making potassium (per) chlorate

[pdfbq]

Today did some testing on thermal decomposition of KClO₃ -> KClO₄

 

I started with 5 grams of KClO₃ and put it in my oven. Heated it to about 380C

Every hour I took a look. The KClO₃ did melt but after 3 hours it still was mostly molten KClO₃

 

The next day I heated things up again and put commercially KClO₄ next to the sample of yesterday and a new KClO₃ sample to the right of the KClO₄

Another two hours of heating did not change much. The samples bubbled a bit, I guess oxigen, but thats was all.

 

 

The methylene blue test indicates I have at least some KClO₄ but the overall result is disappointing I believe.

My wild guess is that it's not so easy to make potassium perchlorate by thermal decomposition.

Edited March 14, 2010 by pdfbq

[Bonny]

Today did some testing on thermal decomposition of KClO₃ -> KClO₄

 

I started with 5 grams of KClO₃ and put it in my oven. Heated it to about 380C

Every hour I took a look. The KClO₃ did melt but after 3 hours it still was mostly molten KClO₃

 

The next day I heated things up again and put commercially KClO₄ next to the sample of yesterday and a new KClO₃ sample to the right of the KClO₄

Another two hours of heating did not change much. The samples bubbled a bit, I guess oxigen, but thats was all.

 

 

The methylene blue test indicates I have at least some KClO₄ but the overall result is disappointing I believe.

My wild guess is that it's not so easy to make potassium perchlorate by thermal decomposition.

 

There seems to be very little information to be found for that prodedure. Do you think your temp might be a bit too high?

KClO3 melts at 356C (Wikipedia) 368C (Mallinckrodt Baker) and decomposes at 400C. I (think) I remember reading that you need to heat so it melts and then just keep it melted for 6 hrs+. I could be mistaken as it was awhile ago that I read this and can't find the source.

 

But, if you have the oven and time, keeep the experimenting going...and hopefully you can perfect it and provide another viable method.

 

EDIT:

On another note, I'm ready to start up my perc cell for another run. I have 1.8kg of chlorate dissolved and ready. I'm just waiting for the water to cool down so I can power it up.

Edited March 16, 2010 by Bonny

[50AE]

I need help guys.

 

Something's wrong with my cell. It seems the electrolyte has lost its conductivity or something. Everything else works OK - the ameter, the power supply. But when I insert the electrodes in the cell, there's no current. If I short the titanium strips of the electrodes, the ameter reads a high value and the PSU turns off, this is normal. But there is no current flowing through the electrolyte. How is this possible?

[ausfire]

I need help guys.

 

Something's wrong with my cell. It seems the electrolyte has lost its conductivity or something. Everything else works OK - the ameter, the power supply. But when I insert the electrodes in the cell, there's no current. If I short the titanium strips of the electrodes, the ameter reads a high value and the PSU turns off, this is normal. But there is no current flowing through the electrolyte. How is this possible?

 

50AE,

 

Is it possible that when you insert the electrodes into the cell essentially shorting the PSU like when you touch the Ti straps? I mean it's probably unlikely unless your electrodes are spaced ridiculously close.

[50AE]

50AE,

 

Is it possible that when you insert the electrodes into the cell essentially shorting the PSU like when you touch the Ti straps? I mean it's probably unlikely unless your electrodes are spaced ridiculously close.

 

No, it isn't possible, my electrodes are far and the PSU is still working, the ammeter shows 0 value.

Also, I'm sure that there is current flowing through them, because I already tried shorting them directly and the amps rised up like they should.

 

Edit: Something is very wrong. I just measured the pH and it was 8.8. I dropped some HCl and what - No chlorine gas came up from the cell!

There is potassium chlorate and chloride on the bottom of the cell crystallized from the cold, though the temperature is better now, it has to be a good solution.

Edited March 17, 2010 by 50AE

[pdfbq]

Also, I'm sure that there is current flowing through them, because I already tried shorting them directly and the amps rised up like they should.

Euhh.. Do you have your anode connected to the + ? (I know, silly question buy these things happen )

I destroyed a MMO anode once, that gave about the same result as you have now.

Test for just 1 sec or so with a nail or some graphite or some else conducting material instead of you MMO anode. You should see bubbles instantly if you have a problem with you anode.

 

edit: some minor

Edited March 17, 2010 by pdfbq

[50AE]

I am FULLY sure that the polarities are OK. I checked it with a voltmeter, and an LED.

[Bonny]

I am FULLY sure that the polarities are OK. I checked it with a voltmeter, and an LED.

 

Did you try as pdfbq suggested using a nail or graphite? It should at least prove that the supply is OK. Are both of your electrodes clean? Maybe enough crap built up on either one to stop current flow...

[50AE]

Today I did:

-change the electrolyte

-test the power supply

-test the cathode

-test the anode

 

And what a suprise - the anode (MMO) doesn't work. There is current flowing through it ( I tried shorting the electrodes by touching them ), but no current from the MMO to the electrolyte. I remember I washed it, but I'll do it again. There's no apparent crap on it.

[Bonny]

Today I did:

-change the electrolyte

-test the power supply

-test the cathode

-test the anode

 

And what a suprise - the anode (MMO) doesn't work. There is current flowing through it ( I tried shorting the electrodes by touching them ), but no current from the MMO to the electrolyte. I remember I washed it, but I'll do it again. There's no apparent crap on it.

 

That's an anode from Swede isn't it? I've had nothing but sucess with mine....I made 15-20kg of chlorate and it still looks new.

Does the anode still look good? Maybe the chloride conc. was run so low it eroded the anode?

 

Otherwise no idea...

[pdfbq]

There is current flowing through it ( I tried shorting the electrodes by touching them ), but no current from the MMO to the electrolyte.

If you use plain titanium as anode you will have exactly the same result. It acts as a diode in (salt) water.

 

I'm not sure you destroyed your anode especially if it still looks OK (does it looks OK when its dry?) but I can tell you how I did destroy mine, maybe that helps...

 

I had a NaCl cell running (not KCl) and miscalculated the runtime. It was more efficient than I thought it was.

I topped it up with water all the time. That day it was running at 8amp and i topped it with about 5% of water. In one hour the amp dropped from 8 to 3! I then stopped the cell. I think the cell came under a critical NaCl percentage. Later I tested with Methylene Blue and it showed positive on perchlorate which means I think 10% or less NaCl was left. I now believe I had only 4% or 3% NaCl left in the cell.

[50AE]

The anode is titanium mesh coated with MMO and it looks like new. It's not working though.

My chloride levels were never low.

Edited March 19, 2010 by 50AE

[bikemaster]

What is the voltage in your cell???

[50AE]

What is the voltage in your cell???

 

5 volts

[bikemaster]

Ok, the problem don't come for to high voltage...

Did you check the connection? I got a problem similar to this, and it was just because the cooper connection was all rust. (Does it work with an other anode?)

[Bonny]

The good news is just harvested another batch of perc, (hopefully) 1kg or more. The bad news is that it looks like my Pt anode took some abuse this time. The outer edge is eroded on both sides, but is actually worse on the side opposite the cathode. I think I might get 1 more run, maybe 2 and the anode wil be toast .

 

Here's the breakdown:

Started with 1.8kg of KClO3 (washed,dissolved/filtered/recrystallized,washed again). 100g/l in an 18l cell. The cell started at 10A and was down to just under 8A when I shut it down. I ran the cell for 87hrs at an average of ~9A, so 783 ah. IIRC correctly, in a perfect world, ~50ah/100g of chlorate @100% efficiency. So 900ah would be required to convert all of the chlorate in my cell. I am assuming my efficiency is more likely <50% and I'm sure I will lose a fair amount in further processing. The material has been washed in ice water, and I use a 200mesh screen- so some loss there. After it dries, I will dissolve/filter/recystallize, and wash again losing some more product.

Anyway, I'll get another batch going in the next few days and hope the anode can still make me more perc.

I'll also hopefully be starting some clean up soon too.

Edited March 20, 2010 by Bonny

[Arthur]

50AE something is clearly wrong with your system, no-one else seems to get such electrode consumption as you do.

 

Do you use tap or purified water? Does your "chloride" contain additives? What temperature does your cell run at?

[Swede]

50AE, your reports are bumming me!

 

All I can think of is that since you are using a modofied PC power supply, there may be something in there (electronics monitoring; smart electronics) that is saying "Something is off with this load - I am shutting down."

 

Do you have a 6V lead-acid battery? Try that, after ensuring the battery is fully charged.

 

Next, try abrading the Ti cathode with steel wool or an aggressive abrasive pad. Don't be shy, get right down to shiny, bare metal. You may have formed an oxide skin on there so thick that conductivity is being hindered very badly. You may have extremely hard water that might be depositing calcium.

 

Next - Gently clean the MMO in hot water. If you have HCl, create a small container (one of those plastic shoe boxes works well) and mix up a 50/50 mixture of HCl and water. Pickle the anode for about 15 minutes. It shouldn't hurt it. I clean mine with concentrated HCl for upwards of an hour with no ill effect. Rinse thoroughly, dry, then wipe gently with some acetone on a rag.

 

Do you have an ohmmeter? Any cheap one will do. Touch the black MMO (not any bare Ti spots) on the mesh on one end with a probe. Then touch the other probe to a distant MMO spot. It should read only a few ohms, 3 to 10. If it reads into the kilohm range, there's some sort of coating built up.

 

That is all I can think of. My gut says it's the power supply despite your touch tests. When things like a cell begin to fail, it doesn't go to zero, the amps (at a given voltage) begin to slowly drop, but there should always be some current showing.

Edited March 21, 2010 by Swede

[50AE]

Guys, seriously, my power supply is OK and the connections as well. Please don't suspect it anymore.

 

Swede, my ommeter is broken, but I'll fix it soon.

 

Today I observed some things :

-With the electrodes immersed, I took an old spoon and I touched it to the anode, on the mesh and on the bare titanium. The amps were high, 7-to 8, there was current flowing through the electrolyte. There were bubbles on the cathode.

-I also observed that there is current flowing, but veryyy little. There are tiny bubbles on the cathode at 5 volts. I tried connecting the cell to 12V for a few second, there was 1A current.

 

I have now put both electrodes in a 10% HCl solution. I tried connecting them at 5V for a few seconds, and again there was this tiny current flowing.

 

So my conclusion is that there is current flowing, but the anode's resistance has become incredibly high in electrolyte.

 

Some of my friends suggest that I could've "poisoned" the MMO somehow, but I don't know how it could be possible. I'm verry worried.

 

The KCl I'm using is fertillizer grade, it is sold in big caked crystals.

I haven't used any additives.

I use tap water, but our water seems to be much more pure than other waters in western countries I've been. its pH is 7.2. I don't know about its ions, but sometimes it's high in iron cations.

Edited March 21, 2010 by 50AE

[Arthur]

In my opinion as there are several electrode sets working well in North America the electrodes start out in good order. However 50AE you have already killed one set and may be killing another set of electrodes. Something you are doing IS different from Swede or Bonny's cell operating procedure.

 

As you say that you have checked all the obvious connection and polarity issues and the PSU is working properly then something is wrong inside the cell. I'd consider that your tap water will have different trace elements from those in North American water -poisoning of the electrode surface is a possibility. I'd look at the impurities in your supply of KCl it's probably different from the coarse KCl available in North America. building up a coating on the anode is also a possibility.

[50AE]

Though I killed my previous set of electrodes because of the high voltage. But they lasted longer.

 

Edit: As I know, there are many Mn2+ and Fe3+ ions in our water. I also know there are some heavy metal ions, but we can't find any analysis of our water.

My friends have suggested to me to use distilled water from now on, they claim that our tap water is crap.

 

If I have killed the anode, good thing I used the little bonus set and not the large one.

Edited March 21, 2010 by 50AE

[Arthur]

OK my hypotheses;

Something in your cell operating system or method kills the anode, something that is different from the cells in North America. So that means your water or your KCl. Your first anode became highly resistive so you turned up the voltage to get more current then the anode died mechanically. Your second anode has become more resistive and you noticed this and stopped the current flow, perhaps it would have died like the first if you had turned the voltage up to get higher current again.

 

Can you look at the MMO under a microscope? Does it look like the MMO surfaces that Swede has posted in his Blog. or is the MMO surface covered or filled in, or eroded off. If you scour the surface with a domestic pan scourer does anything change? If you pickle the MMO electrode in HCl does the surface change appearance. Can you compare the appearance of the first and second dead anodes with the appearance of the unused anode

 

What temperature was the cell at when you had it running, Swede has said several times that his cells run hot (about 50 - 60 C) and that the electrolyte is made as a saturated solution at that temperature.

 

If you can recover the original properties of the anode then consider doing a batch with distilled or de-ionised water. -See if this removes any contaminant from there. After that consider carefully recrystalising the KCl

[Ralph]

2 chlorate cells running Swede's lovely electrodes down south (Australia) so its not that they are partial to the "northern american climate "

 

 

edit: im running a 5L cell at 5v my electrodes are close together and i run from 30-50amps (depending on temperature as it is run out side and it will go from 65degrees right down to 20) I am using KCl of average purity (technical grade) when it gets really cold and my current drops (as does most of the soluble particles from the solution) i get next to no bubbling a couple hours later (because obviously it is cold in the morning) once it warms back up i get a lovely high current and lots of bubbles I have processed just under 20kg of KCl with my anode cathode kit and a freind of mine (we ordered together) has also been producing large amounts of chlorate he is running a slightly smaller cell in doors (gas is vented out side) and runs a much lower current he has produced alot of KClO3 also

Edited March 22, 2010 by Ralph

[50AE]

I remember using pure grade KCl, when I was running the cell with my first pair of electrodes.

So I think we can partially exclude the KCl from the list.

I've also ran my cell at 55C.

 

I compared the poisoned anode with a new one.

It seems to be a more lighter dark color, dark-gray color than the new one. But its surface is smooth.

The problems is that I'm comparing them after the immersion in HCl. I don't remember if it was grayish before.

 

The first dead anode looks more like the new anode. I'll immerse it in HCl as well to see if it will change color.

Edited March 22, 2010 by 50AE

[Swede]

Did you scrub the cathode yet? Make it shiny with an abrasive like kitchen cleanser.

 

Current density - what is the dimension (length x width) of the problematic anode, and the typical current you ran it at?

 

50AE, the ohmmeter test WILL reveal if there is some sort of surface contamination. I have seen bad MMO that measures in the megohm range, when it should be a few ohms. An HCl bath cured it. That black stuff should be highly conductive, and there must also be a path from the underlying titanium, through the Ti-MMO interface, to the exterior of the MMO.

 

If you get an ohmmeter, also try this... if the MMO to MMO path checks good, also test the top of the Ti shank to the MMO at the bottom. It too should be fairly low. If high, it shows some deterioration between the anode's overall Ti-MMO junction. This phenomenon is what kills many homemade Lead Dioxide perc anodes. The Ti passivates, gets an oxide skin, and even if the LD adheres well, there is no conductivity between the Ti substrate and the LD.

 

If all else fails, I will send an anode that is 100% pure, brand new DeNora; nothing better out there.

Edited March 22, 2010 by Swede