chlorine donor it will become red. some colours like green require a chlorine donor as with out one barium gives a brilliant white. and a chlorine donor is also used to change the oxidation state of the compounds (copper(ii) gives a green flame but copper (i) gives the blue we are after) the most commonly used chlorine donors used today are parlon saran and pvc

[stormyweathers]

ok, thanks. do you know WHY the chlorides produce better colors?

and just to make sure that im getting this: we cant just add the chloride salts directly because they are too hygroscopic, correct?

[Yankie]

ok, thanks. do you know WHY the chlorides produce better colors?

and just to make sure that im getting this: we cant just add the chloride salts directly because they are too hygroscopic, correct?

From what I have heard colour is produced when monochlorides are burned, such as copper/barium/strontium monochloride for blue/green/red ect. Monochlorides are produced when a metal salt and chlorine donor react together when the composition is burned.

When you say the chloride salts do you mean copper/barium/strontium chloride?

[Mumbles]

The chloride salts that are stable at room temperature, arn't the same color emitters that are present in flames. It's probably better to call them "chloride species". BaCl, SrCl, and CuCl are the species present in flames. BaCl2, SrCl2, CuCl2, and Cu2Cl2 are the ones that are stable (relatively) at room temperature. But yes, you're right that they are usually too hygroscopic, expensive, or for whatever reason unsuitable for normal use. It should be stated that you can probably make good stars from them, but they're just not all that useful for normal use.

 

Chlorine has an additional use in that in produces Aluminum and magnesium chlorides. These work in the opposite way in that they produce no, or little color. Al2O3 and MgO are the salts that will form without chlorine around. These are blackbody emitters, in that they produce across many wavelengths, thus producing white light, and washing out colors.

 

These two uses combined will give the best colors possible. An excess of chlorine is often used to ensure high conversion.

 

Perchlorate, unlike chlorate, just doesn't give up it's chlorine when burned. Thermodynamics are probably to blame. I've heard that adding sulfur can help it to give up some chlorine. This is why old chlorate formulas often contained sulfur, despite the danger. Paris green also caused it to give it up I do believe. Potassium Nitrate doesn't have any chlorine, so there is none to give.

 

Below is a wavelength list of common emitters from Hardt. A wavelength to color guide should be easy to find if you don't know them off hand. Ah, if only fluorine emitters were more available and better behaved. The BaOH, etc emitters are the ones formed without the chlorine present.

 

http://www.apcforum.net/Mumbles/Hardt.jpg

[TYRONEEZEKIEL]

Why do you want the fluoride mumbles?

[stormyweathers]

thanks for that informative post mumbles.

 

but WHY is it that chloride species have richer colors?

does it have to do with the ionic radius, electron affinity, or what?

 

 

 

[and would PTFE be a fluorine donor?]

[Bonny]

[and would PTFE be a fluorine donor?]

 

 

I don't think so, as there is no chlorine to donate.

[stormyweathers]

hence the words "Fluorine Donor"

[Bonny]

hence the words "Fluorine Donor"

Missed that one... I was probably assuming chlorine as I have yet to hear of flourine being used in pyro.

[Mumbles]

In the above list, many of the fluorine species correspond to very pure colors. I don't think teflon would work, though I've never tried it. The temperatures required to get it to give up it's fluorine, would probably wash out any color imaginable. Then again I've heard of people generating poisonous fumes (reportedly) on stovetops with teflon coated pans.

[Bonny]

In the above list, many of the fluorine species correspond to very pure colors. I don't think teflon would work, though I've never tried it. The temperatures required to get it to give up it's fluorine, would probably wash out any color imaginable. Then again I've heard of people generating poisonous fumes (reportedly) on stovetops with teflon coated pans.

 

 

Are any flourine species commonly used? Or not due maybe to cost or difficulties in obtaining??

[TYRONEEZEKIEL]

So fluorine salts may give the best colors?

[stormyweathers]

can anybody help explain why there seems to be a correlation between electronegativity and color purity?

 

or is the correlation ionic radius?

in which case hydrides would produce even purer colors.

Edited July 8, 2009 by stormyweathers

[Swede]

When atoms, molecules, and ionic species are energized by any number of means (heat, uWave radiation, etc) they have characteristic spectra which result from the excited electrons transitioning from a higher to a lower energy state. When the electrons make the jump, they emit photons of light at a very specific frequency. This is how astronomers can determine what is in an atmosphere from vast distances - they look at the spectrum emitted, and this spectrum will have very distinct peaks which correspond to an exact atom, molecule, or ion. There are slight variations, it's more of a bell curve than a line, due to doppler and lifetime broadenings, but they are distinct enough for a scientist to say "Titan as a lot of methane in its atmosphere" for example, long before any probe ever actually sampled it.

 

I can't get more specific than that, because I have forgotten most of it, but the purity of color the human eye perceives can be improved by focusing on a specific transition. When a star burns, if we can create a situation where 95% of the light is emitted at 510 nm, we will see a brilliant green, but if only 75% of the light is at 510 nm, and there is a hash of other wavelengths, then the perceived color will be washed out, altered, or less than vivid.

 

Note the wavelengths of the Barium compounds in Mumbles' table - very close to 510 nm, green.

[Mumbles]

In theory fluorine compounds would make some very nice colors, but I don't think anyone has ever really tried, or was successful. Fluorine is just too hard to deal with, and generate, not to mention the toxicity. It's rather difficult to generate pure fluorine gas, as it is going to react violently with whatever is closest. It's not worth the effort. Bromine donors on the other hand have potential, but are quite expensive.

 

I'll get back to you on the ionic radius and electronegativity thing. I have some things to look up.

[stormyweathers]

maybe ionic radius is more relavent because if the electrons are closer to the nucleus, they would be held in stronger. Making then harder to excite, and thus reducing the photons emitted. This would allow the energy from the fire to excite the cation's electrons more efficiently. This could account for the purer colors.

 

has anybody used hydride salts?

this piece of info could confirm my hypothesis.

[TYRONEEZEKIEL]

Why do halogens give the desired brightening and coloring effect?

 

I know halogens are used extensively in light bulbs for the same reason

[Mumbles]

You know, they're called halogen lights, but I think they usually contain noble gases like Xenon.

 

The halogen species are just better emitters. Short of sodium, and maybe calcium, the emitting species in flame are not atomic species, they are always molecules. If it's not a halogen complex, it'd be a good bet that it's an oxide or hydroxide, which just don't give as nice of colors, or tend to give a broad spectrum. It could be because the bond is stronger, higher electronegativity, that the various electronic transitions are closer in energy, so thus a large number of transitions close in energy giving off a broad band. The appropriate transitions may also be too high in energy to give off anything clean.

[Swede]

The trick with pyrotechnic comps and chlorine donors is that the act of burning creates short-lived species that cannot exist, or are unstable, at room temp. We're looking at decades if not hundreds of years of trial and error to make the famous, known comps give off the light that they do. If it were only as easy as burning a pile of BaOH, we'd get a pure green that would be glorious. Of course Barium Hydroxide exists as Ba(OH)2 and it is a hydrate. So we create comps that, in burning, maximize the creation of species that emit the desired wavelength while minimizing other undesirable wavelengths. The use of the chlorates and perchlorates opened pyrotechnics up for superior colors, as did the use of metal flake, which gives higher temps and can create species (with their associated light wavelengths) at an intensity that is otherwise impossible.

 

I think one of the reasons blue is so tricky is because it is a shorter wavelength, requires more energy to create and emit, and the act of pumping up a comp with a lot of energy to make blue also tends to create other, less desirable species at longer wavelenths that overwhelm the blue.

 

In the military, there are (I believe) comps that emit gobs of IR light invisible to us but very visible to IR vision devices. Compositions can be readily tailored to a given frequency, but it is never perfect. It's an interesting study overall.

[stormyweathers]

@mumbles

if the electronegativity on the chloride ion would cause bands like that, this would only account for a single color to be produces by chloride salts.

 

i would imagine that the electronegativity wouldnt allow for the electrons to become excited, forcing the cation's electrons to become excited instead.

 

i know im not phrasing this correctly, but is it comprehensible?

[Mumbles]

I understand what you're saying, but I really don't have a true explaination as to why they are better. It's definitely mainly a function of the metal as the chloride only enhances a natural color. I'd have to look up some transitions, and try to get some ideas from there. I've come up with a lot of ideas over the last few days contemplating it, but who knows if any of them actually have any merit.

[stormyweathers]

i appreciate the thought your putting into it

 

do you mind sharing all of your ideas?

just so i can think more in depth about it too.