making potassium (per) chlorate

[PTFE]

sorry for those multiple postings but I've just found a really really nice seller of MMO on ebay.

Its a seller in the US. his name on ebay is gallium_guy

 

https://www.ebay.de/itm/MMO-Iridium-Ruthenium-Oxide-Titanium-Mesh-Anode-2-x-3-with-stem-handle/293468557954?hash=item445416d282:g:gsMAAOSwO5VeQJ4r

[Pyrophury]

My electrodes had a bath in 20% HCl for over 3 hours and came out looking pristine, but when I tried them again I still only got about 1A. I'm at a complete loss...

[PTFE]

My electrodes had a bath in 20% HCl for over 3 hours and came out looking pristine, but when I tried them again I still only got about 1A. I'm at a complete loss...

I really feel with you and I'm hoping that we could estimate the problem which is responsible for the low current draw.

 

Could you verifiy that the Circuit is all fine, does the powersupply do its job? (maybe take a graphite rod out of a pencil and use it to short your supply. it will glow red hot when enough current is flowing so be prepared! )

 

Are the connections of the electrodes to the titanium rods okay? Maybe there is a weak spot at one point in the circuit.

 

If you have an adequate multimeter you may be able to test the resistance of the electrodes from the cable connection to the surface.

 

Another idea could be to ask Tiaano on facebook. write in detail what problems you have and they may could give you an answer what can happen to an electrode.

https://www.facebook.com/velappan.jeyakummar.3

Edited February 14, 2020 by PTFE

[Pyrophury]

The power supply appears to be OK, nothing smells burned out. I shorted the leads across the lead of a pencil, it only drew about .2 of an amp at 6V and didn't even get hot. I've checked for any weak connections with a multimeter and cant find any. Perhaps it's the power supply then?

[PTFE]

The power supply appears to be OK, nothing smells burned out. I shorted the leads across the lead of a pencil, it only drew about .2 of an amp at 6V and didn't even get hot. I've checked for any weak connections with a multimeter and cant find any. Perhaps it's the power supply then?

the pencil should only serve as a resistor with low resistance to not completly short the PSU.

Maybe 6Volts are to low for adequate current flow.

you could use the lead like a variable resistor, connecting the minus pole to one end and sliping over the lead with the + pole.

The shorter the distance on the pencil lead the smaler the resistance will be.

 

With the multimeter you should have readings in the Milli-ohm range. I never did that on an coated anode though but i assume thir resistance should be quite low.

[PTFE]

If shorting the PSU directly im sure It will go into over current protection and cut off the power on the output.
A 12V halogen lamp could may be used to test the PSU.
Another stinky way is to use 1m of really small diameter cable and use it to short the supply. but the insulation will get burned.

 

If you have resistors with high wattage aviable a 1ohm resistor could also be used. At 6V a current of 6A should flow through a 1Ohm resistor.

Edited February 14, 2020 by PTFE

[markx]

The power supply appears to be OK, nothing smells burned out. I shorted the leads across the lead of a pencil, it only drew about .2 of an amp at 6V and didn't even get hot. I've checked for any weak connections with a multimeter and cant find any. Perhaps it's the power supply then?

It would be very unlikely that the problem is in the power supply....they either work or they very obviously don't. As in blown fuses, black sooty stains on pcb and main switches busted to bits obviously. Since yours has not let out the magic smoke, I would assume it is ok. Be aware that the switching power supplies usually have a short circuit protection at the output. If a low enough resistance is connected to the output, the supply shall switch off to prevent the semiconductors from burning out.

From the description of events that you have presented here, it looks like a classic case of passivating the anode. Current drops, voltage is raised in the hopes of rectifying the issue and the passivation progresses at a faster pace as a result. The current density raises, as more and more of the surface becomes inert and nonconducting.....if the current density raises then also the polarisation of the anode rises and passivation accelerates. It becomes a positive feedback loop....

It could also be that you deposited a layer of nonsoluble silicates on your anode because the salt that was used contained a silicate based anti caking agent. Fine grained table salt often does and I myself have managed to kill a trusty and seemingly immortal MMO anode due to that. If you let your anode dry off completely and look at it closely, does it appear to have a fine grey deposit on the otherwise rather dark MMO coating? If it does then it is likely that silicate deposits have blocked the surface causing a sudden drop in conductivity . These deposits are very very hard to dissolve, but not impossible. Acids do not work, but hot concentrated alkalies like NaOH or KOH do eat away on these silicate deposits very slowly: hours and days of soaking in a heated bath should restore at least some functionality to the dead anode. I have not yet tried to resurrect my own anode with alkali, as I have so much stock and no suitable container or setup to immerse the electrode to......in short, laziness and lack of motivation are to blame Also I can not yet comment on how or if this kind of a treatment affects the MMO coating. In theory it should survive the alakli treatment, contrary to the stubborn silicates, but there might be some surprises, just saying. On the other hand....if the thing is already screwed then put your mind at ease, you can not screw it up even more by a high pH treatment.

[Pyrophury]

You're right, it's definitely the anode. I just jerry-rigged my other MMO anode (it doesn't have a strap) and the current immediately shot up to 10A.

 

 

The surface of the anode does look duller, dusty-like when compared to the unused anode.

 

How can I prevent this passivisation in the future? I'm using water softener tablets that have <1mg/Kg anti-caking agent.

 

Could it have been the silicate fillers in the silicone grease I used on the gasket, I was quite liberal with it?

Edited February 14, 2020 by Pyrophury

[markx]

You're right, it's definitely the anode. I just jerry-rigged my other MMO anode (it doesn't have a strap) and the current immediately shot up to 10A.

 

The surface of the anode does look duller, dusty-like when compared to the unused anode.

 

How can I prevent this passivisation in the future? I'm using water softener tablets that have <1mg/Kg anti-caking agent.

 

Could it have been the silicate fillers in the silicone grease I used on the gasket, I was quite liberal with it?

Any source of silicon can in theory be converted to silicate in the cell conditions, so it might be a good idea to try and avoid them. But also glass contains silicon and it does seemingly get etched in the process. I ruined my electrode when I started using fine grained table salt, which as it turned out, contained a silicate based anti caking agent. Also I made a silicone gasket for the cell and after just one run the anode passivated.

Prior to that I ran the cell countless times with fertilizer grade KCl in a glass vessel that shows clear signs of etching on the internal surfaces and walls. Always used tap water for the electrolyte and never had any issues at all with the anode. The KCl was coarse and presumably contained no anticaking agents, although it contained grease from processing lines and other impurities that had to be filtered out prior to use. Glass can be ruled out as the source of trouble, as I used the same MMO anode for over a decade without any deterioration in glass vessels that notably corroded during the process.

After I made a new cell lid with a silicon rubber gasket and started using NaCl to prepare feedstock for my perc cell, the problems began and I killed the anode. Notably just after installing the silicone gasket. I used a ptfe gaske before, but it was rigid and did not hold the salt creep back efficiently enough. It might be a coincidence that the failure appeared after the new gasket was installed, but it might be the cause. I'm still leaning more towards the anticake being the culprit, but silicone rubber or grease could as well be the source of trouble....so it's a 50/60 situation

[Pyrophury]

I'm going to assume it was the silica which serves as a thickener in the silicone grease, that has been washed down the sides of the the vessel by the condensation/spray and mixed with the electrolyte, which I will now have to discard.

 

Rather than try to revive the passivated anode, I'll remove the strap and spot weld the other piece of spare MMO in it's place.

[abc159201]

I'm going to assume it was the silica which serves as a thickener in the silicone grease, that has been washed down the sides of the the vessel by the condensation/spray and mixed with the electrolyte, which I will now have to discard.

 

Rather than try to revive the passivated anode, I'll remove the strap and spot weld the other piece of spare MMO in it's place.

 

As you mentioned you used silicone grease, I think maybe silicon oil in the silicone grease causes your problem. I use silicone and silicone rubber as the gasket of my cell ,and I don't encounter any problem at all. I think these two are fine but not sure about the silicone grease.

[WSM]

If you are going to reuse the cell liquor then starting with de-ionized or RO water is a good plan.

 

Hear, Hear!

 

If you can't buy pure water, it can be made by setting up a simple solar still with clear plastic sheet and a cup (see google descriptions). Even in Winter, it can be done inside a makeshift enclosure, exposed to the sun (as long as the water doesn't freeze).

 

For that matter, a still can be cobbled together from a teapot and condenser setup.

 

One fellow in Australia who posted here a couple years ago used rainwater for his cell (it seasonally rains a lot where he lives).

 

WSM

Edited February 16, 2020 by WSM

[WSM]

I avoid using table salt because of the added nonsense they put in it. The salt I use the most is the lowest cost water softener salt available (for sodium cells), and whatever form of KCl I can get (usually water softener grade).

 

Since my sodium chlorate cell experiments a few years ago, I've been focusing on purifying my brine before running it in a cell.

 

After vacuum filtering the raw brine, I use sodium carbonate solution in sodium chloride brine (potassium carbonate solution in potassium chloride brine) which precipitates magnesium, calcium as well as iron contaminants. These precipitates are very fine and will settle, over time, to the bottom of the container (I used a 5 gallon [~19 liter] HDPE bucket). After decanting the clear brine off the fine precipitate, I test the pH. Usually it is alkaline, so treatment with dilute HCl will bring it to neutral or slightly acid where it's ready to use as fresh electrolyte. It can also be dried and stored for later use, but that takes a lot of energy input and isn't really necessary for our purposes.

 

Purifying the brine is a bit of work and time consuming, BUT the yield of your cells will be much higher purity and produce better colors in stars, plus be safer to use, generally (fewer compatibility problems). As I see it, if we're going to the effort and trouble of making our own oxidizers anyway, why not strive for quality at least as good as commercial, or even better!

 

WSM

[WSM]

Sorry, I haven't been keeping current with the discussion. I'm at Western Winter Blast, and a bit distracted till I get home tomorrow evening.

 

WSM

[WSM]

As you mentioned you used silicone grease, I think maybe silicon oil in the silicone grease causes your problem. I use silicone and silicone rubber as the gasket of my cell ,and I don't encounter any problem at all. I think these two are fine but not sure about the silicone grease.

 

 

I have, but never used, silicone grease or oil in any of my cell setups. It's not necessary and can add contaminants to the cell (as has already been stated). I have used silicone bathtub caulk in some cases, but not in direct contact with the electrolyte. It holds up temporarily, but not for long term use. It's probably best to avoid it altogether.

 

WSM

[germaniser]

Please check my setup:

 

Small cell:

Glas, 1,5l

2" x 4" mmo mesh anode + 2" x 4" mesh titanium with handle

0,15A/cm² => ca 5,5 A

 

"Big" cell

mmo mesh anode 2" x 6" - cathode will be stainless steel 2" x 6"

Current: (5" in contact with elektrolyt): 9,5A

 

how big should the volume be?
What is the distance between the electrodes?
Temperature?

How do I best connect the MMO grid to the supply line?

First of all for NaCl electrolysis

thank you for your help

[Pyrophury]

 

 

I have, but never used, silicone grease or oil in any of my cell setups. It's not necessary and can add contaminants to the cell (as has already been stated). I have used silicone bathtub caulk in some cases, but not in direct contact with the electrolyte. It holds up temporarily, but not for long term use. It's probably best to avoid it altogether.

 

WSM

 

I stripped everything down and gave it a thorough clean over the weekend. I've also removed the passivated anode and replaced it with the spare piece of MMO mesh.

 

I discarded the electrolyte and started afresh, this time using only deionized water. I was able to get the lid on without any grease no problem, I just warmed the o ring and lubricated it with water. The seal is good.

 

I've started another run this morning, the current is increasing more gradually this time as the cell is already in the water bath - 15A at 22C. If it's anything like before it will settle at about 30A / 50C, fingers crossed...

[Andead]

Ah I never really considered companies because I didnt know whether to trust the quality of the electrodes etc. Thanks alot PTFE

 

no it isnt all that bad. you can get MMO from china or india (Tiaano/india was the company of choise for me. you can chat with them via facebook and they will weld you a complete set of electrodes toghether if you desire toThey manufacture MMO,PbO2 and i think also platinated mesh.)

 

 

My cell is now finally up again and I cant wait to see the final product thanks alot for those who aided me.

[PTFE]

Please check my setup:

 

Small cell:

Glas, 1,5l

2" x 4" mmo mesh anode + 2" x 4" mesh titanium with handle

0,15A/cm² => ca 5,5 A

 

"Big" cell

mmo mesh anode 2" x 6" - cathode will be stainless steel 2" x 6"

Current: (5" in contact with elektrolyt): 9,5A

 

how big should the volume be?

What is the distance between the electrodes?

Temperature?

 

How do I best connect the MMO grid to the supply line?

 

First of all for NaCl electrolysis

 

thank you for your help

 

 

Lets have a look.

 

First you should investigate deeply into this page..there is every information you asked for.

 

http://www.chlorates.exrockets.com/chlorate.html

 

 

using 2"x4" (50mm*100mm) your anode has a surface-area of (50*100)*2=10.000mm2 or 100cm2 for both sides.

 

An anode this size will take 25A and more at 5Volts.

 

 

You should definitley use two cathodes to make sure your anode is doing its job on both sides.

look up for titanium mesh on ebay. it's not that expensive and will not contaminate your product.

 

cell volume for 25A without using a cooling bath should be around 2-3L

(100ml/1A)

 

The electrodes should be as closed together as possible. As cell resistance induces heat, Power will be lost due to heating.

If the electrodes touch each other, an hydrogen explosion will occour, blasting your cell into pieces. Keep that in mind.

 

Temperature should be around 30°C for Graphite and could be as high as boiling for MMO but ~70° is okay to keep erosion low.

MMO will corrode faster at higher temperatures.

 

 

The mmo is best spot weldet onto titanium rods. Those rods then could be mounted using pressure fittings.

 

 

Edited February 17, 2020 by PTFE

[PTFE]

 

Got a little tiny small cell running at the moment. just to keep my mind fresh

[germaniser]

ah, forget that i have two sides.

 

i want to buy a set on ebay. "mmo mesh anode & titanium mesh cathode sed, 2" by 3" with handle"

in my case, than 9 A, i think thats ok.

its better to have a longer life time of the electrodes.

[Andead]

Please check my setup:

 

Small cell:

Glas, 1,5l

2" x 4" mmo mesh anode + 2" x 4" mesh titanium with handle

0,15A/cm² => ca 5,5 A

 

"Big" cell

mmo mesh anode 2" x 6" - cathode will be stainless steel 2" x 6"

Current: (5" in contact with elektrolyt): 9,5A

 

how big should the volume be?

What is the distance between the electrodes?

Temperature?

 

How do I best connect the MMO grid to the supply line?

 

First of all for NaCl electrolysis

 

thank you for your help

The volume you are dealing with is acceptable but unless the volume is low enough that it leads to excessive heating it should be fine. I do not have much experience with calculating exact volumes as I can generate chlorates at will and do not concern myself with all the numbers as I am in no hurry to obtain the product. The optimum temperature is 60 degrees celcius but this is all up to the efficiency you want and how long you want your electrode to last. You can connect the electrodes however way you want but it can not be done with copper as this can form very dangerous copper chlorate. The larger the connection the more current that can flow.

 

I may no be the most informed in this matter but I have given you what i know. Good luck Germaniser

[PTFE]

here is some precious Polytetrafluorethylen..no real news but things start to come together now.

 

 

 

 

[PTFE]

Today I have filtered my small volume of electrolyte due to carbonates precipitating and some titanium bits have settled to the bottom.

The electrode space is only some milimeters at one point and I dont want to risk a short circuit.

 

Also i tried to use some drops of olive oil to prevent foaming due to boiling. But i have to mention that this only produces a kind of chlorinated soap which is responsible for even more foam on top.

 

the video was made before filtration.

 

 

 

 

edit: I also have to mention that cork works rather nicely to make a tight seal. It gets bleached inside the cell but it holds up the harsh conditions.

The yellow color is from the cork i think.

 

The olive oil i used yesterday was also bleached after some minutes and over night when i did not refill the cell with acidic water the PH drifted to alkaline and the olive oil was converted to a soap.

Edited February 20, 2020 by PTFE

[PTFE]

maybe, when the run is finished i try out if silicone sealant is responsible for MMO-failure by adding some fresh silicone to a new portion of electrolyte.