noob question on chlorate cell

[nish]

I had a general question on chlorate cells. I watch this video by the guy that a few ppl don't care for (lack of safety notes etc)

https://www.youtube.com/watch?v=G-p7cUzOoi8

 

for the kcl salt solution for making kclo3; how much salt, saturated, or supersaturated?.......

 

 

 

I added a bunch of kcl, about 2 gallons by volume of kcl water softener salt

stuck in an immersion heater and it all dissolved... then I took out the heater and overnight as it cooled, most of the kcl salt recrystallized in the bottom of the bucket.

 

Do you just run the cell with a bunch of solid kcl in the bucket?

How do you know if the stuff in the bottom of the bucket is done/ what you want (k chlorate) or just kcl that didn't dissolve / process?

 

 

Thanks

-Nishan

[MadMat]

You don't want undissolved KCl in the cell. KClO3 has a rather low solubility (7.3g/100ml@20C) in water and you "harvest" it by removing the crystals that form on the bottom of the cell. I would make your KCl solution in a separate container, without heating it. Then pour the clear solution into your cell.

If you plan to produce perchlorate, start with NaCl. After the electrolysis is complete, you add KCL to precipitate out the KClO4

By the way, the solubility of KCl is 34.2g/100ml @20C, this gives you a bit of perspective on the difference in solubility of the two different chemicals.

Edited May 12, 2017 by MadMat

[MrB]

The crystals should look different for starters.

I know people run with more KCl then can be dissolved, either hoping that it will dissolve as KClO3-KClO4 forms, and drops out of solution, or as the heat increases solubility.

I have no idea what their success rate is. The end product will need to be purified using the salts different solubility at different temperatures, if you want to make sure you got reasonably pure KClO3 or KClO4 anyway.

 

WSM has a huge thread that pretty much has all the answers, but at this point the thread is so huge everything has been asked at least 3 times, answered like 5, and completely buried by the next 100 pages of the thread, or so... Read his blogposts on the topic, it's up under blogs, you cant miss it.

[nish]

ok, thanks for the information =)

 

would you happen to know the temps for recrystallizing kcl and kclo3?

I'll try to look over the blog again sometime but its a ton of stuff / not that fun to do a second time honestly

[MadMat]

This might help you out. I generally don't count on the accuracy of wiki anything, but this table seems to check out (as far as the few chemicals I have double checked https://en.wikipedia.org/wiki/Solubility_table

[nish]

Thanks =)

[MadMat]

Yes, the crystals of KCl and KClO3 would look different, but to me, sifting through the crystals to separate them seems to be a huge PITA.

[nish]

I got this from olevonpoff @ FW ... I feel the need for someone to make a book titled " The Idiots guide: making chlorate" lol -nish

Hi, I got my platinum cell set up, I'm ready to give it a try. I did have a couple questions I hope you can help me with.

Do you use a clear solution of kcl or do you put a bunch of extra solid kcl in the cell with the expectation that it will dissolve and keep producing more kclo3? I heated the water up to dissolve the salt but a lot of it recrystallized in the bottom of the container when it cooled down.

If needed, how to you separate kcl from kclo3, I'm guessing its filtered at some specific temperature?

RE: olevonpoff

Hey. Yes I boil up the kcl and mix in as much kcl as I can dissolve. Then before it cools down get it in the cell and turn on the power that should make it stay hot. You should just rinse the crystal with icecold water through a filter. The kcl should run away then

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I think I'm all set now I'll go with a clear solution as madmat suggested and regularly keep an eye on it / filter out kclo3 participant and replace electrolyte bath maybe it will be easier and have less waste. I know with the platinum electrodes I don't want low levels of kcl or damage to the anode increases.

-Nishan

[MrB]

Yes, the crystals of KCl and KClO3 would look different, but to me, sifting through the crystals to separate them seems to be a huge PITA.

Seams like a weird way to do things. We already established that chloride, and chlorate has a rather substantial different in solubility at a wide range of temperatures. Looking at the crystals would tell him if the system actually eats the chloride that wasn't in solution at the start, and if it does, when the system starts getting near the end of the run due to depleting the chlorate storage.

An icewater wash would separate out chloride from chlorate.

[MadMat]

Another suggestion, and this you will have to look up to confirm, but there are catalysts that can be added to improve performance of your cell. Why I said you would have to confirm is because I'm not sure with a platinum anode. But with lead dioxide anodes a small amount of flouride added to the electrolyte improves the efficiency quite a bit. We are only talking about 200 ppm of flouride, so yeah, it's a fairly small amount. I can't remember for sure, because I only know about lead dioxide anodes but dichromate can be added for a different type of anode (don't know for sure if it's for platinum or not). I use lead dioxide anodes because I have laboratory experience in the electroplating industry and they use lead dioxide anodes for chrome plating and... they also use a flouride catalyst for chromium plating.

There is also ratio of anode to cathode surface area you want to establish. Basically what you want is to have more cathode surface area than anode. In electrochemical reactions the current density on the anode and cathode is important. Current density is important for the reaction to occur. You want a higher current density on your anode because your chlorate can actually be reduced back down to chloride at the cathode, but if the current density is kept low on the cathode, that is kept to a minimum. The catalysts also keep the reduction of the chlorate to chloride to a minimum.

 

WSM suggests a 2:1 ratio of cathode to anode. I personally feel you could go as high as 4:1 without any problems. Remember, current density is what drives the reaction. So, keeping the current density low (high surface area for the amount of electrical current) on the cathode will keep the reduction of your precious chlorate back down to chloride at a minimum. Conversely, a high curent density at your platinum anode (smaller surface area) will oxydize the chloride to chlorate faster. The amount of current on both the anode and cathode is going to be the same (total amount of current going through the electrolyte) so the only way you can change current density is to change the relative surface area on the electrodes.

Edited May 14, 2017 by MadMat

[nish]

thanks 200ppm seems easy/clean I think this page mentions additivesHere at the bottom of the page.

 

 

here's a zip with photos of my project http://www.pyrobin.com/files/clorate%20cell%20parts.zip

Somewhere on here I read it might be a good idea to use 2 cathodes on each side "to more evenly wear the surface of the Pt anode..?" ... not knowing 100% what I was doing I took that rout and ended up with 2x andode surface area covered. I have more Ti mesh I could spot weld on to make a 1-4 ration instead of a 1-2 ratio. That would also increasing the current draw making the cell get hotter?

 

 

Just for future reference where can a person buy lead dioxide anodes & flouride ?

 

Any good options for vacuum aspirator pump?

I found this $32 overpriced piece of plastic that requires an adapter. It would be nice to get / use a vacuum Buchner Funnel

[MadMat]

Lead dioxide anodes come up on ebay from time to time. As far as the flouride goes, the cheapest way would be to buy Whinks Rust remover (available at Menards). It contains hydroflouric acid. Be careful!!! HF is very dangerous stuff. I am a little surprised it is actually sold to the public (it is rather low concentration though). For that matter, all flouride salts dangerous. They will etch glass. A little on safety: hydrofluoric acid (HF) can cause serious burns but thats less than half the story. Fluoride ions have a great affinity for calcium and will absorb through the skin and bind with the calcium in your body. Since calcium is needed for proper nerve signal conduction and muscle contraction, when it is bound with fluoride, your heart can stop. I had to go through a safety seminar because the metal treating plant I worked in the lab at utilized large tanks of HF for pickling stainless steel. It was said that skin contact with a strong solution of HF the size of a 3"x5" index card was enough to kill within ten minutes. To add to the problem, if you neutralize HF with, say, baking soda (sodium bicarbonate), the remaining fluoride salt will still burn you... Nice huh? Granted the Whinks product is dilute, but that is no reason to relax safety gear when working with it (gloves and safety googles are a must). At the 200 ppm (approximately) in your cell the fluoride would be rather tame (think fluoride toothpaste), but when making additions, BE CAREFUL!. You could also go out and simply buy sodium/potassium fluoride. this would be easier to work with. There are chemical supply vendors all over the website that sell it, but be prepared for sticker shock. Try to stay with technical grade... anything more pure is going to be very expensive.

[nish]

Not seeing any Lead dioxide anodes on ebay at the moment, any chance the same seller has more

227g NaF for $10, I'll go that route, HF acid is definitely nasty stuff, I didn't know the 3"x5" stat o.0

 

 

I found a listing for 300W rated 0.2ohm potentiometer I thought someone else might also be interested. I bought a couple of them, new price from mouser $48, ebay surplus $5 plus $13s&h I wish they had it in 0.3ohm instead. I'm using a battery charger now, but I'm thinking to be able to use a switching power supply I need a big A** power resistor, I could be wrong.. math isn't really my strong point : $ it should get me minimum current of 25A -> more using one or less current if using both in series. I'll probably run it 15-25A

[MrB]

While it IS more expensive, people tend to use S-150-5 or S-300-5 for 4.5-5.5v systems, and S-150-7.5 or S-300-7.5 for 6+v systems. (max output is 8.3v according to the specs.)

eBay has em. For graphite, or lead-dioxide anodes, i'd use a 5v powersupply, and pretty much just adjust it as low as it can go. If it still outputs to much current there is a mod, outlined here, but i would just space the anode and cathode further apart instead.

[MadMat]

Agree with MrB if you are limited with voltage adjustment you can control the current by simply moving the electrodes closer or farther apart. I don't know if perc/chlorate cells are sensitive to ripple current, but a car battery charger is going to have tons of it. It's because there is only a diode rectifier and no filtering. You can fix this by simply putting a big electrolytic capacitor in between the positive and negative lines. You would want one that is at least 5,000 microfarads (uF) and larger is better also you want a 16v or higher voltage rating.

Edited May 14, 2017 by MadMat

[Arthur]

Cells with platinum electrodes are extremely sensitive to volts ripple, they should have a good DC supply with ripple in the milli volt range.

[lloyd]

I find it very hard to imagine that 'millivolt ripple' in a chemical cell would make much difference. I agree that a fairly-well-filtered DC supply improves matters, but claiming that millivolts will make a difference in ANY electrochemical reaction (worth our pyrotechnic effort) is 'stretching things' a bit.

 

Although I didn't 'run the numbers', I more-agree with MadHat's strategy of just putting a big electrolytic on the output, and letting it run.

 

Lloyd

[MadMat]

I know it's a completely different animal, but ripple in the millivolt range (high in the millivolt range though) will mess up chrome plating in a big way.

Oh yeah Nish, if you put an electrolytic cap on your charger, make sure to observe the polarity. Electrolytics hooked up backwards pop and large ones can pop pretty loud.

Edited May 14, 2017 by MadMat

[lloyd]

Exactly why are we doing "chrome plating" in this particular cell?

 

Just askin'

 

Lloyd

[MrB]

I think he was more suggesting along the lines that ripples might make a difference in some circumstances.

Anyway, personally i think a battery charger is an around bad idea for a project like this, but i haven't seen any issues i'd like to blame on the ripple from using a PC PSU, or one of those i suggested above.

 

More on topic, and away from that track:

 

A high efficiency PC PSU, would put you, well above the 80% efficiency of the dedicated PSU, but might also require a fair load on the 12v circuitry for the voltage sensors to function as intended, and provide an accurate voltage. Something like a 12v 50-100w lightbulb should bring it in range well enough that even a "cheap" PC PSU would be stable. But at that rate you are wasting so much energy just to make sure you are getting stable voltages, that the dedicated 5v PSU starts to look pretty good...

(The reason PC PSU might be a poor match is simply due to a lot of cheap designs using the 12v rail as a reference for all other voltages, and without a load on it, the results get... funky. This is since "most" of the things actually needing power in a PC these days is powered mainly of the 12v rails...)

Anyway... a dedicated, somewhat adjustable power-supply with low ripple, seams ideal. And, they are cheap.

[MadMat]

I use a 650 watt pc power supply myself. Lloyd, I did say it was an entirely different animal (chrome plating that is). But chrome plating does use lead dioxide anodes and one of the problems caused by ripple in chrome plating is decreased life of the anodes so....

[lloyd]

Phttt! 'Ripple', yeah. Millivolts... naaaahhh! C'mon!

 

I'm NOT a 'chrome plating' fellow, but I am an electronics engineer by my last career -before fireworks took me over, body and soul- and I know how ripple affects things, both electronic and chemical. I've done many electro-chemical experiments. And still, that's NOT to say I'm 'expert' at them. But...

 

IF you're talking "700 millivolts", yeah, that's a lot. If you're talking about a couple of tens of millivolts -- no way!

 

Lloyd

Edited May 15, 2017 by lloyd

[MadMat]

Its been a long time since I worked in that field, so I don't remember what was considered the max ripple allowed but I do remember it was more than "tens of millivolts". If I had to guess I am thinking more than 150 millivolts ripple would cause problems with the plating adhesion and possible polarization of the anodes (loss of conductivity). A cheapo auto battery charger especially with a halfwave rectifier or when you use two diodes and the centertap of the transformer would have a crap load of ripple. But either way, putting a cap in there would clean it up. If memory serves, it might jump up the voltage a bit though.

[lloyd]

1.4x the RMS input voltage, Max.

 

And yeah.. 150mv ripple might be a lot for some processes, but that's a LOT of ripple for modern supplies! 10mv would be a lot!

 

 

A battery charger isn't exactly what I'd call a "good" power supply for much of anything -- except charging lead-acid batteries!

 

Lloyd

Edited May 15, 2017 by lloyd

[nish]

I think I'm going to turn it off till my other parts get in, it would suck to kill a platinum electrode so soon.

I added a 25V 9000UF capacitor bank, it helped some, but my digital voltage/amperage meter is very flickery to the point it dosen't work still.

 

The idea of using one or 2x 0.2ohm 300W power potentiometer should work right?

Moving the electrodes would work too, but I don't want to buy another gama seal lid, and everything's fits nice as it is.

 

i"ll also try adjusting the voltage pot on the psu like MrB said

Edited May 15, 2017 by nish