making potassium (per) chlorate

[WSM]

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

 

I had considered using (compatible) floating polymer balls in a chlorate cell, but have opted for the tight lid, instead. Plus, a thick PVC lid is an ideal location for placing fittings and electrode supports, et cetera.

 

I'm inclined to agree about moving the power supply away from the cell.

 

WSM

[WSM]

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.

 

That sounds like good rationale for avoiding the use of stainless steel in chlor-alkali cells. Stainless steel may contain myriad metals but fundamentally it's iron, chromium and nickel. I prefer to avoid any and all unwanted ions in my cell.

 

WSM

Edited May 4, 2016 by WSM

[lloyd]

I'm REALLY confused here....

 

I'm a practicing EE... I know just a little about 'conductors' and crap like that -- been doin' it professionally since 1971!

 

WHAT THE HECK is the problem with making the feed lines to the cell longer? If you have a problem with 'conduction', then make them LARGER than required by the current demand -- I mean... C'MON! It's JUST WIRE, for heaven's sake!

 

(WTF am I missing in all this basic electrolysis stuff that makes the length of the wires so darned important? You could make them MILES long, and it would still work just fine!)

 

LLoyd

[MadMat]

Yeah,

Unless you are making a rather large cell requiring over 50+ amps, longer wires are just fine. People that have worked in the electroplating industry may get a little skittish about long conductors, but they have to remember that big plating tanks with a large/many parts in them require massive amperage, nothing like what a home perchlorate cell would require.

As far as chromium goes, chloride ions and electricity (positive side only) will dissolve it rather easily, in fact, hydrochloric acid is sometimes used to strip chrome plating off parts. but you have to remember, if you are using a stainless steel cathode, it is on the negative side of the cell. This eliminates the possibility of the chrome dissolving.

 

One other thing about a tight fitting lid... gasses are being evolved during electrolysis, the most important one being hydrogen. This has to be vented off and I don't like the idea of hydrogen being collected in an enclosed space (boom!)

Edited May 4, 2016 by MadMat

[WSM]

I'm REALLY confused here....

I'm a practicing EE... I know just a little about 'conductors' and crap like that -- been doin' it professionally since 1971!

WHAT THE HECK is the problem with making the feed lines to the cell longer? If you have a problem with 'conduction', then make them LARGER than required by the current demand -- I mean... C'MON! It's JUST WIRE, for heaven's sake!

(WTF am I missing in all this basic electrolysis stuff that makes the length of the wires so darned important? You could make them MILES long, and it would still work just fine!)

LLoyd

 

You're right, Lloyd. It's simple stuff, if you play by the rules.

 

WSM

[WSM]

One other thing about a tight fitting lid... gasses are being evolved during electrolysis, the most important one being hydrogen. This has to be vented off and I don't like the idea of hydrogen being collected in an enclosed space (boom!)

 

A tight lid, but not a pressure vessel. The cell is vented to safely remove the hydrogen produced (to atmosphere, away from any source of spark or ignition). The tight seals are designed to reduce the salt creep that inevitably appears around things connected to the cell without a perfect seal (including electrodes, the lid itself, thermal sensors, pH control elements and yes, even the vent).

 

Part of it is from the breaking H₂ bubbles, heat, moisture and salt spray (all from the operating cell), causing the salt to migrate anywhere it can through the openings in the cell. This can be greatly mitigated by ensuring a 1 atmosphere (no pressure difference between inside the cell and outside it) environment with proper venting (size and length matter) to help prevent pressurizing the cell. Using round leads and sealing them in compression fittings goes a long way toward preventing corrosion of the copper leads feeding the electrodes (Thanks for that one, Swede).

 

Ensuring the proper application of the dilute acid required to afford the pH control required for optimal performance and production by the cell. The acid needs to be injected well under the surface of the mother liquor and diffused slowly, where any chlorine released will be kept in solution and not released as gas .

 

There's more and it's all tied together (everything affects everything else) and is complicated. Thanks for bearing with me as I try to make my thoughts clear.

 

WSM

Edited May 4, 2016 by WSM

[schroedinger]

WSM did you ever think about using the lid and balls? The lid with all ports to seal the cell of and the balls to reduce the salt creep and spray that hits lid.

[MadMat]

WSM, Don't take my comments in a bad way. You know what your doing; My comment was for the benefit of others who are reading this and might try it without realizing the danger of collected hydrogen gas.

[WSM]

WSM did you ever think about using the lid and balls? The lid with all ports to seal the cell of and the balls to reduce the salt creep and spray that hits lid.

No. Once I dismissed the idea of using the floating plastic balls, I didn't think about them further.

 

If things are reasonably well contained without the balls, are they really needed? Is there a benefit I'm missing by not using them?

 

Maybe you're right. Using both may work synergistically to keep the salt creep problem minimized. This bears further study.

 

WSM

Edited May 4, 2016 by WSM

[WSM]

WSM, Don't take my comments in a bad way. You know what your doing; My comment was for the benefit of others who are reading this and might try it without realizing the danger of collected hydrogen gas.

The hazard of accidently (or worse, deliberately) igniting the hydrogen released by a working cell could be catastrophic. A lapse of judgment like that could easily be injurious if not fatal.

 

There are easier ways to generate hydrogen.

 

Please keep all sources if ignition away from your cells.

 

WSM

[Arthur]

I did see one drawing of a closed cell operated full with a pipe leading out the top so that the inevitable hydrogen could be led out of a hole in the building roof. the electrodes came in from the sides. lots of pumped circulation.

[WSM]

I did see one drawing of a closed cell operated full with a pipe leading out the top so that the inevitable hydrogen could be led out of a hole in the building roof. the electrodes came in from the sides. lots of pumped circulation.

Industrial chlorate cells are combined in series or parallel and the hydrogen vents can be combined in a manifold and vented through the roof of the building, if I'm not mistaken.

 

WSM

[MadMat]

Well I made my first solid lead anode today. I cast pure lead with a length of 12 gauge wire inside one end. The anode is 1/2" in diameter and 5" long. I created the lead dioxide surface by electrolyzing the anode in 10% sulfuric acid @ 35 F. I electrolyzed the anode for 8 minutes, with a current of 9 amps @ 6 volts. It created a real nice purplish/brownish/black surface that appeared to be of a decent thickness. Tomorrow I will start up my test cell. I plan to use a saturated sodium chloride solution adjusted to a Ph of approx. 4. I am also adding a small amount of Whink's rust remover (a source of fluoride and acid for Ph adjustment). I still need to calculate the amount of Whink's I need to add. I am looking for something in the range of 200-250 ppm fluoride ion. If this works out, it will make anodes for a cell rather inexpensive and easy to make. Wish me luck

Edited May 5, 2016 by MadMat

[schroedinger]

Mad llead anodes are nothing new, and they produce perchlorate due to formation of Lead dioxide, bht they aren't stable like lead plated Ti anodes. Whenn the lead dioxide falls of, they also tend to produce some nasty soluble lead compounds.

[WSM]

Well I made my first solid lead anode today. I cast pure lead with a length of 12 gauge wire inside one end. The anode is 1/2" in diameter and 5" long. I created the lead dioxide surface by electrolyzing the anode in 10% sulfuric acid @ 35 F. I electrolyzed the anode for 8 minutes, with a current of 9 amps @ 6 volts. It created a real nice purplish/brownish/black surface that appeared to be of a decent thickness. Tomorrow I will start up my test cell. I plan to use a saturated sodium chloride solution adjusted to a Ph of approx. 4. I am also adding a small amount of Whink's rust remover (a source of fluoride and acid for Ph adjustment). I still need to calculate the amount of Whink's I need to add. I am looking for something in the range of 200-250 ppm fluoride ion. If this works out, it will make anodes for a cell rather inexpensive and easy to make. Wish me luck

 

 

Be careful. I'm not sure about your setup, but with the chlorate cells I'm familiar with, a pH level below 6.0 starts to pump chlorine gas out as it's running. I know the ideal pH for peak efficiency is 6.8, but I recommend not going below 6.0 to avoid this condition.

 

For fluoride, Whink may not be the best source. It's not the HF, it's the other 98% that I'm concerned about, which may cause unwanted issues.

 

Good luck.

 

WSM

Edited May 6, 2016 by WSM

[MadMat]

It's just a test for the anode. The lower Ph is part of testing the durability of anode. I expect the chlorine and have taken steps mitigate it. As far as the "other ingredients" in Whink goes, I guess I will be testing that out as well. If I actually get any perchlorate out of this test run, it will be a miracle.

 

Schroedinger,

 

I am trying to "fix" the problem of the lead dioxide peeling off. You see, there are two forms of lead dioxide, alpha, and beta (it has to do with the crystalline structure). While one form is more conductive, it is also brittle. By adjusting the parameters in which the anode is oxidized, I am trying to control the formation of alpha and beta lead dioxide. Finding the right combination of the two, I feel, is the secret to making it work.

Edited May 5, 2016 by MadMat

[Arthur]

IIRC Swede'd blog on here recorded some of his work to get a robust lead dioxide electrode.

[schroedinger]

Mad did you read the geocities site about chlorate cells? You need the beta form, which gets plated on by using high amperage / cm^2.

Plating has the advantage, that you plate on top, if you just oxidize the allready existing metall, you start to oxidize the outer layer, and then the layer below it oxzidizes and swells, cracking the outer layer.

 

But i would like to hear from your experiment.

[MadMat]

Yes, I've read the information on plating lead dioxide in different substrates. It is just that lead anodes that have a layer of lead dioxide formed on them are used extensively in chrome plating. I want to see if I can make them work for a chlorate cell.

[Arthur]

GSLD is the Holy Grail of amateur production, it enables one cell production of Perc straight through from chloride. However getting a good hard Lead dioxide layer on graphite isn't trivial.

 

One important consideration is the contaminants that form with the perc product. Anything with bits of lead from the electrodes will be considered toxic.

[MadMat]

My plan is to run the cell with sodium chloride and precipitate out the potassium perchlorate by adding potassium chloride, as long as I filter the solution before adding the potassium chloride, lead contamination should be very low. Additionally, If you are that worried about lead, you shouldn't use lead media in your ball mill.

[Mumbles]

Keep us posted.

 

Most of the electrode information I've seen plates out lead from solution. Typically a pH controlled lead nitrate solution was electrolysed to prepare the surface onto your metal or substrate of choice.

 

You also may want to take things in steps to begin with. Chloride to Chlorate, then Chlorate to Perchlorate typically require different conditions and electrical requirements. I have no doubt that a single stage system can be achieved, but working stepwise may help to troubleshoot more efficiently.

[WSM]

My plan is to run the cell with sodium chloride and precipitate out the potassium perchlorate by adding potassium chloride, as long as I filter the solution before adding the potassium chloride, lead contamination should be very low. Additionally, If you are that worried about lead, you shouldn't use lead media in your ball mill.

 

As Mumbles suggests, I've found it better to separate the two processes; 1) Chloride to chlorate, and 2) chlorate to perchlorate. Mainly, this is to end up with a pure product (potassium perchlorate) in the end. (for an idea of my journey, read my blogs and you'll see where I'm coming from).

 

There are several separation and purification processes needed between the oxidizer building steps that are required in order to achieve the final goal (high quality potassium perchlorate), unless you're willing to make your system as complex as an industrial setup.

 

There is no free lunch. If you want good results, you need to take the steps necessary to get them (and they need to be taken in order, without skipping any).

 

If you want to go ahead and try it, by all means, proceed. I may be over-thinking this, but I can foresee some problems if the proper purification steps aren't minded along the way.

 

WSM

[WSM]

It's just a test for the anode. The lower Ph is part of testing the durability of anode. I expect the chlorine and have taken steps mitigate it. As far as the "other ingredients" in Whink goes, I guess I will be testing that out as well. If I actually get any perchlorate out of this test run, it will be a miracle.

 

From the article I've seen, during the run from sodium chloride to sodium perchlorate, the first half of the run cycle time was converting the chloride to chlorate. It wasn't until the chloride was diminished to below 10% (and the chlorate level reached maximum) that the perchlorate began to form. As the run continued from there, the chloride all but disappeared as the chlorate levels were diminished and the perchlorate levels did rise.

 

Several conditions were specified to promote this series of changes, and I suspect omitting any one of them could seriously reduce the desired result.

 

I look forward to seeing what will be learned from your efforts. Good luck.

 

WSM

Edited May 6, 2016 by WSM

[WSM]

I recently acquired some hydrometers with a specific gravity range from 1.000 to 2.000. I'm doubtful they'll help with the sodium chlorate system, but with the potassium chlorate system they can quickly (and easily) show when the end-of-run is accomplished (read my blog number four).

 

Two highly respected and experienced, fellow amateur electrochemists, have suggested using the specific gravity measurement to determine when the run was completed. I plan to try it myself as I do potassium chlorate runs in the future.

 

WSM