making potassium (per) chlorate

[kingkama]

My CHLORATE cell has gone green . What causes this ???

 

An iron contamination of salt and acid could give a green coloring. I had a violet contamination that turned green when acidifing the brine. Edited March 12, 2022 by kingkama

[WSM]

An iron contamination of salt and acid could give a green coloring. I had a violet contamination that turned green when acidifing the brine.

 

 

Possibly a titanium salt?

 

WSM

[kingkama]

 

 

Possibly a titanium salt?

 

WSM

Possibile, but i think Is a complex of iron salts, possibile sulfate and chloride, they come imo from the HCl source i use for pH control. these salts become a brown precipitate if the environment is alkaline if acidic they disappear and oxidize creating black iron oxide on the cathodes.

[WSM]

Yeah, the KCl water softener seems to be reasonably pure. I recrystallize once with distilled water and the solution left over is saved and used for rinsing the harvested crystals of the next batch from the cell electrolyte. It seems to be a good start for cleaning the crystals of the next batch given it should be saturated in chlorate from the recrystallization of the previous batch (at ~ 0C) and therefore should not dissolve more chlorate. Overall, purification is a rinse with the said solution (chilled to almost 0C) and then the cleaned crystals recrystalized. I do heat them to about 120-150C after they have mostly dried to make sure no hypochlorite remains.

 

 

I've noticed a strong odor of chlorine (hypochlorite) in my sodium chlorate crystals harvested from electrolyte at 0^oC, but after a few days of air-drying on filter paper (on a glass plate) at room temperature, the chlorine smell disappears. I suspect the residual hypochlorite is unstable enough to break down during the drying step, leaving the sodium chlorate reasonably pure.

 

[NOTE: If you do something similar to what I've described above, be aware of the extreme flammability of the dry filter paper! Handle it carefully and dispose of it in a safe manner. If doing so by burning, do so in very small increments remotely. It can burn explosively in bulk! Use CAUTION.]

 

If you're making potassium chlorate from potassium chloride, the KClO₃ drops out of solution at room temperature, as it's formed due to it's lower solubility than the KCl electrolyte (no need to chill it down to 0^oC).

 

If you're making potassium chlorate from sodium chloride, why? With a decent set of electrodes (MMO and titanium), you can directly go from KCl solution to KClO₃!

 

Maybe I'm not understanding your setup . Please clarify if I'm wrong.

 

WSM

 

EDIT: Oh, I see. I reread your previous post about saving sodium chlorate electrolyte, and making some potassium chlorate to harvest that chlorate. Never mind my confusion, I understand.

Edited March 27, 2022 by WSM

[WSM]

I definitely wouldn't toss it if it is loaded with valuable sodium chlorate. It would be good to know how the hypochlorite decomposes under these conditions. At boiling temperatures it is of course fast and some chlorate / chloride is produced. As far as the electrolysis process goes, this doesn't set you back really because its a disproportionation reaction in chlorine and the overall oxidation (oxidation sum) in solution remains the same. I'm sure some is lost through other reactions taking place, but the chlorate should be stable. Not that it matters as much for a potassium cell due to the low solubility of potassium chlorate, but it has been a few months since I have used the electrolyte (stored in a HDPE bottle) and it went completely clear as per my eyes and chlorine scent was hardly present. I re-loaded it with KCl a few days ago and started the cell about 13 hours ago. The solution is dark yellow / green again, as I expected. Some KClO3 has already precipitated.

 

 

Thank you, I see what you mean and I agree.

 

I have no plans to toss the old electrolyte. I DO plan to recharge it for a subsequent run/runs. With all the precursor ions in there, follow-up runs will produce more chlorate in less time because less energy is spent making the precursors, and just producing more chlorate.

 

WSM

[WSM]

I have a knee surgery planned in the near future (torn meniscus, not replacement thank goodness), so I'll be off work for an extended time till I fully recover. My hope is to be able to clean up my research area in the back yard and get back to some electrochemistry experiments.

 

When I last worked at my experimentation, I was making a good size batch of concentrated potassium chloride solution. My intention was and is to purify it by filtration and contaminant removal, then neutralize the pH, preparatory to using the KCl solution for either electrolyzing to KClO₃ or using some to react by metathesis to form pure KClO₄ from NaClO₄ solution, made several years ago and stored.

 

Since I purified in similar fashion the sodium chloride solution (brine) I used to make my home made sodium chlorate crystals, I thought it wise to also purify my potassium salt solutions, to help make my end products as pure or purer than commercially available oxidizer salts.

 

Making chlorates and even perchlorates safely on an amateur basis is possible if we take proper measures and stick to good lab practices. Since we are making enough effort to make them at all, why not take the extra steps to make them of the highest quality possible?

 

My goal is not just to make some oxidizers (proof of concept), but to attempt to make some high quality materials useful for any of our pyrotechnic aspirations (rockets, color stars, whistle and strobe compositions, et cetera) that are first rate plus safe in storage and use. I've begun to see how we can do this and my efforts are focused on demonstrating and then describing processes to accomplish those goals.

 

If anyone sees or knows of improvements I can try, please share your thoughts here so we all will benefit from the discussion. Thank you.

 

WSM

Edited March 27, 2022 by WSM

[Arthur]

https://iopscience.iop.org/article/10.1149/1.2411796/pdf

[WSM]

https://iopscience.iop.org/article/10.1149/1.2411796/pdf

 

 

This article appears to be referencing State-of-the-Art about 1969. It's good reference material from that period.

 

WSM

[Arthur]

It does! It is a historic article, but few experimenters are even this good.

 

The important take away point is that professionally even with a Lead Dioxide anode there is a need to start the chlorate to perc stage with a saturated solution of sodium chlorate (900g/l) which is impossible directly from a chlorate cell liquor or a potassium cell.

[Arthur]

https://en.wikipedia.org/wiki/Solubility_table

 

Useful table of lots of solubilities in grams per 100ml

 

Someone else can work out how much KPerc soln will yield a kilo of perc and how much NaCl solution is needed to give that perc.

 

My theory is that KChlorate can be made KCl but perc must be made by the sodium route.

[WSM]

It does! It is a historic article, but few experimenters are even this good.

The important take away point is that professionally even with a Lead Dioxide anode there is a need to start the chlorate to perc stage with a saturated solution of sodium chlorate (900g/l) which is impossible directly from a chlorate cell liquor or a potassium cell.

 

 

This is true and why I harvest relatively pure sodium chlorate crystals from my sodium chlorate cell liquor, to dry and reserve for making saturated electrolyte for my perchlorate cell runs.

 

The highly charged "spent" sodium chlorate cell liquor is recharged with more sodium chloride and then used for subsequent runs, which produce more sodium chlorate in less time than the initial run, due to the load of precursor ions already in it. This can be amplified by using pH control which adds dilute hydrochloric acid to maintain the ideal pH (6.8) for the "bulk reaction" within the cell, where chlorate is formed throughout the cell rather than just between the electrodes, by "brute force", to quote Swede.

 

WSM

Edited April 11, 2022 by WSM

[WSM]

https://en.wikipedia.org/wiki/Solubility_table

Useful table of lots of solubilities in grams per 100ml

Someone else can work out how much KPerc soln will yield a kilo of perc and how much NaCl solution is needed to give that perc.

My theory is that KChlorate can be made KCl but perc must be made by the sodium route.

 

 

Potassium perchlorate has been proven possible to be made from potassium chlorate, but the effort and energy to do so is impractical, especially in a commercial setting.

 

My own conclusion is to follow the commercial method of using sodium salts to produce perchlorates, but I find the direct making of potassium chlorate from potassium chloride using an MMO anode with titanium cathodes very practical (nearly trivial), and my preferred method. The sodium route for making potassium chlorate would be unnecessary and impractical.

 

WSM

 

Edit: In all fairness, perhaps Arthur might say, "My theory is that potassium chlorate can be made from KCl but perchlorate aught to be made by the sodium route".

Edited April 11, 2022 by WSM

[Arthur]

Not quite!

I totally endorse making K Chlorate from KChloride. Electrolyse filter recharge repeat. Easy reliable and practical in large or small quantities.

For Perc though electrolysing NaChlorate at about 900g/l is far easier on the electrodes than electrolysing KChlorate at 73g/l solubility. With all of us baulking at the cost of a decent solid platinum electrode the sodium route offers an easier life and a longer life for an expensive electrode.

 

Another helpful part of the solubility numbers is that sodium chloride's solubility is relatively constant with temperature but the solubility of sodium chlorate varies a lot with temperature meaning that a good amount of Nachlorate will ppt out and crystalise out when chilled making the harvest easy.

 

Probably most of the attention needed is to keep the perc cell an easy environment for it's electrodes

Edited April 11, 2022 by Arthur

[WSM]

Not quite!

I totally endorse making K Chlorate from KChloride. Electrolyse filter recharge repeat. Easy reliable and practical in large or small quantities.

For Perc though electrolysing NaChlorate at about 900g/l is far easier on the electrodes than electrolysing KChlorate at 73g/l solubility. With all of us baulking at the cost of a decent solid platinum electrode the sodium route offers an easier life and a longer life for an expensive electrode.

Another helpful part of the solubility numbers is that sodium chloride's solubility is relatively constant with temperature but the solubility of sodium chlorate varies a lot with temperature meaning that a good amount of Nachlorate will ppt out and crystalise out when chilled making the harvest easy.

Probably most of the attention needed is to keep the perc cell an easy environment for it's electrodes

 

 

When I ran my giant (> 5 gallon or ~22 liters) sodium chlorate cell, the chlorate produced was dissolved in so much water that I could only retrieve a portion of it by chilling the electrolyte (about 3 liters at a time) in a refrigerator set to 0^oC. The remaining dissolved chlorate, plus chlorite, hypochlorite and chloride are still in the electrolyte, waiting to be recharged with more chloride and then run again.

 

My sodium chlorate (harvested) yield from the 6 week run was about 5 Kg. I tried various arrangements of plumbing options during the run, but it ended up as a batch system rather than semi-continuous like I was trying to do it. My first two runs were planned to be without pH control and the following runs were planned to have pH control, to observe the difference.

 

After that first run of my sodium chlorate cell, a friend shared a patent describing running a sodium chlorate cell much hotter, which would be more efficient and produce larger amounts of chlorate in less time. After considering the benefits vs effort, I decided to alter my original plans and adopt the enhanced methods described in the patent, on a small scale (a 5 liter cell with ~4 liters of electrolyte).

 

The plan is to run the cell with larger electrodes at about 110^oC, which will naturally concentrate the chlorate concentration of the electrolyte by evaporating the water during the run. The described benefits include the sodium chlorate dropping out of solution at room temperature rather than requiring refrigeration, amongst other positive effects.

 

My efforts to duplicate the high temperature system drove me to using a 5 liter borosilicate glass reaction vessel with a large gasketed opening for the cell. I've built a stand to hold the cell with a ~25mm thick plate of PTFE polymer clamped on for a lid. I need to design the cell lid and figure out how many, where and what size of tapped holes to add for plumbing the cell fittings for the electrodes, a vent plus various sensors and ports for sampling plus hot electrolyte removal and adding brine to replenish the system.

 

It's all very exciting to contemplate such an efficient system, if it works as well as I hope it will.

 

Now, once I can produce a large enough supply of pure sodium chlorate crystals, I hope to continue my perchlorate experiments and see where I want to go from there...

 

WSM

[mx5kevin]

The homemade chlorate and perchlorate project

 

This is my NaClO4, KClO4, NaClO3, KClO3, NH4ClO4 setup. Tutorials with videos, documents and links for homemade chlorate and perchlorate production.

[Arthur]

One Electrochemical Society paper that I read said that the chlorate cell was always topped up to level with saturated brine with additional HCl as required to keep the pH optimal. Needing two dosing pump systems for the cell. The benefit of this is continuously having a full cell and continuously having enough chloride in the cell. If you run the cell to near completion, then increase the replenishment rate, the overflow will be available to precipitate out the chlorate and filter, returning the liquor upstream and the crystals downstream.

[WSM]

One Electrochemical Society paper that I read said that the chlorate cell was always topped up to level with saturated brine with additional HCl as required to keep the pH optimal. Needing two dosing pump systems for the cell. The benefit of this is continuously having a full cell and continuously having enough chloride in the cell. If you run the cell to near completion, then increase the replenishment rate, the overflow will be available to precipitate out the chlorate and filter, returning the liquor upstream and the crystals downstream.

 

 

After thoughtful consideration, I agree (for a continuous system, which your description appears to be).

 

I haven't gotten to that point yet, but I see where the high temperature sodium chlorate cell will readily lend itself to such a system, with the proper sensors and monitoring added in. If a crystallizer section is added to the basic cell, yes.

 

WSM

[WSM]

Not quite!

I totally endorse making K Chlorate from KChloride. Electrolyse filter recharge repeat. Easy reliable and practical in large or small quantities.

For Perc though electrolysing NaChlorate at about 900g/l is far easier on the electrodes than electrolysing KChlorate at 73g/l solubility. With all of us baulking at the cost of a decent solid platinum electrode the sodium route offers an easier life and a longer life for an expensive electrode.

Another helpful part of the solubility numbers is that sodium chloride's solubility is relatively constant with temperature but the solubility of sodium chlorate varies a lot with temperature meaning that a good amount of Nachlorate will ppt out and crystalise out when chilled making the harvest easy.

 

Probably most of the attention needed is to keep the perc cell an easy environment for it's electrodes

 

 

I fully subscribe to the last statement in Arthur's post.

 

As they became available at times in the past (nearly a decade ago at this point), I acquired (beta-form) lead dioxide coated CP titanium mesh anodes, and a few platinized (platinum plated) CP titanium mesh anodes.

 

As others had attempted to use the same LD anodes and failed due to the LD coating spalling off of the titanium during their attempted runs, I held off using them till I could find a way to do so safely (and not destroy them in the attempt). Then, as Arthur has said, I came to the conclusion to "keep the perc cell an easy environment for it's electrodes".

 

I imagined the failure of others in using the very same electrode (of Chinese origin), was due to their mistreating the lead dioxide electrodes. I guessed they treated them the same as MMO electrodes and used higher voltage and current than they needed, and caused the electrodes to fail prematurely.

 

Wanting to avoid such a fate for my expensive and hard-to-find LD anode, I determined in my first run to "go easy" on it. Instead of loading the electrode at 0.3 Amperes per square centimeter of it's area, I used a small, lab grade DC power supply with CV and CC capability (constant voltage, constant current), and ran the perchlorate cell with about 0.1 Ampere per square centimeter, and it worked! Also, an added bonus was, by running the cell in constant current (CC) mode, I found that calculating the theoretical end-of-run time, was simplified.

 

Another comment/clue from those running the same anode, but with heavier current, was they noticed strong ozone emissions from their cell during the run. I noticed a mild ozone odor emanating from the vent of my cell during it's run which was not overpowering but more like "fresh air" (not unpleasant at all), if my recollection is correct.

 

There is more about my successful first attempt to make perchlorate from sodium chlorate electrolyte (over six years ago), that I won't mention at this time; so I don't take away from the main point of running perchlorate cells differently from chlorate cells.

 

WSM

Edited May 30, 2022 by WSM

[WSM]

Reading this Topic can be a daunting task at it's current length of 270 pages.

 

The Topic, "The Bucket Cell..." started about ten years ago by "Swede", is an easier read at it's current length of just 22 pages, and covers some basic details as well as other facets of oxidizer home production.

 

Some of the discussion is more applicable to beginners and most posters are approachable there as well as here.

 

Sure there are more advanced projects and ideas (plus vast quantities of minutia) in the Topic here, but the Topic there is geared more toward a simpler approach to making and running small, amateur potassium chlorate cells. The potential to make respectable amounts of useful oxidizers, safely and in a reasonable amount of time exists using smaller containers.

 

WSM

[dangerousamateur]

Hi guys,

 

maybe I'll get a little bit ahead this fall.

 

I was just thinking a little and some questions emerged...

 

Do you guys have a kind of temperature control for your cells?
So that you have lets say constant 60 degrees celsius or something like that?

Do you find a stirring system inside the cell to be helpful?
Or do you think this is BS because the heat causes enough movement anyway?

If I buy a power supply with a range from 4,8 to 5,3V, is this enough range for typical cells?
If you have the choice, what range should the perfect power supply have (just chlorate)?

[WSM]

Hi guys,

 

maybe I'll get a little bit ahead this fall.

 

I was just thinking a little and some questions emerged...

 

Do you guys have a kind of temperature control for your cells? No, not for smaller cells. They're usually somewhat self-regulating.

So that you have lets say constant 60 degrees celsius or something like that? Anywhere between 20^oC and 60^oC works.

 

Do you find a stirring system inside the cell to be helpful? Not yet.

Or do you think this is BS because the heat causes enough movement anyway? If the leads are long enough to place the electrodes low in the cell, convection-like currents will encourage proper mixing by heat and "hydrogen lift" (hydrogen bubbles off the cathode). If the electrodes are near the top of the cell, thermal layering (and poor mixing) is usually seen.

 

If I buy a power supply with a range from 4,8 to 5,3V, is this enough range for typical cells? Voltage-wise, yes; but Current (Amperage) is the main driving force in electrochemical cells. Read the blog, "Homegrown Oxidizers Parts 1-4", for more details on designing potassium chlorate cells.

If you have the choice, what range should the perfect power supply have (just chlorate)? 3-6 Vdc and as much current as you can afford (typically, the higher the available Amperage, the higher the cost of the power supply). For experimentation, a supply with constant voltage (CV) and constant current (CC) capability is useful.

 

 

I hope the answers (in red above) are helpful.

 

WSM

Edited August 29, 2022 by WSM

[Arthur]

Online suppliers can usually find a Meanwell brand (Chinese) smpsu of 5v+/- % and up to 60a For a first cell don't try to exceed 20a without serious calculations and adequate cable sizes. I found a swing needle direct reading ammeter reading up to 50A cheaply.

[dangerousamateur]

Thank you. Constant current is out of my budget.

 

But I see that most amateur cells have no current limiter.

 

 

Electrode spacing is the only limiter, correct?

Does that always work out OK?

The electrodes most be securely fixed in place of course.

 

 

With a maximum of only 5,3V, will I need an extremely tight electrode spacing with typical cells, or is that still no problem?

I would rather chose more adjustment range, but perhaps this is unjustified.

[Arthur]

You can certainly lose some current by using longer leads. Short leads have low resistance longer leads have higher resistance at the currents involved 10 milli ohms is a reasonable current limiter. Copper covered aluminium is higher resistance than pure copper of the same size

 

https://www.ebay.com/itm/224781949981 May be interesting but may be 230vac.

https://www.ebay.com/itm/265854333787 cheap but 5A max.

Other options exist!

 

Remember that overdriving the electrodes (esp the anode) will stop things working.

Edited August 29, 2022 by Arthur

[WSM]

Thank you. Constant current is out of my budget.

But I see that most amateur cells have no current limiter.

Electrode spacing is the only limiter, correct?

Does that always work out OK?

The electrodes most be securely fixed in place of course.

With a maximum of only 5,3V, will I need an extremely tight electrode spacing with typical cells, or is that still no problem?

I would rather chose more adjustment range, but perhaps this is unjustified.

 

 

The spacing matters more in a large/industrial system. In an amateur cell, it appears to be less critical, especially if pH control is used.

 

I prefer to spot weld my electrodes to titanium leads. I always seek out CP titanium (that's Commercially Pure) for cathodes and leads inside the cell.

 

Once you have a power supply and electrodes, run a cell and learn how it works.

 

WSM