making potassium (per) chlorate

[Swede]

For your setup, I'd look for a graphite anode, and either a graphite or Ti cathode. Since you are at a fixed voltage, experiment with electrode spacing to achieve about 20 amps. The wider apart the electrodes, the less current that will flow. Use NaCl which will produce NaClO3... all will remain dissolved. The graphite will slowly decompose. At the end of a run, you will have a black slurry. Filter the liquor like crazy, do it two or three times, to get rid of the graphite. Then convert the NaClO3 to KClO3 with saturated KCl. Recrystallize the crude KClO3, and you should end up with some decently pure product.

 

I've blogged extensively on my experiments so far, maybe you'll find some useful info there. Good luck!

 

Edited/Added: I was thinking, rather than buy pre-made Pt-coated anodes, does anyone know how practical it is to electroplate a niobium mesh with Pt using...

 

PLATINIC CHLORIDE, HEXAHYDRATE, 99.9% pure, ACS Reagent, -20 mesh, (Chloroplatinic Acid, Dihydrogen Hexachloroplatinium (IV)), H2PtCl6.6H2O

 

which sells for $70/gram? Does anyone know how much Pt, by weight, is contained on a small perchlorate anode? If five grams of this stuff can electroplate 10 or 15 anodes, it might be possible to roll your own for much less than a commercial anode would cost.

Edited August 24, 2008 by Swede

[tentacles]

Swede: Electroplating platinum on titanium is being experimented on by someone over at science madness, 12AX7 I believe. He has about $400 (as of dec '07) worth of chloroplatinite (Potassium salt I think) something like 15 grams anyway, and he's tried electroplating titanium various ways, without much success at getting it to adhere well. There is definitely some special preparation of the substrate done (think trade secret) to successfully make platinized anodes.

 

I think it might be cheaper to make your own chloroplatinite than it would be to buy the salt, as the salt per g platinum is like $90-150 vs ~$1450/oz (Wow it's gone down a LOT since last winter).

[PyroMedia]

What should i filter with? and can i use a steel anode?

[Mumbles]

A coffee filter should proably do the trick for fine particulates such as small bits of the electrodes that may eventually fall off, or just random sediment. As far as the anode, no idea. I do seem to remember there being a use for some stainless steel, but probably for the cathode. Chlorate is more forgiving, but perchlorate requires some rather exotic anodes for the most part if you want it to last a while.

[Swede]

I think it might be cheaper to make your own chloroplatinite than it would be to buy the salt, as the salt per g platinum is like $90-150 vs ~$1450/oz (Wow it's gone down a LOT since last winter).

 

Thanks for the head's up. If it was a straightforward plating process, I think I'd consider it strongly, but Pt is just too darned expensive unless you know the process will work. I need to look at that thread. I wonder if he's using or tried niobium as a substrate. Ti behaves much like Al electrochemically, and plating aluminum is a bitch because of the oxides that form. Niobium may be easier.

 

PyroMedia, I'm fairly certain double or triple coffee filters will remove the graphite. Don't use steel in any form for the anode... it will simply dissolve. I've tried it! You can use stainless steel as a cathode, though. Graphite would probably work best for an inexpensive setup for both electrodes.

[PyroMedia]

ah, yes i meant stainless, sorry.

[Swede]

ah, yes i meant stainless, sorry.

 

Just to clarify, ANY ferrous metal as an anode (The + connection) will die quickly, and dump troublesome Fe ions into the bath. I tried a test with some 316 stainless tube as an anode, and within an hour it was nearly cut in half.

[PyroMedia]

Thanks for the help, ive been playing around with different anodes So far ive tried:

Aluminum(wasn't very good, it disenagrated quite fast)

Magnesium(was bubbling like crazy, any problems with this that you can see?)

Copper pipe(made my tank look like a giant turd was floating in it, the water turned all brown)

 

And im looking for a good graphite supplier besides pencils

Edited August 25, 2008 by PyroMedia

[Mumbles]

I had always wondered about graphite golf club shafts. The off cuts should be easy to get. I understand they are more of a carbon fiber base, but it might be interesting to try sometime. If only I wasn't aweful at electrochemistry.

[tentacles]

PyroMedia: For graphite you can use gouging rods (peel off the copper jacket, easy to do) from a welding supply shop. You may have to buy a box of 25 or something, but they are pretty cheap. They don't last too great, though, the graphite is fairly low density. EDM graphite (see ebay) will last longer. In the long run, save up the money and buy a MMO anode / Ti cathode set from northstar. The headaches in filtering and other BS it will save you are enormous. Plus they are more efficient than graphite.

[PyroMedia]

i would but they want like 30$ for shipping. and i would ahve to buy 2 sets if i wanted perch too

 

i would happily buy a used one though

Edited August 26, 2008 by PyroMedia

[Arthur]

To get a decent yield start with NaCl because more will dissolve in a volume of water. This means that there will be lower cell resistance and less heating. You really do have to master PbO2 electrodes or buy precious metal electrodes. Which means you have to make a LOT of product for it to be viable. One guy in the UK had 80 amps going into his cell from a welding transformer controlled by a variac. He had massive yields. Like 50kilos! though he did run it for 160 hours a week just a short downtime to clean up.

 

When you have that scale it's worth the effort to crystalise NaClO4 then react with KCl for KClO4 and do the tests for purity.

[PyroMedia]

I have a car battery charger capable of 50 amps but it says dont run it for more than 7 seconds would this change by any chance with electrolysis?

[Swede]

As far as the economics of this whole process, I think we must be honest and say it would be cheaper just to buy the chems, but 1) Where's the fun in that? and 2) In some markets these oxidizers are not available.

 

PyroMedia, some thoughts - the internet is FULL of failed electrodes. Thousands of people have tried everything imaginable, and the choices truly come down to graphite and MMO for chlorates, & Platinized mesh and PbO2 for both chlorates and perchlorates. I'm sure there are others, but they're either not practical, not available, too expensive, etc. Graphite is the cheapest of these by far.

 

The MMO anode from Northstar produces brilliant, clean, snow-white chlorate crystals, zero contamination beyond KCl and maybe some hypochlorites, all easily removed with recrystallization. If you order just the anode, you can make your own cathode from Titanium or stainless, Ti is much better. Another possibility is the electrode set from a saltwater pool chlorinator.

 

As for your battery charger, I'd recommend you limit the current to 25 to 35 with suitably large electrode spacing. This should keep it healthy. It sounds like the 50 amps is for car STARTING, and this is definitely NOT continuous duty. Either way, check the charger for signs of overheating. A small fan blowing air through the case will do wonders. If you can't touch the case because it's too hot, that means IT IS.

 

Conversion of chlorate to perchlorate... Electrochemically is best, but apparently it is possible to convert chemically with a powerful oxidizer. Potassium peroxymonosulfate is available at pool stores as a non-chlorine "shock" and I am tempted to give it a try. It would be a real boon to come up with a chemical chlorate --> perchlorate process that is predictable, inexpensive, and effective. Then we could ignore the expensive platinum anodes! Anyone heard of any success with a chemical oxidation route? O₃? H₂O₂?

[tentacles]

Saltwater chlorination electrodes are hit and miss, at best - It all comes down to what coating was used on the ones you end up with. A fellow on sciencemadness tried a set, but the oxygen (and possibly also chlorine) overpotential isn't right for making chlorate.

[Arthur]

The power supply is very important! Less than 10 amps and production woll be seriously slow, more than this and there will be losses at connections and wire gauges to consider.

 

Foe optimum DC output then an adjustable smps giving up to 12 v at 20 to 50 amps is best, and these will be surplus market or seriously expensive.

 

For basic DC, a Variac feeding a welding transformer feeding some well chosen schotky rectifiers, allows control without excessive circuit losses.

 

The computer PSU as advocated will allow a fair current off the 5 volt rail but 5v though OK for chlorate is not enough for perc production which needs about 7 volts across the electrodes hence may need 9 volts across the PSU terminals to account for cct losses.

 

Getting 160 hrs a week is important to production rates but usually beyond cheap solutions. Do ensure that the PSU is ventilated with clean air or the fumes will eat the cct board and copper wires.

[Swede]

Saltwater chlorination electrodes are hit and miss, at best - It all comes down to what coating was used on the ones you end up with. A fellow on sciencemadness tried a set, but the oxygen (and possibly also chlorine) overpotential isn't right for making chlorate.

 

Ahh crud. In the other chlorate thread, I was postulating on using one of these sets because they come as a tidy, pre-plumbed package that could be tied into a system with circulation. I would have guessed that they contained a pretty basic MMO anode with Ti plate cathodes, and would have made chlorate w/o problem, although not perchlorate.

[Swede]

I think I've made a valuable observation that may help people who are into a bit of production, more than just a batch or two. The following applies to potassium chlorate cells only. I have not experimented with sodium salts at all, and perchlorate is still in the future.

 

The traditional way to reuse old electrolyte, which by definition is saturated with KClO3, and thus contains loads of goodies, is to boil to reduce volume, then make up the remainder with saturated KCl feedstock. Boiling this stuff is one nasty business. It destroyed one stainless steel pot, and all my glassware is one liter or less. Boiling down 8 liters of chlorinated/hypochlrinated electrolyte 1 liter at a time sucks.

 

Faced with that chore again, I rebelled, and simply made the next cell 1/2 old electrolyte, and 1/2 new feedstock. At the end of that run, I now had 1.5 X the cell volume in used electrolyte. With each batch, I had extra, and it was accumulating in a big poly jug. It is like a breeder reactor! It keeps making more "fuel."

 

I decided to try an experiment. Into the poly jug full of used electrolyte, I simply added handfuls of KCl salt, a few kilos. I was curious to see how much KCl the electrolye would take up, being already saturatd with chlorate. Without agitation or boiling, I was counting on time, several days, to allow KCl uptake. This morning I cranked up the cell once more, but before I did, I tested the chloride content of the poly jug full of old electrolyte + KCl salt. I was a bit amazed to discover that the salted, recycled stock was close to my pure feedstock in chloride concentration. I didn't even have to filter, I simply decanted right into the cell.

 

Thus the new cell STARTS with both saturated KClO3, AND an adequate chloride supply. Mutual solubilities can be tricky. A lot of internet searching revealed at best some tabulated data that will take some effort to understand, but it seems that the presence of KClO3 in the used electrolyte did not overly inhibit the uptake of the fresh KCl, and the process produces a satisfactory electrolyte without boiling. Further benefits - the chemistry, the pre-existing aqueous products of the used electrolyte, give the entire process a head start once current is applied to the recharged cell.

 

Conclusion: Prepare a "recycle" jug by layering the jug inches deep with KCl. Dump your hot, used electrolyte into this jug, and allow several days, with occasional agitation, for the fresh KCl salt to dissolve to mutual saturation. No more boiling, AND you get the benefit of almost immediate crystal formation because the recycled electrolyte is saturated with chlorate.

[tentacles]

Nice! This is along the lines I suggested a while back, in some thread or other. No need to toss out or boil old electrolyte. Less work = more perc.

[Swede]

I found a very complete guide to chemical compatibilities of various chemicals vs. the typical plastics one would use to make a cell. This doesn't stop an experimenter from doing a run or two with certain materials, but I've come to a bit of grief recently as certain materials have failed dramatically, literally falling apart and dumping hydrogen and chlorine into my shop, which is dangerous and nasty.

 

The 2 products we need to be concerned with are:

1) Aqueous (dissolved) Chlorine, and modest gaseous chlorine - this is the nasty one

2) Hypochlorites; or bleach

 

All other products are reasonably benign.

 

Some typical plastics used in cells and fittings. I've tried most of them, and my observations agree with this data.

PVC - polyvinyl chloride

HDPE - high density polyethylene

PC - Polycarbonate - "Lexan" etc

PP - PolyPropylene

Epoxy

Nylon

PTFE - Teflon

PVDF - Kynar

Silicone

 

 

The grading system, ND = no data, A=no effect, B=minor effect, C=moderate effect, D=Don't bother

 

The first grade is for Bleach. The second, for aqueous chlorine.

 

PVC - A A

HDPE - A C

PC - A nd

PP - D D

Epoxy D D

Nylon A D

PTFE - A A

PVDF - A B

Silicone nd D

 

I can vouch for the fact that nylon fittings are worthless, and unfortunately, 98% of what you buy at a hardware store are nylon. PTFE rules, but is cost prohibitive. The hopeful HDPE bucket-cell may have problems with the chlorine. PVC looks strong, as does PVDF, or "Kynar" which are available as cost-effective tubing and bulkhead fittings. One final plastic not listed is PET, polyethylene terepthalate, or coke bottle plastic. PET gets strong marks for chlorate use, and can be purchased in dense bars, or you can use a coke bottle as a cell, with some imaginative work. Epoxy - sucks, and self-destructs, quickly.

 

The reason PVC appeals to me is the workability. Cuts well, solvent welds, and reasonably priced in sheets, rod stock, and as the ubiquitous fittings from any hardware store. The main problem is temperature, it must be kept at 60 celcius or less, preferably 45 or less, for logevity.

 

Hope this helps, it may save someone some of the trouble I've been through, watching materials self-destruct under the influence of chlorine and hypochlorites.

[WarezWally]

http://www.coleparmer.com/techinfo/ChemComp.asp

[Arthur]

From what I have read ( here and UKPS and Sci Madness and the Cape Canaveral site ) only lead dioxide will go straight through from chloride to perchlorate, and that seems to be a challenge to make.

 

What is the feeling here about using economy electrodes to make sodium chlorate then at say 12% chloride letting the less soluble chlorate ppt out and collect it, wash the chloride out, return the liquor to the cell and the crystals to a perc cell with pt electrodes. Would this avoid the erosion zone at low chloride concentrations where carbon and platinum both erode to destruction.

 

I was thinking of a cell making about 5 kilos a week. it has to be enough to allow for the cost of the electricity and the testing costs so that I can have some certainty that the residual chlorate and chloride is in acceptable limits (ppm ?)

[Swede]

Hi Arthur, what you are proposing is exactly what I'm doing. I don't know if you've read my blog here at APC. I'm starting with potassium salt rather than sodium, and by definition the potassium salt will ppt out during chlorate production. With a good MMO anode, my tests have shown that the KClO3 salt is quite pure and ready to go into a perchlorate cell without recrystallization.

 

The drawback to this process is the relatively low solubility of KClO3. This can be made up for by sheer cell volume. The benefit is a much cleaner product. You can almost consider KClO4 to be insoluble relative to KClO3. When the perchlorate precips out, it is going to be good stuff. A stiff washing should remove most clinging chlorate solution, but for pyrotechnic purposes, post-processing/recrystallization and destruction of remaining chlorate will be needed.

 

My own experience has shown that good KCl feedstock will start at about 125 g/l chloride ion. I have been stopping chlorate production at 80 g/l chloride, which is conservative so as to go easy on the MMO anode. Yields have been about 150 to 200 grams per liter chlorate, and this jibes with the chloride numbers. If you want 5,000 grams per week, you'll need amps as well as feedstock volume. 160 amp hours are needed for 122 grams of chlorate (at 100% efficiency; count on 40 to 60%) let alone perchlorate. I'll let you do the math, but I'm guessing you'll need 150 to 200 amps to reach 5 kilos/week. All my experience so far has been chlorate. I'm learning as I go, and perchlorate will start soon.

 

As for the anode, again after reading til my head hurt, PbO2 anodes are possible, but they'll take massive screwing around. I plan on some experiments later, but for now, I'm using Pt. Northstar Pyro sells Pt over Niobium, $80 or so. I've found a slightly larger Pt over Ti for much less... I need to try it and see if it'll hack it.

 

I'd love to get some feedback on my blog idea for a super-cell. I feel like I'm talking to myself with the exception of a couple people. After endless hours of internet search, I found a guy who sells short sections of huge PVC pipe, up to 24" dia. A 12" PVC pipe has a volume of 1.66 liters/inch, so a 12" section, butt solvent-welded to a piece of sheet PVC, will create a 20 liter tank; all you have to do is make a lid for it. Anyway, his website: http://www.shortpileplastics.com/ Guy's name is Brian, and he's easy to work with.

[Arthur]

The major drawback with using KCl is the low solubility. At below 10% chloride carbon AND platinum electrodes erode rapidly. Using sodium chlorice you can electrolise the solution down from about 40% Cl- to 10%Cl- so there is a lot of product. Using KCl you can only start at about 16% and go down to 10% that's a low conversion rate to start with.

 

I was planning to electrolyse with carbon electrodes to 10% chloride then do a simple purification, then drop everything into the perc cell for the last stage. That way the transition through the corrosion zone of low chloride is passed by crystalisation rather than electrolysis.

 

In the UK KCl is not cheap so starting with "Lo-salt" may be necessary.

 

IMO home production of ClO4 may be essential as the US agencies tighten up and the European market loses the Polish suppliers to transport rules

[Swede]

I hear what you're saying, and there was some question in this thread if the so-called 10% rule refers to 10% by weight Cl- ion, or 10% of "what you start with." I have a hard time imagining a decent anode eroding badly when you go from 15% to 9%... In terms of what the anode "sees", 10% is not all that different from 15%, whereas if you go from 15% to 1.5%, then yes I can see an anode struggling.

 

I can't think of any way to check the anode other than visually. I don't have a balance capable of seeing a miniscule erosion, so I stick it under a microscope, and also look for dark solids, and the only dark solids I've seen are plastic fragments at 7% Cl-.

 

I personally think it is much easier to start with a very large cell volume, rather than messing with metathesis reactions. But however you make the chlorate, I agree that starting a perc cell with relatively pure KClO3 is a good way to go.

 

In the UK KCl is not cheap so starting with "Lo-salt" may be necessary.

Is "Muriate of Potash" available at garden stores? That's a relatively cheap source, much cheaper than table salt substitutes. In the U.S. we buy 50 pound sacks for water softening systems for $14 or so. Are either of these sources possible?

 

IMO home production of ClO4 may be essential as the US agencies tighten up and the European market loses the Polish suppliers to transport rules

This is inevitable. I think it will happen in the U.S. and Europe sooner rather than later. May as well get a head start on it.