Sciencemadness Discussion Board

Potassium Chlorate electrolysis

AmicableTerror - 17-9-2014 at 17:38

Hey guys! I am planning on making some potassium chlorate from KCl I obtained. I have a modified 350 watt computer power supply and practically as much KCl as I would need. For electrodes, I have graphite (That's pretty much it, I don't feel like buying MMO electrodes or some variant). To my current knowledge the graphite will contaminate the chlorate but I should be able to remove it by filtration of a hot solution. I don't have any plans for PH control but I could probably set something up. I was wondering what sort of set ups you guys have used in the past for this process. I don't plan on making very much and the reactor won't need to be bigger than 500ml.

Amos - 17-9-2014 at 17:52

Potassium chlorate is a pretty hot topic on this site. There are loads of threads already dedicated to it, so I'd advise you to simply use the search engine. That's what it's there for. Welcome to sciencemadess!

[Edited on 9-18-2014 by No Tears Only Dreams Now]

Zyklon-A - 18-9-2014 at 05:59

This is how I interpreted you post:
Quote: Originally posted by AmicableTerror  
Hey guys! I want to build a chlorate cell. I don't have any questions, just thought I'd post this. I don't want to spend any money on anything that might make it work, just want to use crap that will contaminate my product, and be a pain in the ass to purify. I don't want to elaborate on the voltage or amperage I intend on using, or what materials I will use for the electrodes (other than graphite). I can't buy a $1.50 pH testing paper kit, and I won't be using chromates to increase yields. I don't want to post this in an existing thread, because then people would just point out that all my questions are already answered further up.
I measure my intended quantity of chlorate in terms of mLs.

My answer: Don't use carbon. They are never satisfactory in the long-run. I can sell you some MMO for $3.00/sq inch if you live in the US. Find a way to measure the pH. I can include a few grams of potassium dichromate with the anodes if you want - they increase the yields and rapidity of the reaction. Use 4-7 volts and about 1 amp/50 mLs of solution. Electrolize sodium chloride to chlorate, boil, then add potassium chloride to precipitate potassium chlorate - this work much better than electrolizing potassium chloride to begin with. Use PVC for the vessel.
Read this:

Attachment: Production_of_Potassium_Perchlorate (1).pdf (673kB)
This file has been downloaded 629 times

[EDIT] Whoops! Uploaded the wrong file...

I am not on my computer ATM, and thus can't find what I was looking for:(. You might as well read the PDF on perchlorates too though. There are plenty of sites with good details on the subject: My favorite Some others: http://www.utahpyro.org/compositions/PreparingChlorates.pdf
http://www.dtic.mil/dtic/tr/fulltext/u2/242192.pdf

[Edited on 18-9-2014 by Zyklon-A]

AmicableTerror - 18-9-2014 at 20:16

Firstly, thank you for the help despite the confusing post. Looking at it, my post really does look pretty stupid, so allow me to explain what I was trying to do better. I plan on using the 5v output from a modified 350w computer power supply which is marked at around 22A. I do have pH paper to test, but I was thinking I would need something like this. I don't know where you decided that I was measuring chlorate in mL, but to repeat myself; I don't need a reaction vessel larger than about half a litre as I do not plan on making large amounts. My original purpose was to see what other people had set up themselves, because searching for chlorate electrolysis/potassium chlorate/chlorate production or similar things, I only found people either mentioning them offhandedly or talking about how many threads there are about them. I could not, however, find these threads myself (Because I hadn't been going exclusively by post title, they are pretty easy to find with that however). I have already looked at the woelen guide which is also probably the best source of that information that I have found. Again, sorry for the low quality post, hope this clears things up.

Zyklon-A - 18-9-2014 at 20:31

Not a problem. Just a note about pH paper, you can't just test the solution by putting it in there. It will bleach the paper, and the measurement will be way off. First boil a small sample for 2-5 minutes to disproportionate the sodium hypochlorite to chlorate, then test that.
As for mLs, that was a mistake on my part. Have a good one.
[EDIT] BTW, MMO isn't just useful because it's inert, the ruthium oxide(s) is very catalyticly active in the formation of chlorates, hence the reason it's used industrially rather than cheaper inert anodes like manganese dioxide and such.
Also, you are using the amount of power my cell uses (5 volts and 20-22 amps). My cell works fine and runs nearly constantly. I have never had to replace the anode in the 5 months I've used it. It is running as I type.

[Edited on 19-9-2014 by Zyklon-A]

AmicableTerror - 18-9-2014 at 20:45

Thanks for being so helpful! In regards to the electrodes, you said that it would be a pain to remove the graphite bits from the solution if I used it as an electrode. Would filtering a solution in which the chlorate was completely dissolved not do this? I don't doubt that an mmo electrode would be nicer, but would graphite or stainless steel work as well? Also, is the potassium dichromate worth the extra efficiency? Like I said, I won't be running this a whole lot and unless there are vendors selling potassium dichromate on the scale of <=1g or I can find other uses for it then I don't see it as being very worthwhile to get.

Zyklon-A - 18-9-2014 at 21:03

Depending on the quality of you graphite, the carbon might filter easily. However, it does decrease yeilds as it can reduce chlorine to carbon tetrachloride, four moles of chlorine are waisted for every mole of carbon oxidized, chlorine that should become chlorate.
Also, time is waisted every time you need to filter it, and time is waisted every time you change the anode.
Stainless will not work at all, it will dissolve rapidly, forming toxic nickel and chromium salts, which are much harder to separate that carbon partials.
Whether dichromates are worth it us up to you, they prevent reduced ions from being oxidized, and oxidized ion from being reduced as they travel from one electrode to the other IIRC.
You won't be able to buy just a gram of it, but I can give you a few grams if you buy an anode.

barbs09 - 18-9-2014 at 21:20

Hi Zyklon-A, was not aware that the electrolysis of NaCl to chlorate was more advantageous than that of starting of with the direct conversion of KCL to KClO3. I assumed that this would be a function of solubilities, but studying relevant solubility curves, at cell operating temps, there isn't much difference between the two salts. Given the extra step of double decomposition to obtain potassium chlorate, is starting off with NaCl really that more efficient for the small time DIY-er? Cheers, AB

woelen - 18-9-2014 at 22:39

Here is a writeup of making a small cell. It is quite successful. I work immediately from KCl, it works very well and you do not have the issue of Na-contamination if you want to use it for flame-coloring pyrotechnic compositions.

http://woelen.homescience.net/science/chem/exps/miniature_ch...

I would say, seriously consider Zyklon-A's offer for MMO and having a few grams of K2Cr2O7 at hand also is useful. Of the latter you only need a little amount, a few grams is enough for several liters of electrolyte.

[Edited on 19-9-14 by woelen]

Zyklon-A - 19-9-2014 at 06:08

barbs, I'm not sure how much of an advantage NaCl has over KCl. One reason is that sodium chlorate has a much higher solubility than that of potassium, so the cell can run much longer by adding more NaCl. The reason I do it has more to due with my lack of KCl. I have less than 100 grams now, because I used most of it.
BTW, does anyone know weather K2CO3 would work to precipitate KClO3 from NaClO3?

Amos - 19-9-2014 at 06:16

I can't answer your question about the potassium carbonate right now, but if you're in this for the long haul, I can provide you a couple of options. The first one is just to make potassium chloride from the carbonate if you have to. As far as obtaining cheap potassium chloride goes, you can look for sodium-free water purification tablets at a hardware store. It's astoundingly cheap when bought this way, something like $20 for 40 lbs(and they'll ship it to the store too). Most people buy salt substitute over and over because they don't need a whole 40 lbs or they don't know about the option, but I think having too much KCl is better than spending the same amount for 2 pounds or so. Again, if you already knew this was an option, my bad.

macckone - 19-9-2014 at 06:25

Quote: Originally posted by Zyklon-A  
barbs, I'm not sure how much of an advantage NaCl has over KCl. One reason is that sodium chlorate has a much higher solubility than that of potassium, so the cell can run much longer by adding more NaCl. The reason I do it has more to due with my lack of KCl. I have less than 100 grams now, because I used most of it.
BTW, does anyone know weather K2CO3 would work to precipitate KClO3 from NaClO3?

No the carbonate is relatively low solubility.
Use HCl on the carbonate and crystallize
Or buy salt substitute and clean it then crystallize.