Sciencemadness Discussion Board - Potassium Chlorate from Electrolysis - yay :)

Potassium Chlorate from Electrolysis - yay :)

binaryclock - 22-4-2013 at 19:58

After much reading and experimenting with different anodes, cathodes, jars, glues to make it all air-proof, I finally made a cell that seems to be working really well.

I have to give a thank you to woelen's page available at: http://woelen.homescience.net/science/chem/exps/miniature_ch...

my 2nd reference: http://www.amasci.net/syntheses/potassium-chlorate-synthesis...

and my 3rd reference: http://www.oocities.org/capecanaveral/campus/5361/chlorate/g...

I'm using carbon battery anode and cathodes as this is my first electrolysis experiment with potassium chloride so things are a bit black inside the cell right now. It's been running for about 14 hours now and I have what looks/feels like a good 2cm - 3cm of crystals on the bottom of the 500ml jar I'm using. I've had the temperature peak at about 60c for about 10 minutes until I realized it was that high. Otherwise the temperature has remained under 40c, about 35c-39c.

I have a few questions:

1. Can I suspend the electrolysis overnight and begin it again in the morning? I'm a computer engineer and I've seen what happens to power supplies when they short out.. leaving a cell running overnight on a pc 5v rail capable of 20A without any fuse on it (as it stands right now,) doesn't sit right with me.

2. How long should this cell run before I should call it complete? I'm running at about 1.5A to 2.5A on this current cell and the voltage is about 5.0v to 5.2v. The 500ml solution of potassium chloride was completely saturated when I started the cell. About 30 minutes ago I topped it up with about 40ml of saturated potassium chloride solution and about 2 drops of 31% HCl.

3. I've been using NoSalt as my potassium chloride source which is $7.39 per 311g bottle. Today I was leaving the supermarket and I saw some salts for water purifiers and here is the MDMS: http://www.mta.ca/administration/facilities/safety/msds/Heat... . The 20kg bag was $4.99 :/... Do you recommend buying this bag over the $7.39 for the 311g of NoSalt?

Thanks guys!

[Edited on 23-4-2013 by binaryclock]

12AX7 - 22-4-2013 at 20:27

I had picked up a 50lb (..yeah, pretty much 20kg..) sack of KCl "water softener" salt and made plenty of stuff with it (and with regular NaCl):

I had once made quite a bit (as you can see) over two summers, at not-very-good efficiency as it turns out, but oh well.

The downside to starting and stopping is, it cools down every time, so for the first couple hours during restart, the cell is still cool, and chlorate conversion isn't as efficient. And maybe graphite wear is higher as a result too. If you have a preheater or something, this goes away and it's not a problem.

I used a PSU once or twice as well, and as an EE, I probably have an even more nuanced opinion of what happens to power supplies when they short out. That they lasted as long as they did is fairly remarkable given the impressive salt mist these things put out, even given a splatter cover -- I think it was a few weeks' run time on one, then I fixed the burned out parts, then a component on the circuit board failed, this time pyrolyzing the board itself in the process (I believe it was an inductor -- I had fixed the first fault which caused it to shutdown or whatever, allowing the next priority to fail, an inductor which wasn't rated for, you know, pushing the entire supply's capacity through it!).

What I ultimately went with was a microwave oven transformer (MOT) with schottky diodes (pulled from old PSUs!), filtered with an inductor made from another MOT core. I also used a ballast resistor, since the system produced about 6V at full load current, and I only needed 3.5-4V; a length of heavy steel wire served nicely. Overall, the system proved very robust in subsequent runs.

Tim

binaryclock - 23-4-2013 at 10:07

Okay so I removed the crystals from the black sludge and they don't look like nicely formed crystals, they look like little thin white hairs, but covered with sludge. Are the hair-like crystals something else, or do I have potassium chlorate there? I tried washing them with ice cold water, but the black sludge is all over and hard to remove.

hyfalcon - 23-4-2013 at 12:07

Dissolve in hot water, filter, then boil down to saturation and throw it in the freezer. KClO3 will start falling out as it approaches 0-5C.

Mailinmypocket - 23-4-2013 at 13:28

Firstly, if you can, find some MMO mesh on eBay. It will produce a perfect white product everytime. Using the water softener KCl (don't use the no-salt stuff, they add anti caking agents, not in large amounts but might as well avoid it if possible)
All the times I used graphite I ended up frustrated with at best a light grey product.

A seller on eBay called laserred often sells pieces like this one, which was about 15$ I think. As for the PC power supply, I've used the same one to run about 10 batches over 2 day periods over the last couple years. Never had problems with it failing in any severe way either! I would maybe suggest MMO if you can find some.

hyfalcon - 23-4-2013 at 15:32

Looks like laserred's out at the moment. I've got 4 extra sheets that I got from him. It's about 4" x 12" size wise. u2u me, I'll turn loose of 1 piece if you are interested.

binaryclock - 23-4-2013 at 18:58

Thanks for the replies. What I ended up doing was boiling the entire thing to melt the crystals and get rid of the hypochlorite bleach smell. Then I froze the mixture to -5c or and got 3 distinct layers. On the bottom was 90% of the carbon sledge, followed by pure crystals, followed by the potassium chloride/water solution. I decanted the solution and then tried to scoop the crystals out without disturbing the sludge on the bottom. I put the crystals on some filter paper and underneath the filter paper I put about 5 pieces of folded paper towels. This allowed the water to get pulled out of the crystals without them sticking to the paper towels. What I have now is still hair-like crystals, but they are more pure and probably gray-white with some crystals that are more heavily contaminated with carbon sludge than the others.

As far as the MMO electrodes, you would still need a platinum or titanium electrode as well, right? And when you get the MMO you'd have to weld it to a titanium lead as well, correct? I don't have any welding equipment.

What do you guys think of just getting a pair of electrodes with a kit already to go like this? http://scienceforyou.net/electrolytic-cells/electrolytic-cel...

I'd rather make things myself, but having to weld things is not my forte.

[Edited on 24-4-2013 by binaryclock]

Mixell - 23-4-2013 at 19:55

I'd imagine you can attach the mesh to a clamp or wire, as long as it won't be submerged in the liquid it should be fine (although it is best to protect it from aerosol too). You can even use silver or another corrosion resistant wire.

About the salt, in the MSDS you linked a content of 99.6% sodium chloride is mentioned, if you want a nice crop of crystals, better use potassium (as sodium chlorate is water-soluble).

Regarding the cell, it is very costly. You basically need a MMO anode (available on eBay for 30$, or from me if that Chinese supplier will come through). If you're into electrolysis and have relatively deep pockets, I would consider getting a digital lab power supply with varying voltage/current limitations and shorting/over-heating protection. A good 30V 5A one will cost you 70$-100$. If you have an extra 50$ on your hands, you can even get a 10A one.

Titanium will be a good cathode, you can even use titanium wires (or rods/plates/what ever) which should cost you just a few bucks.

binaryclock - 23-4-2013 at 20:32

That one does have sodium chloride. This one is better: http://www.siftocanada.com/media/filer_private/2011/06/24/na...

I'll need to look for an MMO anode then. If I use MMO for the anode, I should be okay using stainless for the cathode, no?

Also, after drying my first batch of KClO3, I attempted to mix with sugar in a 50/50 ratio. I used about 0.25g of each KClO3 and sugar. I then added about 2-3 drops of sulfuric acid. The result was a snap, crackle, pop with smoke and lots of black stuff in the middle that sizzled, but no flame or fire... i'm assuming that's the carbon contamination? Would 0.25g of each chemical be enough to result in a flame, or should I wait for tomorrow until I can outdoors with larger amounts?

Thanks for all the help.. having tons of fun, but doing it carefully and responsibly of course

PS - My next cell is running now and this time I'm going to make sure the temperature never reaches 40c. That should cut down on the carbon electrodes decaying and casting tons of black carbon in to the solution.

[Edited on 24-4-2013 by binaryclock]

woelen - 23-4-2013 at 23:37

Try the experiment again with 0.25 gram of KClO3 and 0.1 gram of sugar. You need more oxidizer than fuel. You should see fire, even with a lot of carbon in the material.

Did you recrystallize from water or did you simply dry the sludge with crystals? In the latter case you probably have a lot of KCl in it as well.

If you use carbon rods, then you'd better use NaCl during the electrolysis process. With NaCl you don't get crystals, all NaClO3 remains dissolved. This allows the carbon to settle at the bottom and then you can decant the clear liquid with NaClO3 in it. With KCl you then can make KClO3, because the latter is much less soluble than NaCl, KCl and NaClO3. If you use MMO, then it is better to use KCl, so that you immediately obtain nice pure crystals of KClO3.

binaryclock - 24-4-2013 at 05:28

Brilliant on the sodium chloride idea! I had no idea you didn't get crystals with NaCl so that makes filtration much easier from the sludge. It's one extra step, but it'd make nice white crystals in the end.

To recrystallize I just heated up the entire solution, sludge, solution, and crystals to a boil for 20 minutes, let it cool to room temperature, then froze it in the freezer. I then tried to separate the crystals from the sludge at the bottom as best I could. The crystals today look light-gray, however they aren't cube-formed.. they are more like little hair-type crystals clumped together... not bad really considering all the sludge that was in the solution. Are you saying that I should take the dried out crystals I have now, add water to dissolve them, and recrystallize them again?

I'll also try your idea of lessening the fuel and increasing the oxidizer today.

Also, what should the theoretical run time be for this cell if we take the following parameters:

Water: 275ml
KCl: 110g
Water temperature at time of adding KCl: 40c
Average amperes: 2.52A (@ 5.02v)

The way I'm trying to calculate it is:

There are 1.475 moles of KCl.

Time in seconds = ( 1.475 x 96485 A s/mol ) / 2.52A

time in seconds = 56474 seconds, or 15 hours 41 minutes.

Is that correct?

Thanks so much, your webpage was really helpful.

[Edited on 24-4-2013 by binaryclock]

hissingnoise - 24-4-2013 at 11:52

The good solubility of NaCl makes its electrooxidation more efficient than that of KCl . . .
Cell-liquor may be filtered directly to obtain a clean product which is useful in metathesis!
The extra oxygen of NaClO₃ makes it of interest in pyro comps but its hygroscopicity needs accounting for.

binaryclock - 24-4-2013 at 19:30

I've tried to mix 0.25g of KClO3 and 0.1g of sugar and still just lots of popping and smoke. No ignition after mixing with sulfuric acid.

Do you think I have alot of KCl crystals in this? What is the best way to separate the KCl crystals from the KClO3 crystals?

Finnnicus - 25-4-2013 at 00:38

Quote: Originally posted by 12AX7

What I ultimately went with was a microwave oven transformer (MOT) with schottky diodes (pulled from old PSUs!), filtered with an inductor made from another MOT core. I also used a ballast resistor, since the system produced about 6V at full load current, and I only needed 3.5-4V; a length of heavy steel wire served nicely. Overall, the system proved very robust in subsequent runs.

Tim

This being a MOT rewired with higher gauge wire for more amps?
Or some electrolysis trickery I dont understand.

woelen - 25-4-2013 at 01:02

Quote: Originally posted by binaryclock

I've tried to mix 0.25g of KClO3 and 0.1g of sugar and still just lots of popping and smoke. No ignition after mixing with sulfuric acid.

Do you think I have alot of KCl crystals in this? What is the best way to separate the KCl crystals from the KClO3 crystals?

Your KClO3 is not pure in that case, otherwise you certainly would have fire.

Dissolve all of your material in as little as possible of boiling water. Do this by adding a small amount of water to the solid and heat it, until it is (nearly) boiling. Then, while stirring, add small amounts of water, such that the solid material just dissolves while the liquid is kept hot (near boiling).
When all solid material is dissolved, then stop heating and allow the liquid to cool down. If it is at room temperature, put it in a freezer and allow it to cool down further (but do not allow it freezing).
Decant the liquid from the solid mass. The solid mass can be put on a coffee filter, which in turn is put on a pile of paper tissues, in order to draw even more liquid from the solid mass. Then rinse with distilled water and repeat decanting and putting on a coffee filter. Then allow the solid to dry in a warm place.
You will have much purer KClO3 after these steps.

Adas - 25-4-2013 at 06:57

Quote: Originally posted by binaryclock

I've had the same problem when I made NaClO3 using electrolysis. I mixed it with sugar, but after ignition, it just smoked. Probably it contained too much NaHCO3, NaOH and other crap.

binaryclock - 25-4-2013 at 08:06

Thank you so much for your reply!

I have combined two batches of crystals in to a 400ml beaker and added small amounts of about 90c water to it until the solids were dissolved in solution. I then allowed it to cool to room temperature then put it in the freezer to cool to 2c.

At this point about half of the beaker was crystals and half was a water solution. I decanted the solution off the top of the crystals and put in through a filter paper in to my waste jar that I will use for the next cell. The crystals I then took and put them on filter paper with 5 paper towels under the filter paper. They look a lot purer and much whiter now. Instead of hair-like crystals they are cube-like.

It seems like I lost about 50% of my initial crude yield in this re crystallization process which would lead me to believe I had a large amount of KCl crystals in my initial crude yield. At least I put the decanted solution back in my jar to reuse.

Once they dry, I'll report on if I was successful with the sugar/KClO3 + H2SO4 reaction.

Thanks again, it is really helpful.

----

EDIT/UPDATE:

I mixed 0.25g KClO3 and 0.1g sugar and added a few drops of sulfuric acid and the same thing happened - it just fizzed and popped.

At this point it's daytime so I am able to do my experiment outside in the light so I figured I'd just add a lot more KClO3 and sugar and a drop of sulfuric acid because maybe the sulfuric acid is drowning the small amount of mixture I have set out. I probably used about 1g of KClO3 and 0.75g sugar.. I didn't weigh it this time, just wanted to get a good amount on the plate to test with.

Success i'm happy to report that it did combust violently with one or two drops of H2SO4. So it would seem that you need a larger amount of a KClO3/Sugar mixture so that combustion can take place without getting drowned out by the H2SO4.

Next question: How can I measure the purity of this KClO3 I have created?

[Edited on 25-4-2013 by binaryclock]

woelen - 25-4-2013 at 22:44

Good to read that you had success! If you recrystallized the KClO3 then their purity almost certainly is better than 95%. if they were rinsed well with distilled water most likely even better than 98%. If the crystals look only pale grey, then the amount of carbon in them is very low (well below 0.1%). Even just a few tenths of percent of very fine carbon make a solid appear nearly black.

If you want to use your KClO3 for pyro purposes, then there is no need for further purification. If you want to use it as oxidizer in aqueous chemistry, then another recrystallization may be in place. Unfortunately, getting rid of all carbon is very hard.

12AX7 - 27-4-2013 at 08:55

The difficulty of purifying KClO3 is doing it hot, without evaporation. Actually filtering the black gunk isn't so bad; back in the day, I used a plastic jug, perforated bottom, wadded with glass wool. At first, the liquor runs fast and murky through the wadding, then it clarifies as the wadding picks up particles, then finally it slows to a drip as most pores get plugged with very fine particles. (Another common medium is diatomaceous earth over filter paper, which I believe behaves much the same way.) At this point, the filtrate takes its sweet time, but is better than colloidial in performance -- crystal clear. The challenge of filtering KClO3 solution in this manner is keeping it hot (so it doesn't clog the filter) and keeping it from evaporating (so it doesn't dry up and clog). You might need to wash the filter with boiling distilled water, for instance, and evaporate to get it back to a concentrated solution.

This is another advantage of sodium chlorate: except for the most concentrated solutions, it remains soluble and easy to filter. The main disadvantage is the extra precipitation and recrystallization steps in order to get the potassium salt.

Tim

binaryclock - 1-5-2013 at 10:03

Thanks all for your great suggestions and help.

Here is a picture of about 35g of the whitest/purist I could get KClO3 crystals when using carbon electrodes from batteries and KCl to start: http://i.imgur.com/FaVMph1.jpg

However I was able to get much cleaner results when starting with NaCl and then using metathesis to double displace NaClO3 ith KCl to create KClO3: http://i.imgur.com/ZexKMVF.jpg . Because of the lighting it looks like there is gray in the crystals.. it is not that colour. These crystals are as pure as snow.

Stuff works great and have been able to do some great experiments with it.

Thanks for all the help.

[Edited on 1-5-2013 by binaryclock]

12AX7 - 1-5-2013 at 14:57

Yeah, I can still see the specks and grayness in the first sample. The second is as beautiful as it should be.

Tim

binaryclock - 1-5-2013 at 20:00

I did a burn test on both samples side by side.

The "gray" sample, the first one which was synthesized by KCl and carbon anode/cathode to create KClO3 burned a good purple.

The second "white" sample, which was synthesized by NaCl to NaClO3, then using metathesis double displacement to KClO3, burned yellow with traces of purple. This leads me to believe my second sample, the white sample, is mostly NaClO3 and alot did not crystallize to KClO3. I am sure I used enough KCl for the metathesis. What should I do now? Try to recrystallize it again? Should I make a saturated solution or the white crystals and then add KCl in again and try again to perform metathesis?

[Edited on 2-5-2013 by binaryclock]

woelen - 3-5-2013 at 12:52

The white stuff you have is most likely better than 99% KClO3, so you have a very pure product. This stuff is perfect for nearly all purposes, except for pyrotechnics in which you want nice flame colors.
Even 0.1% sodium ions in a pyrotechnic composition will completely spoil the color effects of the composition. Sodium ions give a very strong orange color to flames and the weak color of potassium is overwhelmed by this. If you start with NaCl, then it is hard to remove the last traces of sodium. If you intend to use the KClO3 for general chemistry experiments, then leave the white material as is and use the grey stuff for pyro experiments.
For pyro-purposes, purity of KClO3 is not really important as long as it does not contain any sodium ions and any organics or strong reductors. Your grey stuff is good enough. Of course, if you only want bangs or smoke, then the presence of some sodium is no problem.

Because of its high purity, it is of no use to add additional KCl to your white material. If you really want to get rid of the sodium in it, simply dissolve it in as little as possible of boiling water and then allow to cool down slowly. Decant the liquid from the crystals, rinse with distilled water (not tap water, because that also contains some sodium). It might be that you need multiple recrystallizations, leading to quite some losses. It probably is not worth the effort.

[Edited on 3-5-13 by woelen]

Manifest - 27-6-2013 at 15:24

So wait, what's the double metathesis method? Can somebody explain it in detail?

12AX7 - 27-6-2013 at 18:48

Double metathesis is where you take two ordinary salts, and, driven by precipitation, the ions trade partners. Example: CaCl2(aq) + Na2CO3(aq) --> CaCO3(s) + 2NaCl(aq). CaCO3 is highly insoluble and drops out of solution, while NaCl remains in solution. Filter it out, then evaporate the solvent to recover the NaCl. Now you have two solid compounds different from what you started with.

In this case, KClO3 is moderately soluble, and can be crystallized out of solution easily.

One more recrystallize-wash-dry cycle of that white KClO3 will probably remove the sodium impurity well enough for the pickiest users. Like I said earlier, I've made pyrotechnic grade KClO3 by metathesis without too much trouble.

Tim