Anodes and Cathodes

[dcberry]

This is a better place for these CSLD/PSLD anodes:

 

Ceramic LD Anode

Plastic LD Anode

also:

a little more on LD

I had posted this in the potassium (per) chlorate thread eariler but better here too!

[Niter]

Thanks, but where can I get solid platinum (wire, rod, chain, preferably mesh) for a reasonable price???

 

For a reaonable price.. If I could get Pt for a reasonable price I'd buy it with both hands, not with chlorates in mind, but rather the upcoming recession.

 

Pt is about $2000 per troy ounce (31.1gr) at the moment. There's no "reasonably priced" platinum out there unless you have a time machine.

 

About getting it, platinum wire and foil are jewelers supplies. Go to your local jeweler/craftsman and he or she can order it for you. You'd still be paying $100 for a bit of metal wire and leave the shop feeling robbed even when you in fact had a good deal.

 

Know the current spot price for platinum and see how much your product is over it, thats how you buy precious metals.

 

 

 

 

I read earlier how plain lead could be used in a chlorate cell, but it shreds a lot of "toxic products". However, these "toxic products" would be Lead (II) hydroxide Pb(OH)2 and that would be just what you need to make Lead nitrate, and Lead dioxide. Lead hydroxide dissolves fast and without toxic gases in any concentration of nitric acid.

 

If someone has a use for powdered Lead dioxide for a composite anode, its very easy to prepare. Basically you take this Lead hydroxide or litharge and dissolve it into acetic acid to get Lead (II) acetate. Pour this solution into ordinary bleach and boil it (thats no cookbook crap) and powdered lead dioxide deposits like so:

 

Pb(OOCCH3)2 + 2 NaOCl --> Pb(OCl)2 --> PbO2 + 2 NaCl + 2 CH3COOH

 

Its Lead hypochlorite undergoing thermal oxidizing decomposition.

 

So, people might do a "dirty"run with lead electrodes and obtain a byproduct that can easily be converted to Lead dioxide anodes or powder.

 

Lead dioxide powder might have potential as a Pb3O4 replacement that is more reactive and a stronger oxidizer. Dragon eggs perhaps? Lead metal, electricity, vinegar and bleach is all it takes.

[Sylar]

I've made lead nitrate, but I can't seem to get a good plating from it

 

I've seen setups using a rotating anode for plating. This seems rather difficult and would require a rill stand or something to operate good enough.

 

I tried plating onto stainless steel threaded rod. I had a partial succes (pinholes, flaking) so I took it out of the plating bath, and washed it with plain tap water. When I came from work today I found the tap water and electrodes all covered in pink fluffy material. Could this be PbO2 reacted to Pb3O4? Ho would it react with plain water?

[Swede]

Ive been thinking, since its easy to buy lead dioxide powder has anyone tried pressing it into an anode? Some people have some pretty powerful presses out there.

This is an older thread, but this is an interesting quote. I can see something like this (pressing PbO2) in an epoxy or polymer matrix, with an exceptionally high proportion of PbO2, being pretty darned solid. A core bar of brass or stainless could be lathe turned to form grooves and undercuts, and embedded in the PbO2/epoxy or urethane mix. Polymers generally exhibit excellent resistance to corrosives. One issue might be the low conductivity of such a matrix.

 

For those who can view U.S. patents, take a peek at Free patents online, patent #3881954. Summary: a PbO2 "battery plate" is formed electrochemicaly, starting with pure lead, onto which a skin of PbO is formed via heat + atmosphere. From there, the skin is transformed via "pasting" an active material of PbO-PbSO4, immersion in dilute H2SO4, and further electrochemical transformation of this layer to pure PbO2, with an exceptionally high mechanical interlock strength.

[Swede]

I have both lead nitrate and lead dioxide inbound in research quantities. Everything I've read and seen on the internet with regards to PbO2 anodes is that they are a bitch, and very complicated. Perhaps there is a way with modern polymers, plastics, and adhesives, to make an anode that will suffice, not for industrial quantities, but for hobby quantities. An industrial anode must withstand probably hundreds of amps (a very high current density) and elevated temps, whereas we have the luxury of being a bit more patient.

 

I don't like toxic compounds. It's very odd, after I ordered that stuff last night, I went to bed, and dreamed about the lead nitrate. Seriously, how dorky is that? Chemistry dreams. In the dream, I opened the container (it was a wide-mouthed HDPE job) and the powder LEAPED onto my face as if it was alive! I remember holding my breath as I ran about, trying to wipe it off my face, knowing I had inhaled a bunch of it. Then I woke up gasping for air. Probably sleep apnea or something. Very odd.

[Niter]

Swede hear me out: What if you take a coarse powder form of PbO2, mix it with some meltable plastic, press the mixed powders to a rod, and then "bake" the rod at a modest temperature.

 

The grains of PbO2 would all be in contact with each other, forming an anode, and the liqufied plastic will then seep through them and solidify on cooling, binding them to a whole.

 

Run a piece of sandpaper over it to expose PbO2 and you got it made

 

Sounds plausible?

[asilentbob]

Not to be a downer, but this has been discussed sooooooooo much at SMDB. Where members have been experimenting on this very seriously for many many years now.

[dcberry]

Not to be a downer, but this has been discussed sooooooooo much at SMDB. Where members have been experimenting on this very seriously for many many years now.

Thank you!

To reiterate:

This is a better place for these CSLD/PSLD anodes:

 

Ceramic LD Anode

Plastic LD Anode

also:

a little more on LD

I had posted this in the potassium (per) chlorate thread eariler but better here too!

Not sure what your guys agenda is but at least give me a comment and let me know if you can use the info if not I'll keep it to myself. No dissing meant here but I'm here to learn and I sure could use a little input.

asilentbob you have a link for me bro? ;-)

[Swede]

asBob, I know it's been beaten to death, but my curiosity has gotten the better of me. More likely than not I'll pull my hair out and give up with PbO2, but I've got some experience with composites, potting resins, castable urethanes, and materials that are not considered traditional. Maybe something will come of it. At least it'll be interesting, and fun.

 

Anything other than a pure, thick coat of PbO2 will exhibit some reduced conductivity, but so long as the current is kept reasonable, heat losses at the anode shouldn't be too much of a problem.

 

A slurry consisting of a high proportion of polymer/PbO2 could be cast, but probably will not have an adequate density of PbO2 to function properly. I think the first thing I'll try is potting resin in a ratio similar to what you'd use to press BP. Just enough to dampen the grains, then press, possibly under a vacuum, onto an undercut metallic core. I'll use a capcitative discharge welder ("sput" welder) to connect a lead to the core mandrel. We'll see what happens.

[tentacles]

There is at least one patent for making PbO2 anodes this sort of way - they pressure cast the resin (at 3000-6000psi) and then plate PbO2 over top. They mentioned trying the cast resin anodes without plating over and this was fail. I seem to remember it was either excessively high resistance and/or erosion. Besides, the PbO2 powder you can buy is -alpha not -beta.

 

dann's PbO2 over Ti scheme has a lot of promise, I'm going to have a balcony soon where I can play with such things again.

[Swede]

Well, I'm diving into electrolytic cells full bore. PbO2 and Pb Nitrate coming, and I picked up some electrodes from Northstar Pyro, both MMO over titanium, and platinum-clad niobium. Whipped up a quick cell:

 

http://www.5bears.com/perc/ns12.jpg

 

These are bubbling merrily... I'm doing the simplest possible process, KCl to KClO3, as an initial run.

 

http://www.5bears.com/perc/ns17.jpg

 

The lead salts have not arrived yet, but I am definitely going to give further PbO2 electrode-making a shot, with some hopefully different approaches.

 

I mentioned it before, but this patent #3881954 really takes a unique approach, one I have not yet seen attempted by amateurs. If the polymers fail, then I'll attempt it, and try to come up with a process suitable for a home shop.

[tentacles]

Have you read through the anode / perchlorate threads over at science madness? If not, you *really* should. They have covered MANY MANY methods of making anodes, and there's really little reason to repeat failures (not that anyone has tried this method mentioned in US3881954). It's been shown that battery type PbO2 anodes will last only minutes in a chlorate/perchlorate environment. Also, the guys over there would be interested in your research as well, and can provide helpful tips/advice/comments. It's all in the technochemistry forum. I could PM you relevant threads if you like.

 

Your best best for making PbO2 anodes is to treat a Ti strip with Sb doped SnO2 (Doped Tin Oxide, or Antimony Tin Oxide) and then plate that with PbO2. The DTO coating seals the Ti and provides a conductive layer. Plate on maybe .5-1mm of PbO2 and it will last fairly well. dann's test anode lasted 3 months straight so far, doing chloride to perchlorate. I think his final chlorate concentration was 11g/l, it was a sodium cell. He used no efficiency additives (ie NaF/ KF/ dichromate etc).

 

Best bet so far is to make cheap MnO2 anodes (will last approx 1 run, but take 15 minutes to make and the Ti strip is reusable several/many times) to do the chloride to chlorate, and then use PbO2 to do the perchlorate conversion.

[Swede]

Have you read through the anode / perchlorate threads over at science madness? If not, you *really* should. They have covered MANY MANY methods of making anodes, and there's really little reason to repeat failures (not that anyone has tried this method mentioned in US3881954).

This is wise advice... I will definitely sneak a peek at what has been done, and try to avoid repeating failures. I was not aware that such a forum existed outside pyrotechnic sites. Should be interesting.

[nath0r]

Swede, i knew those lock 'n' lock containers were good for something

 

Thats a nice little cell you've knocked up there

[tentacles]

That does look like a good cell container, I will check those out soon. What I want is a way to seal in an anode and still be able to remove it. Any thoughts on silicone sealant, possibly mashed in there some which way to maintain the seal (since it won't stick to PP).

[Swede]

I found the "Lock & Lock" containers at Wal-Mart, and after 2 days, it is looking like a winner. The seal is 100% so far. I rushed this cell, and it is not top quality, but so far, so good.

 

The electrodes were inserted through the lid by simply cutting a slot (undersized works best, then force the tang through).

 

http://www.5bears.com/perc/ns10.jpg

 

I roughened up the surface a bit, then blobbed on hot glue. I wanted just a temporary setup, and hot glue cleans off the shanks of the electrodes nicely.

 

http://www.5bears.com/perc/ns11.jpg

 

The interesting thing, as the electrodes heat up, the hot glue softens a little, which is actually a good thing, as it retains a seal and flexes as the cell is manipulated.

 

For a power supply, I was going to use a 30 amp regulated supply I've had on hand for years, but I smoked it about 2 weeks ago, which sucked. Lurking eBay, I eventually STOLE a power supply from a guy - I feel badly about it, actually - an 80 ampere Sorensen linear, which must weigh 80 lb. $26!! It'll be good for plating and anodizing as well as (per)chlorate production. I started the cell at 5 amps, and have been ramping it up slowly. Right now at day 2 it's at 18 amps. At that level, the 3/4 gallon or so of electrolyte is at 140 degrees f. and I don't believe I'm going to go higher without cooling.

 

Starting with a saturated solution of KCl, I would have expected to see some crystals form by now, but I guess I need to be more patient. I'm gathering indicator chemicals as well, methylene blue, indigo carmine, and phenylanthranilic acid. And the lead salts arrived via FEDEX today, so I am all set!

 

Question for you experienced chlorate guys - measuring pH has been a pain due to the hypochlorite content. I have a Hanna pH meter, but it is old and suspect. The best I have come up with is to boil a small sample and use pH paper. At pool stores, they have volumetric titration kits for acid-demand, which chlorine interferes with. Part of the kit is drops which are added to the pool water to rid it of chlorine. I'm going to check those out and see if they are useful, but otherwise, any suggestions for pH measurement is appreciated. Interestingly, the pH initially went up, but after an initial addition of HCl, seems to now remain stable at about 6.00. Thanks.

[Swede]

Here comes the KClO3! This being my first batch, I was surprised at how long it took, and how much current was required, before the KClO3 began to drop out of solution.

 

http://www.5bears.com/perc/ns19.jpg

 

One thing I noticed - at this level of current (20 to 25 amps) "alligator clip" connections frankly suck. There was voltage drop and excess heating at the clip to electrode interface. This was easily solved by a pair of heavy-duty copper wire lug clamps, which can be found at any big-box hardware store.

 

http://www.5bears.com/perc/ns18a.jpg

 

The crystals this morning were piled about 1.5" high at the bottom of this fairly large cell. I am at the point where I am concerned about the dropping chloride level. I'm using AgNO3 as a qualitative chloride detector, but that is useless to detect the end of the run, as that will happen at 10%, when the cell will begin to produce perchlorates, rather than chlorates. This is an MMO anode, and will not work well to produce perchlorates, so I want to get it out of there before it erodes.

 

I put some exceptionally fine crystals under a microscope, and they had the flat plate monoclinic form, looking like tiny fish scales. This KClO3 is probably quite pure due to the good electrodes, and will be filtered, washed, and stored. Some microscopy pics:

 

http://www.5bears.com/perc/ns21.jpg

 

http://www.5bears.com/perc/ns22e.jpg

 

Fun stuff!

[Miech]

You could determine the chloride level by either buying dedicated indicator strips or by titrating your electrolyte with silver nitrate solution. Indicator strips are more precise, since titrating with silver nitrate also percipitates silver chlorate and hypochlorite.

[Swede]

I didn't even know quantitative chloride test strips existed. I was thinking about doing a silver nitrate titration, and Hach, among others, has them on a stick. At less than a buck a test, it's worth it.

 

Hach.com Product #: 2751340 Chloride QuanTab® Test Strips, 300-6000 mg/L, 40 tests.

 

At ~300g/l solubility for KCl, the liquor will need to be diluted, but still, what a great time saver. Thanks for the head's up.

[tentacles]

Swede, at 140F you've probably got 200g/L of chlorate in solution there, so it's no wonder it took a while to get crystals precipitating out. I'd suggest, though, rather than using a batch process, just harvest the crystals

regularly with a scoop of some type. Make a seperate cell for perchlorate. Harvest the KClO3, maybe bother to purify (I wouldn't, chloride levels as low as you'd get would not be a problem) and put in it a KClO4 cell. Now you don't give a damn what the chloride level is, just harvest, remove some liquor, top off with saturated solution and saturate the liquor you removed for the next go-round.

 

One thing, too, you've only got one cathode in that cell, and you really need two. The anode has two sides, so you need a cathode on each side. But Ti sheet on ebay for cathodes, mucho cheap. I've got like 2 sq ft of Ti at home for making anodes and cathodes.

 

Glorious looking crystals.

 

How are you venting the cell gases, is there a hole or hose there somewhere I don't see?

Edited July 25, 2008 by tentacles

[Swede]

Hi Tentacles, I appreciate your suggestions, and they make sense. Chlorate is OK... Perchlorate, much better, and that is the ultimate goal. Venting - I've got a vinyl tube leading outside, and it is rapidly eroding from the chlorine gas. It looks like it'll survive just this one run. I might invest in some tygon or viton tubing for future runs.

 

I've got two electrode sets, one dedicated to chlorate, the other, perchlorate production. Let me see if I've got this correct: Your suggestion is to keep the chlorate cell producing. For the chlorate cell: Pull chlorate crystals out, boil down remaining liquor until saturated once more, top off with saturated KCl, and continue. Using the harvested chlorate crystals, prepare another saturated solution, put THAT in the perchlorate cell, and fire it up. Keep an almost constant assembly-line deal going.

 

I like it. If that's essentially what you are describing, then I think I understand.

 

These Lock & Lock containers are ideal for cells. So far, the silicone gasket has functioned perfectly. I also like the dual cathode concept. Right now, the spacing of the anode and cathode is too great, and it's taking 8 volts to produce 25 amps. A dual cathode would probably cut the voltage requirement in half.

 

Now I need to figure out if I can run two cells in parallel. Shouldn't be a problem. The supply will do 80 amps. If I can keep the resistances similar, I should see reasonably close current flow between both of them.

[tentacles]

Tygon = expensive vinyl tubing. I'd suggest polyethylene, which is very cheap at your local hardware store. It's resitance to chemicals/price ratio is phenominal, unbeatable I should say.

 

That's pretty well exactly what I'm describing, although boiling the solution to saturation is a bit more work than I'd go to - just swap out some liquor for saturated, and resaturate the removed liquor. That way you don't precipitate out KCl on accident. Just harvest what falls out during electrolysis, it will be pure enough to go in the perc cell. Harvest in a similar way from the perc cell, and then recrystallize the harvest from that cell once, perhaps twice if your tests show residual chlorate. Keeps the work to a minimum, and the production continuous as well as keeping the chloride/chlorate level high enough in the cells to slow anode erosion.

 

If you're going to PGI, I can bring a piece of Ti sheet for you on the cheap. I paid like $20/sq ft for what I've got, it's in ~6x12" pieces.

 

I've looked into aquarium pH controllers (paired with some sort of pump, peristaltic probably) for controlling cell pH. It's not much of an issue in a perchlorate cell, but it will affect a chlorate cell's efficiency greatly. Perc, set the pH and more or less forget it since the reaction doesn't affect the pH nearly so much. I think dann found that magnetite will make perc if you control the pH, although it's terribly messy and the efficiency was abysmal.

[Swede]

Good deal. I dialed the amperage way down in anticipation of the first harvest today. The temp has dropped dramatically, and the crystal pile about doubled.

 

I am going to filter the entire cell, collect the filtrate (KClO3), and allow the liquor to dump onto a bed of KCl salt in another container. The liquor has plenty of KClO3 still dissolved, and I want to save as much of that as possible. I'm not sure if the presence of dissolved KClO3 in the liquor will inhibit further uptake of KCl from the fresh salts. I'm guessing very little KCl will be dissolved, but we'll see. I'll weigh the KCl salts BEFORE dumping the warm liquor over them, then reweigh afterwards, to see how much KCl was taken up. If it's inadequate, I'll have to do a liquor swap. No big deal either way, but it would be nice to preserve as much of the dissolved chlorate as possible.

 

Unfortunately I can't make the PGI, but I appreciate the offer. I'll pick up some sheet Ti off eBay and redesign this cell. I'm going to stick with the Lock & Lock container, as it's done so well, so far. And yeah, pH was a pain. It seemed to really take off initially, requiring HCl additions early, but then seemed to stabilize. Just measuring it is a hassle. pH dye indicators are worthless, and the hypochlorites present chew up pH paper like crazy. I'm guessing the lifespan of a lower-grade pH electrode will be very short in the cell environment, which seems to be one of the harshest this side of a nuke reactor.

[Arthur]

The reason for using NaCl as the starting electrolyte is that NaCl is much more soluble than KCl so you can have a lot more ingredient in the cell. This means that the conductivity will go up so the cell resistance can go down so internal heating due to IR loss will be reduced.

 

Sasman on UKPS forum had a cell running at 80a a while ago. He found problems with getting the power into the cell -even the wires and electrode hangers became hot with IR heating. The volts lost in the wiring became high and the cell electrical efficiency suffered.

 

Added

 

Use a large bore siphon tube to take off the crystals and some liquor from the bottom of the cell. Then measure the SG with a Hydrometer and add chloride and water to the original level and SG.Eventually you will have a chart of SG plotted against concentration, and have SG levels at which to add chloride or add water to maintain strength and level. -Pick a temperature and work at that! SG is very temperature dependent.

 

Added again!

 

Cells in parallel is a poor idea because any imbalance in chemistry or resistance would lead to one cell hogging the current and cooking while the other cooled. More or bigger electrodes in the same cell is a better plan.

 

Venting - You may need to pump the fumes out through a water bottle splash trap or let the cell run outside in free air. The connectors will die if they corrode because they will overheat.

Edited August 25, 2008 by Arthur

[Swede]

In earlier posts regarding chlorate cells, I mentioned (and liked) the Lock & Lock style food storage containers. I need to revise my opinion and say thay are not suitable. While the plastic has fogged a bit, the real problem is the seal, and the mechanism for the lid. My guess is that unless you repack the seal, which might be possible with PTFE packing cord, the lifespan of one of these cells is probably only 4 to 6 batches, and that's just not an economical way to do it.

 

I mentioned in my blog that PVC is a superior plastic for this process, and I am going to try and devise a good (and cheap) cell from wide-bore PVC pipe and fittings.