making potassium (per) chlorate

[WSM]

I've acquired a second platinized titanium anode, designed for jewelry plating. I'm not sure if the coating is thick or hardy enough to handle the riggors of a perchlorate cell, but we'll find out !!!

 

WSM

Edited July 21, 2014 by WSM

[pyroChile]

 

Hi pyroChile,

 

This statement is not true as written. Swede succeeded in converting potassium chlorate to potassium perchlorate with a platinized titanium anode, and detailed the process in his blog.

 

To say it's not practical may be more accurate.

 

The notion of it being impossible is common, and even Dr. Shimizu states it in his book, Fireworks, the Art, Science and Technique.

 

WSM

 

 

Hello WSM!

 

 

It's true, is not practical, since large volume of electrolyte is required. Furthermore the much lower concentration of chlorate, which would facilitate the anode erosion.

 

 

Best,

 

 

=)

[taiwanluthiers]

But the problem is, how do I purify sodium chlorate since it has higher solubility compared to sodium chloride? I ran one sodium chlorate cell forever and ever (like more than a week) without anything at all, so I guess I would have to boil the large volume of electrolyte into half of its volume before I'll see anything?

 

Purifying potassium chlorate is easy and I already made a huge amount of it, but now I don't know what to do with them...

[WSM]

I found a useful table from an article on perchlorate manufacture (the source is Kirk-Othmer, I believe. Edition unkown):

 

Table 1 Sodium Perchlorate Cell Operating Information

Current, A 500-5000

current density, kA/m² 1.5-5.2

cell potential, V 4.8-6.8

anode PbO₂ graphite, platinum, or Pt on copper

cathode bronze, stainless steel (316), or iron

anode-cathode spacing, cm 0.2-3

current efficiency, % 90-97, Pt and 85, PbO₂

temperature, ^oC 30-60

pH 6-10

sodium dichromate concentration, g/L 0-5

electrolyte concentration, g/L

initial

NaClO₃ 100-700

NaClO₄ 0-700

end

NaClO₃ 3-100

NaClO₄ 500-1100

energy consumption, kWh/kg of NaClO₄ 2.45-3.0

platinum consumption, g/t of NaClO₄ 2-7

operation mode batch or continuous

 

I determined the current density in A/cm² to be 0.15-0.52,

a workable cell potential of 5.0 to 6.0 Vdc,

a decent electrode spacing of 0.5" (~12mm),

and an initial sodium chlorate concentration of 500 g/L.

 

We'll see if these numbers work in practice...

 

WSM

Edited July 22, 2014 by WSM

[taiwanluthiers]

Problem with potassium chlorate as a starting chemical I ran into is, the best I can do is about 200 grams per liter, and that's if the cell liquor temperature is maintained at at least 50C. When I ran the cell at 5 volts it drew maybe 3-5 amps, and the cell temperature just wouldn't stay up at all, causing crystals to form (chlorate crystals).

 

Sounds like I am back to square one... I guess I could possibly run a chlorate cell and get a healthy crop of sodium chlorate (which could probably take a while) and then I guess I could use the potassium chlorate as a feed stock to react with sodium perchlorate.

[WSM]

Problem with potassium chlorate as a starting chemical I ran into is, the best I can do is about 200 grams per liter, and that's if the cell liquor temperature is maintained at at least 50C. When I ran the cell at 5 volts it drew maybe 3-5 amps, and the cell temperature just wouldn't stay up at all, causing crystals to form (chlorate crystals).

Sounds like I am back to square one... I guess I could possibly run a chlorate cell and get a healthy crop of sodium chlorate (which could probably take a while) and then I guess I could use the potassium chlorate as a feed stock to react with sodium perchlorate.

 

I would use KCl solution instead of KClO₃ solution to exchange with NaClO₄. The KClO₄ would drop out immediately and the resulting NaCl solution could start over in the NaCl to NaClO₃ system.

 

The potassium perchlorate can be separated in a Buchner funnel and washed with chilled, pure water before drying and storage. The wash water can be used for replacement water in the chlorate making part (so there's practically no need to waste much of anything).

 

WSM

Edited July 21, 2014 by WSM

[taiwanluthiers]

So basically the huge amount of potassium chlorate I have is useless? I thought I could react it with sodium perchlorate, and then the leftover solution could be fed back into the perchlorate cell...

[WSM]

So basically the huge amount of potassium chlorate I have is useless? I thought I could react it with sodium perchlorate, and then the leftover solution could be fed back into the perchlorate cell...

 

That's a nice thought (about using the potassium chlorate to exchange with the sodium perchlorate), but I don't know if, or how well, it would work in practice. If you try it, let us know how it works for you (and the particulars of your approach to it).

 

As for the potassium chlorate being useless?! Maybe for feedstock, unless you have solid platinum anodes. But for other things, it's very useful; in H-3 coated rice hulls for small shell burst, for color stars with excellent colors and LARGE flame envelopes, for color smoke compositions, and the list goes on and on...

 

Don't give up on potassium chlorate. It definately has it's place in fireworks, and when used with judgement and skill, it's not the boogeyman that so many folks say it is. If you know, understand and respect it's characteristics, it can be your very good friend!

 

WSM

Edited July 22, 2014 by WSM

[taiwanluthiers]

Well the theory being that potassium perchlorate having very little solubility so if I say try to dissolve some potassium chlorate crystals into a solution of sodium perchlorate, potassium perchlorate crystalizes out while more potassium chlorate gets dissolved and reacted with the sodium perchlorate solution until the crystals are gone. Then you are left with potassium perchlorate and a solution of sodium chlorate that could then be used in a perchlorate cell to make more sodium perchlorate...

[MrB]

Problem with potassium chlorate as a starting chemical I ran into is, the best I can do is about 200 grams per liter, and that's if the cell liquor temperature is maintained at at least 50C. When I ran the cell at 5 volts it drew maybe 3-5 amps, and the cell temperature just wouldn't stay up at all, causing crystals to form (chlorate crystals).

Well, not having it staying above 50c cant really be a major production issue. Insulate the bucket. Going to be a small hell getting it "just right" but since your constantly putting energy in to it, it's just a matter of finding the right balance. Somehow i think it's best to start out with "to much" insulation, and monitor it right from the start, and remove a little as you see the temp climbs to high, and watch for the result, still climbing, remove some more. Sticks of styrofoam around the bucket and removing them on one side should help the bucket crate some convection powered circulation to.

 

At the end of the process the wattage going in to the bucket drops of, i believe? Would probably been more self regulating if it went the other way and increased the temp, since that would increase the salt levels again, and keep the cell going for longer... Not really my field. Just wanted to pipe in and say "don't give up over not being able to get the temp UP, going in that direction is always both easy, and cheap."

 

Good luck.

B!

[WSM]

Well the theory being that potassium perchlorate having very little solubility so if I say try to dissolve some potassium chlorate crystals into a solution of sodium perchlorate, potassium perchlorate crystalizes out while more potassium chlorate gets dissolved and reacted with the sodium perchlorate solution until the crystals are gone. Then you are left with potassium perchlorate and a solution of sodium chlorate that could then be used in a perchlorate cell to make more sodium perchlorate...

 

I suppose I'd use a saturated potassium chlorate solution to add to the sodium perchlorate solution, filter and wash the potassium perchlorate precipitate, and use the rest of the liquid in the next run (if all that makes sense). For my attemps, I'll use KCl instead of KClO₃ to make the potassium perchlorate.

 

If you try the system the way you describe, I'm very interested to see how it works out. Please share your results with us.

 

WSM

Edited July 22, 2014 by WSM

[WSM]

Well the theory being that potassium perchlorate having very little solubility so if I say try to dissolve some potassium chlorate crystals into a solution of sodium perchlorate, potassium perchlorate crystalizes out while more potassium chlorate gets dissolved and reacted with the sodium perchlorate solution until the crystals are gone. Then you are left with potassium perchlorate and a solution of sodium chlorate that could then be used in a perchlorate cell to make more sodium perchlorate...

 

After sleeping on it, I think the likely results of using potassium chlorate to exchange with sodium perchlorate, is that the potassium chlorate won't all be reacted and your potassium perchlorate will have high levels of potassium chlorate contamination.

 

I think because potassium chloride is so much more soluble than potassium chlorate, that the chloride should be the first choice in turning sodium perchlorate to potassium perchlorate. It would result in the purest end product.

 

KCl(aq) + NaClO₄(aq) > KClO₄(solid) + NaCl(aq) at STP

 

That's my two cents.

 

WSM

Edited July 22, 2014 by WSM

[taiwanluthiers]

What about heating the solution so that the potassium chlorate dissolves? Potassium chlorate has the same solubility as potassium chloride at boiling point.

[Bonny]

You can make potassium perchlorate from potassium chlorate with the jewelry trade platinum plated anodes. I did this several times. They do erode quickly due to the chlorate concentration dropping too low, and yes I did burn up several platinum plated anodes.

 

If I remember correctly Swede tried putting chlorate crystals inside a tube or something into the cell with the hope that it would continue to dissolve on its own, keeping the chlorate levels up, but was unsuccessful.

 

I had a few ideas to try but just never found the time.

 

1) A plastic mesh bag filled with the chlorate crystals. This would be placed in the cell under an air bubbler. The rising air bubbles (might) help dissolve the potassium chlorate on a continuous basis, reducing anode erosion.

 

2) A "feed cell" filled with a saturated solution of KClO3. Extra KClO3 would be added and the stirred on a regular basis to keep it saturated. This would be set up beside the perc cell. A timed (or maybe continuous) pump would pump the solution into the perc cell. The return pipe (or overflow) could simply drain by gravity back into the chlorate cell.

 

In theory, one or both of these methods could help keep the chlorate concentration high enough to prevent costly anode erosion...

 

The big problem would be that run time calculations could not be done, as the cell would be continuously refreshed with chlorate. The KClO4 would have to be harvested and cleaned thoroughly as the solution would still contain high levels of KClO3.

 

I'd like to try this if I ever get the time.

[ddb]

I have recently come across the following page to make AP from KP:

 

http://www.oocities.org/capecanaveral/campus/5361/chlorate/ammper5.html

 

The basic idea is to dissolve KP and Ammonium Sulfate under a high temperature and boil off the water until a paste forms containing AP and Potassium Sulfate. Ethanol is then used to dissolve the AP which is then evaporated to leave ery pure AP.

 

I have tried this method and I believe I have managed to get a small crop of AP (a few grams). I tested this with a simple AP/Charcoal mix which burnt with a characteristic deep yellow flame. I tried the solute and it did not burn nearly as well.

 

Now, my question relates to the ethanol used to dissolve away the AP. Based on the solubility of AP in Ethanol, I would need 100 ml for 2 grams of AP. This seems rather excessive. I was thinking of cooling the Ethanol down to precipitate the AP, allowing me to reuse the Ethanol. Otherwise I will have to distill it which is slow and inefficient.

 

Any thoughts?

[taiwanluthiers]

that sounds complicated...

[WSM]

What about heating the solution so that the potassium chlorate dissolves? Potassium chlorate has the same solubility as potassium chloride at boiling point.

The higher the temperature, the more it affects everything in the mix, including the perchlorate. It would be nice if it were selective or specific, but heat isn't.

 

WSM

Edited July 23, 2014 by WSM

[Mumbles]

A soxhlet extractor would be ideal for getting the AP out of the potassium sulfate.

[schroedinger]

A soxhlet extractor would be ideal for getting the AP out of the potassium sulfate.

God idea, but who got one of the right size? I would assume that need to have a 500 ml extractor for some reasonable ammounts.

 

Btw. AP got a solubility of 57.1 g/100ml at 100ºC where as Pottasium sulphate has just 24.3 g. At 0ºC its 11.56 vs. 7.4. So why not just do a fractional cristallisation?

 

But i think much more interesting would be the use of ammonium persulfate, as pottasium persulphate has just 4.7g at 20ºC. When chilled you should get quite pure ap to stay in solution and the pottasium salts should drop out. I would work with an excess of pottasium chlorate, to make sure no persulphate stays in solution. Then purify once by recristallisation

[WSM]

You can make potassium perchlorate from potassium chlorate with the jewelry trade platinum plated anodes. I did this several times. They do erode quickly due to the chlorate concentration dropping too low, and yes I did burn up several platinum plated anodes.

If I remember correctly Swede tried putting chlorate crystals inside a tube or something into the cell with the hope that it would continue to dissolve on its own, keeping the chlorate levels up, but was unsuccessful.

I had a few ideas to try but just never found the time.

1) A plastic mesh bag filled with the chlorate crystals. This would be placed in the cell under an air bubbler. The rising air bubbles (might) help dissolve the potassium chlorate on a continuous basis, reducing anode erosion.

2) A "feed cell" filled with a saturated solution of KClO3. Extra KClO3 would be added and the stirred on a regular basis to keep it saturated. This would be set up beside the perc cell. A timed (or maybe continuous) pump would pump the solution into the perc cell. The return pipe (or overflow) could simply drain by gravity back into the chlorate cell.

In theory, one or both of these methods could help keep the chlorate concentration high enough to prevent costly anode erosion...

The big problem would be that run time calculations could not be done, as the cell would be continuously refreshed with chlorate. The KClO4 would have to be harvested and cleaned thoroughly as the solution would still contain high levels of KClO3.

I'd like to try this if I ever get the time.

 

I recall Swede mentioning how treating the perchlorate and solution with potassium metabisulfite would neutralize the chlorate and the breakdown products would be soluble and could be washed off the potassium perchlorate crystals with cool distilled water, leaving a very pure product.

 

I like the sound of that.

 

WSM

[WSM]

that sounds complicated...

 

Yes it does, but I suppose it all depends on the availability of AP in your area and how much you want it. If AP is unobtanium in your area, and you want and need it enough to make your own, I say, Go for it!

 

WSM

[WSM]

I have recently come across the following page to make AP from KP:

http://www.oocities.org/capecanaveral/campus/5361/chlorate/ammper5.html

The basic idea is to dissolve KP and Ammonium Sulfate under a high temperature and boil off the water until a paste forms containing AP and Potassium Sulfate. Ethanol is then used to dissolve the AP which is then evaporated to leave ery pure AP.

I have tried this method and I believe I have managed to get a small crop of AP (a few grams). I tested this with a simple AP/Charcoal mix which burnt with a characteristic deep yellow flame. I tried the solute and it did not burn nearly as well.

Now, my question relates to the ethanol used to dissolve away the AP. Based on the solubility of AP in Ethanol, I would need 100 ml for 2 grams of AP. This seems rather excessive. I was thinking of cooling the Ethanol down to precipitate the AP, allowing me to reuse the Ethanol. Otherwise I will have to distill it which is slow and inefficient.

Any thoughts?

 

One thing occured to me, the left over potassium sulfate (K₂SO₄) can be double exchanged, in solution, with calcium nitrate (Ca(NO₃)₂) solution which will drop out the calcium sulfate as a precipitate, leaving potassium nitrate in solution. The potassium nitrate can be dried and crystallized, then ground to powder.

 

K₂SO₄ (aq) + Ca(NO₃)₂ (aq) > CaSO₄ v + 2KNO₃ (aq)

 

Even the calcium sulfate can be used as a color donor for orange strobes or stars (wash it well, though).

 

Better living through chemistry!

 

WSM

Edited July 24, 2014 by WSM

[WSM]

A soxhlet extractor would be ideal for getting the AP out of the potassium sulfate.

 

What type of thimble would be best? Actually, besides extracting organics from botanicals, I've never considered using a soxhlet extractor in such a way (especially for inorganic compounds).

 

Wow, have I lived a sheltered life! Thanks for opening my eyes, Mumbles.

 

WSM

Edited July 24, 2014 by WSM

[Mumbles]

I've used cellulose and glassfiber filters in the past. They both work about the same for applications like this. I find cellulose fibers to be stronger when dry, and glassfiber stronger when wet. Cellulose is probably considerably cheaper, but Glassfiber is also considered reusable. You can almost certainly reuse cellulose thimbles though. One trick is to let them dry in the extractor before removing them. Cellulose is compatible with most normal things we'd use. Just watch out for strong oxidizing agents and strong acids and bases. The only thing that might cause an issue here is possibly any remaining dichromate additives, unless you somehow generate perchloric acid or a bunch of hydroxide.

[ddb]

A soxhlet extractor would be ideal for getting the AP out of the potassium sulfate.

 

I never knew about this device, but it seems perfect! I'm in South Africa so getting one might be tricky. I might have to build my own.