making potassium (per) chlorate

[Swede]

I meant to add, I'll do a qualitative check for perchlorate presence in the salts gathered from the batch where I took the Cl- to its lowest point, which is probably 7%. If the anode was struggling at this concentration, I'm guessing there would be identifiable perchlorate ions in the solution. Might be worth a look-see.

[Mumbles]

I would think that 10% is 10% solution. However is this 10% w/v chloride, or 10% w/v NaCl? A concentrated NaCl soln only starts out at 22% chloride w/v.

[tentacles]

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 ?)

 

I think you're wrong here, dann over at sciencemadness has shown (and the papers also show) that any anode that can make perchlorate can go from chloride > perchlorate, it's just a question of how badly they will erode. dann even showed a successful magnetite perchlorate cell - it does require pH control to make chlorate, but when it was making perchlorate he didn't have to add (any? as much?) HCl.

 

The feeling here, is that this is simply the only way to go unless you want to piss away anodes. Even PbO2 erodes considerably when going from chloride to perchlorate, and it isn't all that efficient at making chlorate. So - why waste your time using PbO2 to inefficiently make chlorate, just use another type of anode to do that part. I believe dann is/will be (soon, I hope) testing his PbO2 anode going from pure chlorate > perchlorate.

 

Since I have the chemicals to make both MnO2/Co3O4 and PbO2 anodes, I hope to be self sufficient.

 

I did speak to a fellow in the UK who was using, very successfully, massive PbO2 anodes to make gobs of perch. He just pumped like 80A into the cell and harvested/resaturated once a week, I believe. I don't remember if he was using NaCl or KCl.

 

Have you actually called farm stores, feed stores and fertilizer centers? I find it unfathomable that you can't locate a bag of the potassium fertilizer that is 97% of the world's potassium fertilizer. I doubt you'd find it at any sort of 'consumer' sort of establishment, you need to talk to a farm supply, better yet might be a feed store, as they are the sort of place used to selling 1 bag quantities.

[Arthur]

The whole point of the two tank, two cell system is to economise on electrodes. Platinum is expensive here! And it erodes badly in low chloride cells. Graphite is cheaper but disintegrates and contaminates the product.

[Swede]

This is a good discussion. There is more than one way to skin this cat, and for me, volume is the key. I can live with the low solubility of potassium chlorate by simply making jumbo perch cells. Nothing goes to waste, leftovers in the liquor from the perch cell, especially with a Pt anode, should be clean (but dilute) potassium chlorate, and a tiny bit of perchlorate. Boil this down or use as-is by refortifying with fresh K-chlorate salt. The only anode I've used for chlorate is an MMO anode, and I'm sold on it, the potassium chlorate it produces is exceptionally clean. A good test (but it might result in the loss of an MMO anode) would be to drive one to near destruction, and note the chloride level where things go bad. Add a couple % for future runs.

 

One thing I'd planned on doing, and may still do, is take my stack of notes and (in a constant current setup) plot voltage as a function of chloride ion concentration. Interestingly, I've noted that the voltage curve is shaped like a saucer; it starts high, dips, then begins to rise again. That may be one way to identify when the system is struggling, and it's time to stop chlorate production.

 

Man I'd love a big budget to research this stuff. But commercial anodes are expensive, and no one wants to hurt one. Arthur, Pt is expensive everywhere! I agree with your premise, I think it is easier and cleaner to do a two-step perchlorate process.

[Arthur]

My reason for the two cell system is to economise on electrodes! Carbon rods are really cheap for making chlorate from a chloride solution, but will destroy themselves before perc is formed. Pt will make chlorate from chloride til there is about 10% chloride left the the electrode dies. Pt will make perc from chlorate til there is a %age of chlorate left. So whatever process the product will need purifying past the electrolytic limit. Every drop of surplus can be fed back into the system. Chloride from the chlorate can go back into the first cell, chlorate from the perc can go back into the second cell.

 

This way you only need Pt electrodes for one job in the perc cell. You can use MMO or carbon in the chlorate cell for a LOT less money!

 

Is anyone wise enougn to design the spot tests and quantitative analysis for the process. Ion selective electrodes, rows of burettes or.....

[Swede]

Pt will make chlorate from chloride til there is about 10% chloride left the the electrode dies

 

Arthur, I don't believe this is true, unless by "death of the anode" you mean SOME erosion... Of course there is erosion from the moment the cell starts, we just want to keep it reasonable. After some very hard running down to 7% chloride, my MMO anode looks as good as it did right out of the plastic bag it came in. And Pt is better than MMO.

 

I think we are in agreement on just about every other point. I like a predictable, clean process.

 

Ion-selective electrodes would be killer. I need to dig through my big Cole-Palmer catalogue and see if they, or any other source, has them, and how they might be utilized.

 

OK guys, this is really weird... my perchlorate cell was started two hours ago, and it seems to be going well, but I caught a whiff of the evolved gasses from the cell, and there is the unmistakeable odor of OZONE! WTF? I don't remember reading of O3 evolution from these things. This is odd and potentially a monkey wrench in terms of materials. Ozone is nasty. Anyone else encounter this?

[tentacles]

Ozone is a possibility, but it shouldn't really be evolving. It could simply be one of those things that happens with platinum anodes. Are you sure it isn't just a strong oxidizer smell? If the pH is low it could be (per)chloric acid, which I imagine smells like any strong oxidizing acid / ozone. (obviously, this would be worse than ozone) I know it is possible to produce ozone through electrolysis with platinum anodes. I suggest posting on science madness about this.

 

I have a question, though, you mention adjusting the pH of your chlorate cells with the top up water/electrolyte, are you using a pH meter to test the pH, or are there strips or tests that hold up?

[Swede]

Tentacles, I need to check the pH of the perc cell. I had been using pH paper when working with chlorate by first boiling the sample to help eliminate some of the hypochlorite. Even when it was not quite all gone, you'd get a flash of color before the bleaching that would give a decent clue as to the pH.

 

The top-off was simply 5% HCl and 95% KCl from a wash bottle. My pH control has been rough, at least until I can replace the pH electrode for my meter that took a dump. The chlorate cell seemed to want to stabilize at 8.0 or so, and it did require additions of acid to get it below 7.0 The air bubbler/mixer helped quite a bit by keeping evolved Cl2 gasses in contact with the electrolyte for a much longer period of time.

 

I'm pretty sure it's eolving ozone. The good news, though, is after that initial mild panic, the cell began to drop perchlorate steadily, and there's probably 1/4" at the bottom after just a few hours. It looks like it's going well.

[Arthur]

If I start a perc celll system, it will run for months so I don't want to erode platinum if I can help it, I certainly don't want to enter a region of high erosion.

 

Currently my partly developed plan is to get a small ( 5 - 10 litre ) glass vessel and electrodes for chlorate. probably use a redundant computer PSU for this, with carbon and ?? electrodes. This should make and precipitate sodium chlorate which can be removed by glass syphon tube. The cell being topped up with salt, water and returned filter liquor.

 

Syphoned precipitate being filtered (GFA circles?) and gently washed - washings back to the chlorate cell. The crystals should then be a very low chloride sodium chlorate ready for a similar electrolysis setup with higher voltage and expensive electrodes in a minimum erosion setup. The Perc cell running with precious electrodes and a saturated chlorate solution should produce perc as a PPT and keep using a saturated, low chloride, chlorate feedstock. Again a glass syphon tube should enable the ppt/crystals to be picked out and filtered, and the liquor returned.

 

The final product then is a crystaline mass needing freeing from chlorate first by recrystalisation and secondly by chemical destruction of chlorate. This should be adequately pure sodium perchlorate and just need reprecipating from KCl to give Potassium Perchlorate.

 

Now I need to sort out the process control regime to make sure that what I really want does happen and nothing else. Also to prove that the product K perc or Na Perc has the desired purity.

 

With the investment in electrodes etc there is little point in only producing grammes or perc! Also If I make perc I need to destroy residual chlorate and test for purity, so the test regime is significant. Perhaps If I can electrolyse for a week with daily pH checks then I can take chlorate off at the weekend and refil the chlorate cell and set up the perc cell.

 

Platinum erosion is significant on a cost basis! The value of a kilo of perc doesn't allow you to lose much platinum. Even losing a milligram or two per kilo of perc would change the cost a LOT and with platinum plated electrodes causing pitting of the platinym would kill the whole electrods as the substrate failed

Edited September 6, 2008 by Arthur

[Swede]

Hi Arthur! I like your methodical thought processes, and the need to ultimately be economical. How are you going to gather Sodium Chlorate crystals, given that it's solubility is superior to that of the feedstock, NaCl?

 

Some solubilities which I have found very helpful...

 

Salt--------0 deg-----100 deg

 

KCL--------238-------567

KClO3------71--------570

KClO4------8----------218

 

NaCl--------357-------391

NaClO3-----790------2300

NaClO4-----2090-----2840

 

With sodium, the solubilities INCREASE as you progress - with potassium, they decrease. If you start with sodium salt, there wil be no crystal formation... the chloride ion concentration will drop, and the sodium chlorate will remain in solution. The only way to know when you are finished with a chlorate run is to measure chloride ion. Near the end, you will have a partially saturated NaClO3 solution, depleted chloride, and no crystals. If you can get more chloride into the liquor without altering the volume, that would help, but since NaCl is less soluble than NaClO3, how are you going to get only NaClO3 to form and not NaCl?

 

If the anode has deteriorated, as with graphite, then those solids will need to be filtered.

Edited September 6, 2008 by Swede

[Arthur]

I see projects dumping thousands of £/$ into making a few grammes that might only be chlorate! I don't want to go there. Careful planning will get me to a trial plant of a litre or so then possibly I can scale it up to ten litres. I'm studying the Mutual solubility graphs on the Cape canaveral site. I think there is a way!

[Swede]

My first perc batch turned out better than I thought. The crystals (as I mentioned in my blog) were much finer than the beautiful chlorate crystals, which made processing a bit of a pain.

 

http://www.5bears.com/perc/pcrop03.jpg

 

It's nice to work two filters simultaneously; it speeds things up. The crystals were washed first with ice water, then with ethanol. I have taken to using ethanol as a final wash for many of my crystal batches, as it wets better and ultimately strips clinging aqueous contaminants in an effective manner. Huge bonus - dries much faster. I'd use methanol, but denatured ethanol is cheaper.

 

http://www.5bears.com/perc/pcrop04a.jpg

 

Mmmm, mashed taters, anybody?

 

With a forced air draft, these crystals were dried in a day, and interestingly, they have the exact texture of commercial perchlorate, a bit clumpy but generally fine and free-flowing. Of course there is serious chlorate contamination, and they need to be recrystallized and purified, and that is my next hurdle in my perchlorate adventure. I have both phenylanthranilic acid and indigo carmine to verify the purity of this product, once cleaned up.

 

More interesting are some microphotographs of a cheap, but apparently very effective Pt over Ti anode I bought. The only anode that I am aware of that is marketed directly to pyro enthusiasts is the Northstar Pyro Pt over Niobium anode. It's expensive, but if it does its job like Northstar's MMO anode, I expect awesome results. Still, cheaper = better, and I went in search of a replacement.

 

The anode I found is marketed to electroplaters. It is Pt over Ti mesh, not Nb. I don't know the thickness. It is MUCH cheaper than Northstar's product. Will it have what it takes to make perc? So far, very good.

 

I put the anode under my Meiji microscope, and took some pics. I love microphotography, but I'm not good at it. Believe it or not, these pics are made with a Sony digital camera held up to the eyepiece of the microscope, not with a camera adaptor. They sell digital eyepiece cameras, but I haven't pulled the trigger on one yet.

 

The anode "water line" was centered under the lense. To the left is anode surface used in my perc batch, while to the right is anode that was above the surface. There is no difference.

 

http://www.5bears.com/perc/anode01.jpg

 

A bit closer:

 

http://www.5bears.com/perc/anode02.jpg

 

Closest yet, revealing what appears to be a coarse texture, which contributes to the surface area of the anode. No discernable wear whatsoever. This anode may be a winner. I'll try to compare it in some fashion to the Northstar anode, but I'm not quite sure how to do that.

 

http://www.5bears.com/perc/anode06.jpg

 

The Meiji stereo microscope has been an important addition to my lab from day 1. The optics are excellent, much superior to a cheap Chinese knockoff, and second only to the incredibly expesive Zeiss microscopes, which are out of reach to all except professionals.

[Arthur]

Has anyone used the economy pH meters from China (typ ebay 270272861402 ) for process control in a chlorate cell?

 

If I make a cell then I don't want to have to buy a multi thousand pound meter for a few rough pH checks. especially as this may not be a lifetime's research project!

Edited September 9, 2008 by Arthur

[Mumbles]

For the price you can't go wrong. Even if it's not as accurate as it says, it's probably good enough for rough control.

[tentacles]

The way I see it, if you're going to buy a cheapshit meter, just get a pH controller. It can serve as a meter as well, and it has the ability to control the pH quite precisely when combined with a pump/solenoid/device. They're about a hundred bucks for a cheap new one. I'm probably going to pull the trigger on one soon. Plus, you can actually put a new probe on them rather than just toss em out after a year.

 

These look all right if the guy offers a 110V model. I put in a question to that effect. There are some "milwaukee" branded ones for $108 that ship from the US but are .1 resolution / .2 accuracy. Who knows how accurate these .01 resolution ones are but the finer resolution could be nice.

http://cgi.ebay.ca/DIGITAL-PH-CONTROLLER-E...1QQcmdZViewItem

Edited September 9, 2008 by tentacles

[Arthur]

Ok can I get one of those pH meters/comtrollers to run as a chloride ion or a chlorate ion or a perc ion measuring instrument.

 

A chlorate cell fully automated, and a perc cell fully automated

 

Current thoughts are a litre test cell then use the same electrics and electrodes in a 30 - 50 litre tank. There should be enough product to be worth all the messing around. I really cannot see spending hundreds on kit to produce a hundred grammes!

 

Keeping the chloride ion conc up in the chlorate cell should economise on electrodes, likewise keeping the chlorate ion up should reduce erosion of the platinum electrode. Some simple control should keep the pH within say 0.5 or 1.0 and keep the efficiency up. Now do I plan to run off night time cheap electricity

Edited September 9, 2008 by Arthur

[gods knight]

Sorry but this may be a little of topic but would it be a good idea to make a chlorate cell for my chemestry project?.

Ive been taking a look at the ideas the other kids are having and can you believe it; typicall volcano ideas agian!!!!!

thats pretty sad for an honors class.

This is why ive decided to make the cell, as I would easily get a "A" compared to my classmates volcano.

I wont need to make it work in the class room but just a presontation on the cell itself.(so no toxic fumes)

 

For future refrence: im in the 10th grade.

Edited September 9, 2008 by gods knight

[Arthur]

Well the cell itself is just a jar with two electrodes and a DC psu. The Knowledge is the research into the anode and cathode reactions - with sources and reading list. The practical is getting it to work on a pilot scale -say 200ml. No school/college is going to give you a Pt electrode to destroy so there is a restriction. The proof is the testing of the product. Make the cell then run it for a while estimate the current efficiency from some day's analysis. Write it all up.

 

Buying the electrodes and the salt and putting it in a beaker is a fail grade. Understanding it all the theory and the practical could get you an A

[Mumbles]

I think you over estimate the US. I could have thrown two paper clips attached to a battery into a beaker of salt water, called it an electrolytic cell, and easily would have gotten an A. They want everyone to pass, and get good grades, and get into college, and everyone is special and happy. Now, I never did this. I'm never happy with a preformance, unless I feel satisfied I understand it with great depth.

 

I think a chlorate cell would be a great idea. It's not very common, and would probably earn brownie/bonus points for a real chemical interest. Seeing as how it is chlorate, and not perchlorate, you don't have to destroy a Pt electrode. Graphite electrodes are pretty cheap and easy to come by. If you really want to impress them, "prove" that it works by adding a few drops of sulfuric acid into a mixture of chlorate and sugar. The chlorate doesn't actually have to come from your cell, but it would be a great finale.

[tentacles]

Keeping the chloride ion conc up in the chlorate cell should economise on electrodes, likewise keeping the chlorate ion up should reduce erosion of the platinum electrode. Some simple control should keep the pH within say 0.5 or 1.0 and keep the efficiency up. Now do I plan to run off night time cheap electricity

 

I've done a bit of reading up on platinum electrode erosion, I posted my findings on science madness (possibly in the platinum anode thread, but maybe not). You don't want to know the numbers. It's like 12AX7 said, if you reprocess your "crud" (eroded anode material) then it's not bad. But the erosion is significant, even in the commercial type cells I was able to find some data on.

 

Here's the quote from my post over there:

"The wear rates are both interesting, and alarming. The lowest wear rate was 5.3 g/ton of Na chlorate, and the highest (discounting the invalid data) 8.6g/t. At today's prices ($72/gram!) that's $381 per ton of perc, *if* we could replicate the lowest wear rate. I don't know if the chlorate to perc wear rates would be lower, but I would expect that as amateurs, we can expect higher wear rates with our less controlled cells.

 

At 8.6g/t the wear rate comes up to $619/ton, which is actually $.3096/lb of perc. Not terrible, really, but probably the biggest running cost besides the time."

 

Commercial producers either reprocess their own crud, or sell it back to those who replate their anodes.

[Arthur]

Now that is a very good reason for being rather carefull with processs control! Also possibly a good reason to use cheap carbon? electrodes for the chlorate step, then Pt only for the perc step.

 

Is anyone able to offer advice on ion selective electrodes for Cl- ClO3- and ClO4- or a wet method fro the analysis of a mixture.

[pkhow]

Does anyone have experience or advice on destroying the residual chlorate in my perchlorate from a K perch cell if the material is now mostly KCLO4. Have you been able to clean it so that the Indigo Carmine test shows virtually no Chlorate by re-crystallizing and rinsing in cold water alone even several times or have you had to use chemical means as well to destroy any remaining Chlorate.. The geocities.com lists materials such as sodium metabisuphite, ferrous sulphate and acids such as HCL for sodium Perchlorate so I am wondering if this is also usable with KCLO4

[Mumbles]

They should still work, though you'll probably have to heat the solution to get enough dissolved for it to be effective.

 

I don't have the time right at this moment, but I will go and take a look at the methods before issuing any final verdict. If they work for sodium perchlorate, they should work for potassium perchlorate with the caveat that some heat my be necessary to dissolve everything.

[Swede]

Is anyone able to offer advice on ion selective electrodes for Cl- ClO3- and ClO4- or a wet method fro the analysis of a mixture.

 

Arthur, just a quick glance through my fat Cole-Palmer catalogue shows that there are some ion-selective electrodes... I see chloride and perchlorate, not chlorate. Some big problems:

 

1) They are very expensive, starting at around $240, right on up to $600.

 

2) Very doubtful that they can be used for continual monitoring, although I am not sure on that

 

3) The perchlorate electrode lists chlorate as an interference ion, meaning the electrode cannot tell the difference, or the measurement will be skewed.

 

4) The range may not be adequate, although the perchlorate electrode does go to 1.0M or 9.8%, not too bad. The chloride electrode goes up to 35,000 ppm, or a 3.5% solution... too low.