dischem
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MMO anode degradation
Hey all,
I recently ordered a MMO mesh anode for chlorate production. It's got quite a bit of surface area, so I'm planning on taking advantage of that and
setting up a fairly large scale chlorate cell (roommate wants to make a rocket fuel...). I know 5v is usually used for chlorate cells to prevent
damage to the anode. However, I'm using an old ATX power supply that's rated for a higher amperage on the 12v rail than on the 5v rail.
My question is, is damage to the anode caused by overvoltage, too high of a current density, or both? I read somewhere (I'll find it later, on my
phone) that MMO electrodes shouldn't be used at a current density greater than 0.2 A/cm^2. Can I use the 12v rail on my power supply as long as the
current doesn't exceed 0.2A/cm^2, or will higher voltages damage the anode regardless of current density?
Many thanks
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Bert
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Before getting to the issues of electrode parameters, tell room mate he really wants perchlorates for rocket fuel? Chlorate is better as an oxidizer
for an explosive or pyrotechnic colored stars, it tends to make overly sensitive propellant.
Your over voltage power supply output is perhaps a resource for conversion of the chlorate from first reaction to perchlorate?
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Zyklon-A
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Using over 7 volts tends to make perchlorate rather than chlorate, which inevitably corrodes MMO.
I suggest using something to lower the voltage to 4-7 volts or else buy a Pt anode and make perchlorate.
And like Bert said, you don't want a chlorate based rocket - they tend to explode!
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Brain&Force
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Also, you can't make potassium perchlorate through electrolysis of potassium chloride - potassium chlorate tends to crystallize, preventing conversion
to perchlorate. You have to make sodium perchlorate and then precipitate it with a potassium salt if you want potassium perchlorate.
At the end of the day, simulating atoms doesn't beat working with the real things...
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dischem
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Well, rockets would be cool, but honestly he and I just want to make something cool that's cheap to produce. We were planning on just using chlorate
and sugar to keep the reaction relatively mild. If it does end up exploding...that works too. :-P
As brain&force mentioned, since the potassium chlorate precipitates out, could I use a higher voltage, or would there still be degradation at the
anode? The real thing I'm trying to understand is the mechanism which damages the anode. Overvoltage, or over current.
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Zyklon-A
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Well, both I think. Over current shouldn't be a problem though right, cause you said you have a big piece of MMO.
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MrHomeScientist
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Not if it's in your hand at the time!
I am not an expert in electrolysis at all, but what I've heard around here suggests it's excess voltage that is the killer. I still don't fully
understand why everyone wants to make boatloads of chlorate. So many threads on chlorate production, but almost no threads on chlorate use.
Pyrotechnics, or as a feedstock to perchlorate I suppose?
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Mailinmypocket
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It's sort of fun to run a cell you made and can operate. At least for me it is. Do a few runs and although it's more than I need for my uses, it is
cool to have around for campfires, making demos for friends outdoors etc. For the chemistry I do I rarely use it though.
Edit- I have used it as an exceptionally effective weed killer actually!
[Edited on 5-8-2014 by Mailinmypocket]
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MrHomeScientist
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Hah! That's pretty interesting. Massage finely ground chlorate into leaves and ignite? 
[Edited on 8-5-2014 by MrHomeScientist]
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Mailinmypocket
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Lol not that spectacular! It was something like a 10% solution poured on the base of the plant. They wither and die pretty fast within a few hours,
never bothered to read why though.
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Manifest
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I have made chlorate rockets before but I haven't 'cooked' it with sugar, for obvious reasons.
It worked as well as KNO3.
Do not ram the Chlorate/Sugar into the rocket tube or it may explode.
I have done hammer tests with Chlorate/sugar and it's hard to get it to detonate but it certainly does.
On topic, remember to keep the pH low to minimise corrosion of the anode, the best way to do this is with Sodium Bisulfate.
[Edited on 5-8-2014 by Manifest]
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Bert
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Sodium chlorate/Sugar is too touchy for casual propellant use by the inexperienced. It had a reputation for maiming and killing those who thought to
use it in pipe bombs & etc. in the various countries where Sodium chlorate was freely available as a weed killer.
Potassium chlorate + nearly any organic fuel + Sulfur has killed fire workers and powder hands a-plenty, starting with the very first people who tried
to harness the improvement in specific impulse over Potassium nitrate oxidized mixtures and created chlorate based black powder analogues.
Rapopart’s Rules for critical commentary:
1. Attempt to re-express your target’s position so clearly, vividly and fairly that your target says: “Thanks, I wish I’d thought of putting it
that way.”
2. List any points of agreement (especially if they are not matters of general or widespread agreement).
3. Mention anything you have learned from your target.
4. Only then are you permitted to say so much as a word of rebuttal or criticism.
Anatol Rapoport was a Russian-born American mathematical psychologist (1911-2007).
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hyfalcon
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Quote: Originally posted by Brain&Force  | | Also, you can't make potassium perchlorate through electrolysis of potassium chloride - potassium chlorate tends to crystallize, preventing conversion
to perchlorate. You have to make sodium perchlorate and then precipitate it with a potassium salt if you want potassium perchlorate.
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Strange, I didn't have any trouble with perchlorates, but I was using a platinized titanium anode in a small vessel running a 12v battery charger.
Temperatures stayed upwards of 65C keeping my chlorate in solution.
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dischem
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Huh, I didn't realize it was that touchy, thanks for the info. I've seen fairly mild reactions with sugar on YouTube, but I imagine the reaction
changes when compacted into a smaller space.
Thanks for the info on all this, very useful.
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arkoma
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I remember barrels of sodium chlorate solution in the farm shop in Arkansas. We sprayed it on soybeans and rice about a week before harvest as a
"dessicant". Helps deal with green bean syndrome in soybeans.
Whatever it does to plants to kill/dry them, it does WELL.
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gdflp
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Yeah when I tried a mix of potassium chlorate and sugar in a pyrex test tube, the bottom of the tube shattered in about two seconds. I wouldn't call
that mild
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dischem
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| Quote: Originally posted by gdflp | | Yeah when I tried a mix of potassium chlorate and sugar in a pyrex test tube, the bottom of the tube shattered in about two seconds. I wouldn't call
that mild |
Damn, 2 seconds after heating it up? It didn't just spontaneously explode did it?
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Zyklon-A
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| Quote: Originally posted by dischem | Huh, I didn't realize it was that touchy, thanks for the info. I've seen fairly mild reactions with sugar on YouTube, but I imagine the reaction
changes when compacted into a smaller space.
Thanks for the info on all this, very useful. |
Well, yes. It generally depends on quantity and confinement. If you have a five gram mixture and light it in the open, chances are it will just burn
quickly, but if you pound three hundred grams into a rocket motor, it might explode while pounding, or it might explode when lit, either way it's
quite dangerous.
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dischem
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Just an update, there's a ton of useful information I found here.
http://www.oocities.org/capecanaveral/Campus/5361/chlorate/c...
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jock88
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That page is now at this address
http://oxidizing.typhoonguitars.com/
[Edited on 12-8-2014 by jock88]
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