10 replies to this topic

[defective]

can anyone tell me if calcium chloride can be used in pyrotechnics for red colouring to flames.

Or do people only use strontium for red flames.

i bought some CaCl2 in wilkos ( as a drying agent)

[spanner]

It's very hygroscopic, so its use would be limited. I have no comps that use it, of the hundreds that I have...

That being said, it might be worth a try, just to see how it goes. Might want to use a non-aqueous binder such as NC lacquer or red gum for binding.

I would expect more of an orange than a deep red, though.

Edited by spanner, 04 March 2009 - 02:12 PM.

[pyromaniac303]

I occasionally use it for force drying stars, by placing the stars in a sealed sectioned-off container, with the calcium chloride in one section and the stars in another. If left out, calcium chloride will turn to liquid within a few hours, it is used in a process for strengthening cardboard mortars posted on this forum.

Mortar Reinforcing

Or alternatively convert to calcium nitrate which is used in the kcnkickthecat colour system, however it is used in the orange and not the red formula.

[defective]

thanks guys,

[pyrotrev]

Or even convert it to calcium oxalate which isn't really hygroscopic at all and ought to give a better burning mixture than CaCO3.

[defective]

Or even convert it to calcium oxalate which isn't really hygroscopic at all and ought to give a better burning mixture than CaCO3.

any info on how this is done, im guessing reacting with oxalic acid, is seperation from the oxalic acid straight forward or a little tricky?

[EnigmaticBiker]

any info on how this is done, im guessing reacting with oxalic acid, is seperation from the oxalic acid straight forward or a little tricky?

Wikipedia suggests it should be easy, given its' low solubility in water (~0.0067 g/l) versus oxalic acid (~143 g/l) at room temps.

[Mumbles]

Yep, just mix the solutions, and it should come crashing out. Watch out, there will be HCl generated though. CaCO3 is used in several compositions as a orange agent. Similar method, but use sodium or potassium (bi)carbonate, and there is no HCl generated.

[a_bab]

Calcium chloride is so notoriously hygroscopical that your stars wil never dry. It's more potent that silicagel. Even if your stars are fully dried (in an exicator with more potent dessicants such as P2O5 or Mg(ClO4)2, even if binded with NC they will become moist in minutes.

HCl won't be produced out of CaCl2 and oxalic acid simply because HCl is a much stronger acid then oxalic acid. It's like saying that you can get sulphuric acid out of vinegar and copper sulphate for instance. It's simply not going to happen.

If you are after calcium oxalate (that would be formed as "kidney stones" in our kidneys IIRC) you need CaCO3 and oxalic acid (sold OTC as rust remover).

[Mumbles]

I was torn between if it'd work or not. On one hand there is the strength of acid argument. On the other there is the equilibrium pushing HCl gassing, and CaC2O4 precipitating. By the same argument NaClO4 and H2SO4 shouldn't be able to make perchloric acid, but it does via the precipitation of sodium sulfate. I've heard of it being done with HCl too, but am unsure how legitimate those claims are. Eh, I suppose the pKa values of these strong of acids are rather questionable and pretty similar so it may not matter.

Edited by Mumbles, 09 March 2009 - 03:38 AM.

[a_bab]

Perchloric acid is supposed to have a "strenght" close to nitric acid and sulfuric acid; still it's under these in termes of "strenght". That's why you can't get ammonium perchlorate out of ammonium sulfate/nitrate and perchloric acid.

Generally speaking, the reactions equilibrium can be "moved" in the opposite direction with some extra energy (usually heat); in the case of calcium chloride/oxalic acid the heat would ruin the oxalic acid anyway.