making potassium (per) chlorate

[WSM]

I'm progressing my sodium chlorate cell experiment. I've decided to set it up outdoors to avoid any chlorine or other odors inside.

 

I've plumbed the outside of the cell with a magnetically coupled chemical pump for moving the cell electrolyte without spillage. This is possible because everything is soluble and not prone to drop out as crystals without deliberate effort.

 

I was considering attaching a 5 gallon bucket by plumbing and pumps for a salt solution reservoir, but remembered a 33 gallon square polypropylene tank I acquired from a fortunate eBay find several years ago and dug it out, cleaned and dried it and plumbed it to the cell with valves and a second pump like the one described before.

 

 

With the setup organized like this photo shows, by various valving schemes, I can mix salt solution, stir the running cell or fill the cell from the salt solution tank. The beautiful thing about the chemical pumps is they consume only 5 Watts of power when they're running, and they're so quiet you have to touch them to tell they're running. They were a great find on eBay back when the photofinishing machines were surplussed due to the popularity of digital photography, and the price is a small fraction of new stock from the manufacturer.

 

I'm still working on making the DC power supply weather resistant, and I'm making good progress.

 

I'll show more as I get closer to running the cell and we'll see where this all leads.

 

WSM

Edited April 17, 2016 by WSM

[solkompleksowa]

Tried etching PCBs with HCl, and diluted H2SO4 and it's just been impossible without H2O2 (though Cu dissolves in acidic CuCl2 ([CuCl4]2-) and this might explain why it is slightly soluble in HCl)

and didn't notice any Cl2 gas (only O2 - decomposition of H2O2)

 

Anyway, great work WSM!

[MrB]

Please be careful about using acids and hydrogen-peroxide together. It's a very short step away from primary explosives, and even if one does take the precautions needed, the conversations with the government officials that may come as a result of purchasing the stuff in times of "terrorist threat" such as these may have their own... side effects. If you are not already on a watchlist... Well, just saying. ;- )

 

WSM, your ongoing efforts are a pleasure to behold. Thank you.

B!

[WSM]

Tried etching PCBs with HCl, and diluted H2SO4 and it's just been impossible without H2O2 (though Cu dissolves in acidic CuCl2 ([CuCl4]2-) and this might explain why it is slightly soluble in HCl)

and didn't notice any Cl2 gas (only O2 - decomposition of H2O2)

Anyway, great work WSM!

 

Etching PC boards?!! I forgot about using ferric chloride solution (though it works better HOT).

 

Maybe my HCl (pool muriatic acid) works better than reagent grade because it appears to be contaminated with a little iron. I wonder...

 

Thanks.

 

WSM

[WSM]

WSM, your ongoing efforts are a pleasure to behold. Thank you.

B!

 

Thanks MrB. I never originally planned on making sodium chlorate, but the path to making perchlorates and specialty chlorates has lead me here. Plus, the process has been it's own reward; I'm learning by designing every step (every new challenge seems to open paths and greater opportunities). I'm learning a lot and getting closer to being self sufficient for oxidizers.

 

If I were able to just make fireworks and shoot them, I would have never gone very far on this road. Maybe living in a city and in a fireworks un-friendly state, has created the fertile ground where all this creativity can blossom?! I've always been interested in chemistry and I've done more "real" chemistry than I ever thought I would during this project. It's been a fun adventure and I'm grateful for the creative outlet and education.

 

It's my pleasure to share, and we all learn together. (whew, after all that talk, this thing better work! )

 

WSM

[WSM]

I went out last night and found 13 gallons (49.2 liters) of distilled water to buy. I better start making my own distilled water or the cost of making oxidizers may start to mount up.

 

I added the water to the 40 pounds (18.1 kilos) of pure water softener salt (NaCl) in the brine tank, and plugged in the pump after valving for brine circulation. The pump ran over night (about 8 hours) and most of the salt dissolved. Because of cooler weather at night, it makes sense that more salt didn't dissolve.

 

I plan to start the pump again in the heat of the day and see where the salt level is by sundown, to see if most of it will be in solution.

 

My square brine tank is 18" by 18" by 24" tall (45.7 cm square by 61 cm high). I've calculated that at 20" high (50.8 cm), the volume is about 100 liters, and takes two 40 pound bags of salt (36.2 kilos) plus about 26 gallons (98.4 liters) of distilled water. It doesn't take up much space on the bench, but what a monster! It's a large reservoir. I'm glad I've plumbed it with tubing, valves and pumps so I don't have to handle all that liquid and weight by hand (I'm getting too old for that stuff). It's safer, too; especially when that salt water turns into a potent bleach (in the cell, of course)!

 

I'll add more as this develops...

 

WSM

Edited April 18, 2016 by WSM

[MadMat]

It's been a long time since I did any work on this (life has a way of taking time away from the fun things!) But soon, I will start my experiments with creating solid lead anodes and electrolyzing the lead dioxide coating. If successful, this will make it much cheaper and easier to home-brew potassium perchlorate. I just need to figure out how to create the right combination of alpha and beta forms of lead dioxide on the surface of the solid lead anode. My first experiments will test temperature variations while creating the lead oxide coating. I get this idea from the fact that temperature variations are what create the difference in the anodizing of aluminum. If the anodizing bath is kept around the freezing temperature of water, you get what is known as hard coat anodizing. I will post my results as I get them.

Edited April 19, 2016 by MadMat

[WSM]

Though my brine tank has more than 100 liters capacity, I've kept the volume of brine to about 50 liters, give or take. The cell needs about half that amount so 50 liters is plenty to start.

 

The clear vinyl tubing and polypropylene brine tank are suitable for brine but would be negatively affected by sodium hypochlorite, especially when hot (as when the cell is running). So my cell is constructed of hard PVC. Realizing the flexible vinyl tubing may be less than ideal for hot hypochlorite, I've got some PTFE (Teflon) tubing coming to replace those parts of the cell plumbing that will be in contact with the mother liquor. The rest of the plumbing is PVC, PVDF and polyethylene (buckets) which are listed as good with hot hypochlorite.

 

I'm modifying parts of my setup as I approach starting it up, for compatibility and function. I hope to start the system by next weekend. I still need to assemble my electrical system and add the sensors to the cell, plus plumb it for pH control in later runs (for comparison to the non-controlled initial runs).

 

When everything is set up and running, we'll see how the 44 Amp electrodes work out. If they seem too small for the job, I'm inclined to scale up even more; but we'll cross that bridge when we come to it. I have several options and will determine which way to go when we see how the initial system works out.

 

More (plus photos) later...

 

WSM

Edited April 23, 2016 by WSM

[WSM]

I added the water to the 40 pounds (18.1 kilos) of pure(?)water softener salt (NaCl) in the brine tank, and plugged in the pump after valving for brine circulation. The pump ran over night (about 8 hours) and most of the salt dissolved. Because of cooler weather at night, it makes sense that more salt didn't dissolve.

 

Yesterday I took a closer look at my brine. There appears to be a few large and dark pieces of stone or scale among some undissolved salt crystals on the bottom of the brine tank. I removed them with an aquarium fishnet and they are seen on a paper towel here:

 

 

I tested them with a small, strong magnet and most of them are somewhat magnetic. I believe the big pieces are rust from tanks or pipes from the salt plant and a couple others appear to be stones. Apparently, one should pick over the salt as with dried beans to remove foreign matter before soaking.

 

Besides the large dark chunks, there appears to be some dirt or silt on the bottom of the brine tank:

 

 

As the take-up port inside the brine tank is slightly off the bottom, I hope that the debris will stay behind when transferring liquids by valving (to the cell), otherwise a filtering scheme needs to be added to my setup. With this development, I wonder what else may be contaminating my brine, unseen?

 

Industry treats their raw brine with sodium hydroxide and sodium carbonate to remove calcium and magnesium contaminants by filtration, since the hydroxides and/or carbonates of those metals form flocculant precipitants. I was hoping to avoid that step, but may have to do the same if I want a pure product.

 

Nuts!

 

If I can find a truly pure salt without these contaminants (and the price is reasonable), my life will be a lot easier; otherwise I need to copy industry and treat my brine . I have a container of salt for saltwater pools, which should be cleaner, but is also a lot more expensive . I better try it next time and see if there's a difference

 

We'll see...

 

WSM

[WSM]

I forgot to mention that I modified my brine tank plumbing.

 

I noticed some salt crust around the lid and on the inside tank walls. The output of the pump was connected to a fitting on the lid of the tank, where the fluid would fall to the brine pool below. This caused a lot of splashing which, I believe, accounts for the salt deposits I was seeing.

 

I added a barb fitting to the inside port and ran a piece of vinyl tubing down to the brine surface (or just barely below it), and this appeared to solve the problem. It also helped the salt to dissolve better with all the added fluid flow, plus was so quiet (without the splashing sounds) that it was hard to tell the pump was running.

 

Step by step, this is all coming together.

 

WSM

[WSM]

The clear vinyl tubing and polypropylene brine tank are suitable for brine but would be negatively affected by sodium hypochlorite, especially when hot (as when the cell is running), so my cell is constructed of hard PVC. Realizing the flexible vinyl tubing may be less than ideal for hot hypochlorite, I've got some PTFE (Teflon) tubing coming to replace those parts of the cell plumbing that will be in contact with the mother liquor. The rest of the plumbing is PVC, PVDF and polyethylene (buckets) which are listed as good with hot hypochlorite.

WSM

 

The Teflon tubing arrived during the week and I was able to replace the vinyl tubing. First I modified the PVC plumbing to line up the fittings for straight runs of tubing to them (to minimize the use of more expensive and difficult to obtain materials).

 

Next I placed the flexible vinyl tubing in the fittings to seal the system (to keep dust and little creatures out). When the Teflon (PTFE) tubing arrived, I measured and cut the required lengths and replaced the vinyl with Teflon.

 

Teflon tube

 

Before (with clear, flexible vinyl tubing)

 

After (the vinyl is replaced with Teflon tubing)

 

I'll replace the vinyl tube in the portion of the plumbing dropping down to a holding tank (5 gallon bucket), when the proper PVDF fittings are delivered, so my electrolyte section of the system will be completely inert to the ravages of hot hypochlorite (electrolyte from a running cell).

 

My plans for the holding tank are to run the tubing down to the bottom of the bucket so the fluids can also be pumped back up (by changing the valving), so handling the electrolyte will be safer and easier.

 

Another feature of the pumps I'm using is that they're NOT positive displacement pumps, so when they're de-energized, the fluids can drop back down to a lower tank. With a sodium system (where everything stays in solution) this would allow a two tank cell where the larger, lower tank can be a reservoir and an upper tank the reaction chamber (RC) where the electrodes will live. With the pump at a lower position, moving the fluids from the reservoir up to the bottom of the RC and then letting the mother liquor gravity feed from the top of the fluid level in the RC back into the reservoir, the fluid system would be complete.

 

The advantage of this type of setup is that if the power fails, the fluids run out of the RC, and back into the reservoir by gravity, so the unpowered electrodes are not sitting in the electrolyte (where they'd be slowly attacked) as long as the power is off. If the power system is prone to outages in the area where the system is set up, this design would be advantageous.

 

WSM

Edited May 1, 2016 by WSM

[WSM]

I also made progress in toughening the power supply for outdoor use. I placed the copper busses in a piece of thick phenolic/linen board mounted to the edge of my heavy aluminum closure, holding the power supply. The phenolic board also holds the power cord coming into the supply as well as an on/off toggle switch in line with the hot leg of the power cord. Once the power supply outputs are connected to the busses and the perforated metal closures (for ventilation and cooling) cover the other openings, my 5 Volt, 55 Amp DC power supply will be ready to connect to the system with custom made, welding cable, power leads.

 

I'm also arranging a weather resistant power distribution system for my outdoor workbench, which will supply power to the pumps through switched outlets and constant power to the power supply, sensors and controls; as well as an LED lighting system I'm experimenting with (we'll see if it works).

 

I'll show more as this whole setup progresses.

 

WSM

Edited May 2, 2016 by WSM

[Arthur]

When I did commercial electroplating, the LV DC was moved from the rectifier room to the workshop along thick (6" x 1/2" ) copper buss bars assembled into big conductors and lapped at the direction changes.

 

Maybe the PSU could go in a large plastic storage box with a fan pushing air in, with the air outlet down a piece of drain pipe out to the cell. This way you can use a remote fan to clear any smelly fumes from the cell area.

[WSM]

When I did commercial electroplating, the LV DC was moved from the rectifier room to the workshop along thick (6" x 1/2" ) copper buss bars assembled into big conductors and lapped at the direction changes.

Maybe the PSU could go in a large plastic storage box with a fan pushing air in, with the air outlet down a piece of drain pipe out to the cell. This way you can use a remote fan to clear any smelly fumes from the cell area.

 

Hi Arthur,

Those are huge conductors. I imagine either you dealt with very large currents or were trying to cut I²R losses in the LV DC side.

 

My purpose in using busses is to consolidate the multiple PSU outputs (3 each + and -), pass through the insulator board and make a single contact point for the welding cable crimped lug to tie onto with brass hardware. The other end of the welding cable (terminated similarly on the opposite ends) is tied directly to the ends of the electrode leads (also with brass bolts and washers).

 

I like the idea of a plastic enclosure for the power supply, and if the weather doesn't continue to cooperate, I may quickly adopt it. As for the PSU venting doing double duty by forcing the fumes from the workbench, I'll forbear for the moment, but may consider it for later if it appears to be expedient. Edit: Nice idea, though.

 

Thanks for sharing your experience and also for the suggestions.

 

WSM

Edited May 2, 2016 by WSM

[Arthur]

In the chrome plate tank we ran 800A into each hanger, there may have been up to six hangers in at a time -two bike frames or four bike wheels on each hanger.

 

However my point was that with some fat cable once you can save the PSU from destruction by corrosion. I wonder if by blowing clean air with a fan, one could use a venturi made of drain pipe to remove the off gasses from the cell without the spray corroding the fan or the electrode connectors.

[WSM]

In the chrome plate tank we ran 800A into each hanger, there may have been up to six hangers in at a time -two bike frames or four bike wheels on each hanger.

However my point was that with some fat cable once you can save the PSU from destruction by corrosion. I wonder if by blowing clean air with a fan, one could use a venturi made of drain pipe to remove the off gasses from the cell without the spray corroding the fan or the electrode connectors.

 

A nominal five thousand ampere system IS huge. My cables are 2 AWG, which are quite over-sized for the system I'm running, but will allow for an efficient power transfer or later modification (upgrade), if required.

 

I may learn differently, but I hope any salt spray and fumes will be contained or vented passively from my system. I'm using a larger, hard PVC vent tube at the high point of the lid on my RC (which has a soft silicone tubing seal to keep salt creep down), plus using compression fittings on all the top ports in the cell.

 

This is the type of seal used in my larger RC. It seals between the ID of the tank and the OD of the support ring on the lid.

 

If these methods don't work, I'll definitely adapt whatever means are required to keep things working without the self-destructive effects of errant salt spray or fume flow.

 

A good friend and fellow electrochemist, used a large jar plumbed in the path of his exhaust vent to capture any salt spray or water vapor (and return it to the system) and neutralize any chlorine released harmlessly before the exhaust could leave his system. Basically, the only thing to vent out of his system was H₂.

 

If active venting is required, I'm considering a draft system where the computer fan is not in the line of fire. I think it would work well.

 

I can and will take measures to keep my system as safe as possible.

 

Thanks for the suggestions.

 

WSM

Edited May 2, 2016 by WSM

[Arthur]

The problem with Chrome plating is that it maxes out at 8% current efficiency so to put chrome onto anything you use a lot of electricity.

[MadMat]

Arthur, not to mention chrome plating is very intolerant of ripple in the current. The power supplies for chrome plating need to have very large choke coils to filter out any ripple left over from rectifying ac to dc current. I have seen high efficiency chrome plating baths that ran higher in the neighborhood of 20%. They usually employed higher sulfate to chromic acid ratios and also used higher concentrations of fluoride to act as catalysts. As far as corrosion of your power supply, unless you are running a very large cell, there is no problem with having longer wires to keep the power supply away from the cell. Another idea would be to add a small amount of synthetic detergent to the cell, creating a foam layer on the top of the cell solution to keep any mist down (this is also used in chrome plating).

Edited May 3, 2016 by MadMat

[taiwanluthiers]

Has anyone investigated how the detergent will react in a chlorate cell environment, and whether or not electrolysis will break it down forming all sorts of weird compound/contaminant that may do weird things?

 

Not many chemical substance remains intact in a chlorate cell...

[Arthur]

IIRC "Zeromist" a foam layer creating detergent for chrome plating was an unspecified per-fluoro sulphonic acid compound, but like everything else it got eaten by chromic acid and needed regular replenishment.

 

For the purposes of a electrochemical cell IMO a suitable lid would be better

[MadMat]

As I said, it was an idea. It would have to be tested out. Chromic acid (actually chromium trioxide) is a very strong oxidizer. I don't think anything in a (per) chlorate cell would come close to the corrosive properties of a chrome plating bath. That being said, I feel it would be worth a try. Another idea I just thought of; back many years ago, they would simply float a layer of small plastic balls on the surface of the plating bath to keep the mist down. In any case, it might simply be a good idea to physically place the power supply away from the cell and provide ventilation

Edited May 3, 2016 by MadMat

[schroedinger]

MadMat i ca tell you just ends up in a brown mass. A chlorate cell is actually very good at oxidizing everything, any piece of chrome present in your cell will get oxidized into dichromate, if it touches the anode and even with a MMO anode and steel cathode you find some small impurities after some run time, which can't be found at loading the cell.

[OldMarine]

I do work for a plant that makes car wash chems and their mixing tanks all have the plastic beads floating in them to hold down mist and foam. A 1000 gallon tank has about a 3" layer floating on its surface. Edited May 3, 2016 by OldMarine

[WSM]

As far as corrosion of your power supply, unless you are running a very large cell, there is no problem with having longer wires to keep the power supply away from the cell. Another idea would be to add a small amount of synthetic detergent to the cell, creating a foam layer on the top of the cell solution to keep any mist down (this is also used in chrome plating).

 

I'm still deciding whether to use shorter cables and keep the power supply closer to the cell or use longer cables and run the power supply under the table the system is set up on.

 

I'm leery of adding organics or incompatible compounds to the mother liquor. My preference is to add only things that are already found in the cell, so as to not contaminate my cell or final products. If there is a reasonable or logical reason for adding something, I'm willing to consider it, but if the benefits don't heavily outweigh the potential problems, I'm avoiding it.

 

WSM

[WSM]

For the purposes of a electrochemical cell IMO a suitable lid would be better

 

I completely agree !

 

WSM