making potassium (per) chlorate

[WSM]

For an experiment in making sodium chlorate (feed stock for perchlorate cells) I'm adapting a small power supply I bought on eBay a year or two ago.

 

It measures 2" x 4.5" x 9" long (~50 mm x 112 mm x 225 mm), has a voltage adjust and is rated at 5 Vdc and 55 A. The adjustment range is 4.20 V to 5.84 V. The terminal block has nine positions, three for AC power input (line, neutral and ground) and three each for positive and negative outputs.

 

 

I plan to run three pairs of 12 AWG wires from the outputs to two solid copper bus bars, 1/8" x 7/8" (3 mm x 22 mm), which will easily carry the current. I'll bolt the cell leads from the bus bars to the cell electrodes, hopefully in a nice, tidy arrangement.

 

If this power supply works, great! If not, I have a few back up options. We'll see...

 

WSM

Edited July 13, 2015 by WSM

[WSM]

I found a source for LCD panel meters with double displays, both voltage and amperage.

 

I fabricated a box with a 200 Volt, 200 Amp DC meter and coupled it with an LCD temperature meter.

 

 

All that remains to be done is harden the temperature sensor against harsh environments. To do so, I'm still deciding whether to use PVDF shrink tube or thin walled Viton tubing.

 

The beauty of a display like this is it'll work for a wide variety of setups, plus it runs both meters from a single power source.

 

WSM

Edited July 29, 2015 by WSM

[MadMat]

In the past I worked in the lab at an electroplating co. So, even though Im not an expert in specifically making perchlorate, I have done a lot of reading on the subject and understand whats going on. First off, Lead dioxide anodes seem to be the best choice. There are a few parameters that you need to follow. The electrolyte solution needs to be kept at a slightly acidic ph (around 5.0-5.5). The ratio of anode to cathode surface area is important. Remember you are trying to oxidize chloride into chlorate/perchlorate. It may sound counter-intuitive but you need a larger surface area on your cathode (this equals a smaller current density on the cathode and a higher current density on the anode). If it is the other way around you will reduce your precious chlorate/perchlorate ions back to chloride at the cathode. Another thing is to add a small percentage of sodium flouride to the electrolyte. This does two things; it further decreases the reduction of the chlorate/perchlorate at the cathode and it prevents polarization of the anode. Polarization of the anode becomes apparent when the current drops reduces (for no apparent reason). You can further test this by reversing the polarity on your cell and see a dramatic increase in the current flowing at the same voltage. Anode polarization is also the reason the electrolyte needs to be kept acidic. Important!!! sodium flouride is some real nasty stuff; solutions of it will etch glass and absorb through the skin. If you choose to use carbon anodes, replace the sodium flouride with sodium/ potassium dichromate, it will serve the same function as the sodium flouride but is more suitable for carbon anodes. With lead dioxide anodes, sodium dichromate will produce icky chromates and actually encourage polarization of the anode, so don't use it with lead. I am actually going to start some experiments myself with a perchlorate cell in the very near future and see what I can come up with.

[MadMat]

One more thing on the subject of power supplies. An old power supply out of a pc should work nicely. To turn it on just connect the green wire to a black wire. Most supplies have a list on them telling the voltages of the various colored wires. And for those with limited knowledge of electronics, it is a bi-polar supply so you will find things like a +12 and a -12 v. This simply represents what the polarity of that wire is in relationship to the black (ground) wires.

[WSM]

In the past I worked in the lab at an electroplating co. So, even though Im not an expert in specifically making perchlorate, I have done a lot of reading on the subject and understand whats going on. First off, Lead dioxide anodes seem to be the best choice. There are a few parameters that you need to follow. The electrolyte solution needs to be kept at a slightly acidic ph (around 5.0-5.5). The ratio of anode to cathode surface area is important. Remember you are trying to oxidize chloride into chlorate/perchlorate. It may sound counter-intuitive but you need a larger surface area on your cathode (this equals a smaller current density on the cathode and a higher current density on the anode). If it is the other way around you will reduce your precious chlorate/perchlorate ions back to chloride at the cathode. Another thing is to add a small percentage of sodium flouride to the electrolyte. This does two things; it further decreases the reduction of the chlorate/perchlorate at the cathode and it prevents polarization of the anode. Polarization of the anode becomes apparent when the current drops reduces (for no apparent reason). You can further test this by reversing the polarity on your cell and see a dramatic increase in the current flowing at the same voltage. Anode polarization is also the reason the electrolyte needs to be kept acidic. Important!!! sodium flouride is some real nasty stuff; solutions of it will etch glass and absorb through the skin. If you choose to use carbon anodes, replace the sodium flouride with sodium/ potassium dichromate, it will serve the same function as the sodium flouride but is more suitable for carbon anodes. With lead dioxide anodes, sodium dichromate will produce icky chromates and actually encourage polarization of the anode, so don't use it with lead. I am actually going to start some experiments myself with a perchlorate cell in the very near future and see what I can come up with.

 

 

It sounds like several different theories are jumbled into one. Maybe some of this post needs to be clarified.

 

A couple of observed issues:

 

"Slightly acidic" is just below a pH of 7.0 (CAUTION: 5.0-5.5 is too acidic and will pump chlorine gas out of a chlorate cell!)

 

If your anode is plated on CP titanium, fluorides will attack the electrodes and render them unusable before long*. An LD coated graphite anode can survive but avoid higher temperatures.

 

I look forward to hearing more about your perchlorate cell experiments and how things turn out. I'm fascinated by the process.

 

WSM

 

Edit: *Ample documentation exists showing that fluorides aggressively attack titanium and cause severely diminished effectiveness and longevity in titanium based electrodes. The suggestion to add NaF to the electrolyte is usually associated with GSLD (graphite substrate lead dioxide) anodes, and certainly not advised where titanium is used. We need to know our materials, with their strengths and limitations, to effectively use them.

Edited August 1, 2015 by WSM

[WSM]

One more thing on the subject of power supplies. An old power supply out of a pc should work nicely. To turn it on just connect the green wire to a black wire. Most supplies have a list on them telling the voltages of the various colored wires. And for those with limited knowledge of electronics, it is a bi-polar supply so you will find things like a +12 and a -12 v. This simply represents what the polarity of that wire is in relationship to the black (ground) wires.

 

Lots of folks have had success using re-purposed computer power supplies for powering chlorate cells. I fear that using them to make perchlorates by the Chinese made LD anodes I'm using (which are LD on titanium) would compromise their integrity and cause them to fail (several others have reported these LD anodes coming apart in fairly short order when powering them with "uncontrolled" power supplies).

 

I've had very good (perchlorate cell) performance so far, using a regulated DC power supply running in constant current (CC) mode. If you're able to do something similar, I highly recommend it.

 

WSM

Edited August 1, 2015 by WSM

[Arthur]

It seems that the chlorate cell is largely mastered with DSA and Ti electrodes, Yes you can cram a lot of electricity into them -but you need to because of the electrochemistry.

 

With the PERC cell, I've heard that only pure Pt works as an electode, but WSM has found a way to use platinum coated electrodes with a controlled current supply.

 

Maybe a repurposed ATX PSU will work for the chlorate production even if a constant current PSU is needed for conversion to perc.

[WSM]

It seems that the chlorate cell is largely mastered with DSA and Ti electrodes, Yes you can cram a lot of electricity into them -but you need to because of the electrochemistry.

1) With the PERC cell, I've heard that only pure Pt works as an electode, but WSM has found a way to use platinum coated electrodes with a controlled current supply.

2) Maybe a repurposed ATX PSU will work for the chlorate production even if a constant current PSU is needed for conversion to perc.

 

A few minor points of clarification:

 

1) pure platinum works, but the work is done on the surface of the electrode so plated or clad platinum surfaces work also. I didn't discover this, it's used widely in industry as well as laboratories. I gleaned the information about controlling the current from many publications and posts I've studied (most of which have been linked or posted here and elsewhere) and when I applied it in my experiments, they proved to be true, so far.

 

2) many folks have used computer power supplies to make chlorates successfully. I haven't because I have access to other types and configurations of DC power supplies, which I've gained experience and confidence in using, so I use them. I'd use a modified computer supply also, if I didn't have the others.

 

I think my success in experimentally making perchlorate, using commercially available platinized titanium or LD coated titanium anodes, is largely due to limiting the current using a DC power supply with a controllable output. From my observations, the supplied current for the perchlorate systems is better applied with a feather than a hammer, where the chlorate systems are vastly more forgiving. We'll see if this is always the case or whether other types of perchlorate anodes in the future will be hardier and able to withstand a heavier hand, power wise.

 

WSM

Edited August 1, 2015 by WSM

[MadMat]

Yeah, I guess I have combined a few things. Some of which were taken from my electroplating experience, namely chrome plating as it uses lead dioxide anodes. The difference being in chrome plating the anodes are solid lead that have been electrolyzed in a mild (10%) sulfuric acid solution. This process forms lead dioxide on the surface on the lead. This is going to be one of my first attempts in my experiments. In chrome plating fluoride is used as a catalyst for the plating process, and it helps keep the anodes from polarizing.

Edited August 1, 2015 by MadMat

[WSM]

Yeah, I guess I have combined a few things. Some of which were taken from my electroplating experience, namely chrome plating as it uses lead dioxide anodes. The difference being in chrome plating the anodes are solid lead that have been electrolyzed in a mild (10%) sulfuric acid solution. This process forms lead dioxide on the surface on the lead. This is going to be one of my first attempts in my experiments. In chrome plating fluoride is used as a catalyst for the plating process, and it helps keep the anodes from polarizing.

 

Your description sounds like you're making alpha-form lead dioxide on the lead plates.

 

The chlor-alkali literature I've researched specifies using beta-form (hard crystalline) lead dioxide for perchlorate manufacture; stating it's superior to alpha-form for the purpose. I wonder how the alpha-form will hold up in an operating perchlorate cell?

 

WSM

Edited August 1, 2015 by WSM

[MadMat]

Well I'll find out soon how the alpha lead dioxide holds up. BTW it wont be a plate. I cast out a 1/2 diameter x 6" long lead rod with a 12 guage copper wire about 2.5" long running down the middle of it. My first attempt will consist of a saturated NaCl solution with approx 250-300 ppm sodium flouride added. I will start it out at a Ph of 5.5-6.0. adjusted with HCl as necessary. I plan on using either mild steel or stainless steel for the cathode; haven't quite decided yet. Actually, thanks for bringing the alpha/ beta forms of lead dioxide to my attention. After a little reading it appears I can control the formation of alpha or beta lead dioxide through adjusting the parameters of temperature and current density; or possilby using an electrolyte other than sulfuric acid. Though beta PbO2 is desirable, Alpha PbO2 does have some desirable qualities as well, namely, lower electrical resistance and it is physically more durable, as Beta PbO2 tends to be brittle. More research is needed before I continue.

Edited August 2, 2015 by MadMat

[WSM]

Well I'll find out soon how the alpha lead dioxide holds up. BTW it wont be a plate. I cast out a 1/2 diameter x 6" long lead rod with a 12 guage copper wire about 2.5" long running down the middle of it. My first attempt will consist of a saturated NaCl solution with approx 250-300 ppm sodium flouride added. I will start it out at a Ph of 5.5-6.0. adjusted with HCl as necessary. I plan on using either mild steel or stainless steel for the cathode; haven't quite decided yet. Actually, thanks for bringing the alpha/ beta forms of lead dioxide to my attention. After a little reading it appears I can control the formation of alpha or beta lead dioxide through adjusting the parameters of temperature and current density; or possilby using an electrolyte other than sulfuric acid. Though beta PbO2 is desirable, Alpha PbO2 does have some desirable qualities as well, namely, lower electrical resistance and it is physically more durable, as Beta PbO2 tends to be brittle. More research is needed before I continue.

 

Excellent. Keep us informed of your progress.

 

The next time you need to cast a lead rod, you might try a tip I learned from the old days when they made lead sheathed cable. When the lead melt was hot enough, a guy would drop a small chunk of sodium metal in the melt. The sodium was a getter which would attract any oxides and form dross on the top of the melt. After skimming the dross off, a nice "pure" lead pour followed which looked like mercury (very clean) as it went into the mold.

 

WSM

[taiwanluthiers]

Getting sodium metal may be a problem as it can't be shipped at all.

[Mumbles]

Getting sodium metal may be a problem as it can't be shipped at all.

 

Not true.

[Differential]

Of course, if you can't get sodium, Lithium's a "getter" too. I remember reading in "The Radioactive Boy Scout" that David Hahn used lithium from rechargeable batteries to get elemental potassium from potassium chloride. You just don't want to buy a bunch of lithium batteries at once, to avoid attention from the DEA.

Edited August 3, 2015 by Differential

[taiwanluthiers]

Just be careful dismantling those lithium batteries...

[WSM]

Just be careful dismantling those lithium batteries...

 

If I were to bother dismantling lithium batteries, I think I'd do it under mineral oil. Even then, lithium metal will float on the oil.

 

WSM

[WSM]

My responses to postings may be spotty for the next two weeks. I'm going to the PGI Convention in Gillette, WY, to get my annual "pyro fix".

 

If you see me there, introduce yourself and say Hi.

 

WSM

[WSM]

Hi All,

 

I'm back from the PGI Convention, but nursing a horrible cold and sinus infection (Yuk). I spent most of my time in manufacturing and saw many friends (including some who frequent here).

 

Surprisingly, one fellow set up and ran a simple chlorate cell (it's always fun to meet a fellow enthusiast).

 

 

I believe he was selling kits at the Trade show, but have no idea how sales went. I got his contact information so we can stay in touch and share ideas.

 

WSM

[pyrokid]

Very interesting. Do you know what the price point and production rates were for those kits?

[WSM]

Very interesting. Do you know what the price point and production rates were for those kits?

 

No, but I can say his electrodes were not optimized. His anode was about 0.875" wide by about 5" long. The cathodes (plural) were 0.125" diameter titanium rods about 6" long. If you do the math, you may be able to calculate the rate.

 

WSM

[schroedinger]

Is he running the cell at 100ºC?

 

8.75 square inch anode area to 0.46 on the cathodes? There is a factor 20 missing! I bet the cathodes will get quite hot and will have quite a lot of ressistance.

Edited August 20, 2015 by schroedinger

[WSM]

Is he running the cell at 100ºC?

8.75 square inch anode area to 0.46 on the cathodes? There is a factor 20 missing! I bet the cathodes will get quite hot and will have quite a lot of ressistance.

 

No, he's running it at 44^oC.

 

It seems to work, even if the system is inefficient. He had several pounds of dried crystals from his cells to show for his efforts.

 

WSM

[Kevin]

This is my first post so be gentle with me

 

I apologize if this has been previously discussed, but I'm wondering what the recommended cathode thickness is for a chlorate cell. I'm planning to run with two cathodes sandwiching a 1" x 10" mmo anode (from laserred) at approximately 25 - 30 amps. I've found some (I think) decently priced grade two titanium sheets on ebay that are .040" and .041" thick. Would that be sufficient?

Thanks,

 

Kev

Edited August 22, 2015 by Kevin

[WSM]

This is my first post so be gentle with me

I apologize if this has been previously discussed, but I'm wondering what the recommended cathode thickness is for a chlorate cell. I'm planning to run with two cathodes sandwiching a 1" x 10" mmo anode (from laserred) at approximately 25 - 30 amps. I've found some (I think) decently priced grade two titanium sheets on ebay that are .040" and .041" thick. Would that be sufficient?

Thanks,

Kev

 

Hi Kev,

 

Welcome to the discussion. Our friend, Swede, used 0.040" CP titanium quite a bit, early on. Unless things seriously overheat, I see no problem using it.

 

If your cell is deep enough to handle the 10" long electrode, things should work out with one hitch: I estimate the total current demand of the anode with two matching cathodes to be 38.7 Amps. If your power supply outputs 30 Amps, maximum, it may overheat trying to keep up with your electrodes.

 

If you have the power supply already and aren't opposed to modifying the anode, try cutting it in half (I use either a hack saw or aircraft shears to cut laserred's anode material) and the total current demand will be 19.35 Amps which the 25-30 Amp power supply can handle without any problem.

 

Let us know if that works for you.

 

What size or type of cell body are you planning?

 

WSM