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Do i have to have certain metals to synthesize potassium perchlorate using electrolysis?

I know how to make potassium chlorate using electrolysis but I've seen on YouTube that you can use NaCl (table salt) in a mixture with water and that i can electrolyze it with platinum and titanium (or steel) electrodes. i need to get around shipping stuff to myself (because my parents) so i wanted to know if i should just make KClO3 or if  i can use two stainless steel electrodes or if there are other easy accessible metals i can use

I have read a lot about electrolysis cells used to produce chlorate ion, and it seems to me there are a number of problems to overcome to make a cell that actually works.

Starting this story from the beginning:  There are four different kinds of chlorine-oxygen ions, all consisting of 1 chlorine atom and n oxygen atoms.  In order of increasing n (and also increasing valence on the chlorine atom), these are:
  • hypochlorite ClO-
  • chlorite ClO2-
  • chlorate ClO3-
  • perchlorate ClO4-
This page,
http://en.wikipedia.org/wiki/Chlorite#Oxidation_states
has a little table with some nice pictures and data for those different ions.


Of course, the ion you want is chlorate, ClO3-,  and the usual recipe for making it is to bubble chlorine gas through warm water containing OH- ions, i.e. through a basic solution.  How warm, at what temperature? Well, the Wikipedia article on Chlorate ion, says 50 to 70 C, here:

http://en.wikipedia.org/wiki/Chlorate

Interestingly the same reactants, Cl2 gas and OH- ions,  in cold water, will make hypochlorite ion, ClO-
http://en.wikipedia.org/wiki/Hypochlorite

So I think getting the temperature right is the first challenging part. 

The next challenging part is what you were saying about the electrodes:  chlorine gas in warm water is corrosive to most metals. 

The first thing I would try is using carbon electrodes, like those harvested from a carbon-zinc battery, or from an old electrolysis type humidifier.  To  me that seems like the easiest thing to try.

The second thing I would try would be putting a regulator on the current supply, so that you can actually control the current density at the electrodes.  BTW current density (has units of ampere*cm^-2) is just the current in the circuit (in amperes) divided by the area of the electrode.

Also on the subject of control, it would be nice to have a thermostat on the whole cell, so you can actually keep it at the temperature at which the reaction is supposed to happen.

I mean you kinda have to know that's what the pros are doing. I mean the chemical engineering wizards that  actually make, and sell, chlorate on a large scale.  The parameters of their cells, current, temperature, pH, concentrations, etc, are all under tight control, so the reaction happens consistently, and optimally.

But the naive garage-based chemist would prefer to just stick some electrodes in a glass jar, and hook it up to a car battery, and just hope for the best:  Hope it warms up to the right temperature.  Hope the current density is not destroying the electrodes.

Anyway... I think your main question was about electrodes, and the choice of metal, or material, for this.  I have read lots of chatter on this subject.  The corrosion is worst at the anode, where the Cl2 gas appears, and I think the pros use titanium coated with other the oxides of other metals, like oxides of manganese, cobalt, iron, etc.

The reason for making an electrode with a special metal oxides layer was that naked titanium passivates when used as an anode; ie. it builds up a layer of TiO2, and that layer is an electrical insulator, and that stops the current.  In contrast, those other metal oxides are electrically conductive, at least in very thin layers.

I have also read rumor of lead, or lead-alloy electrodes. Guessing that those naturally develop a layer of conductive lead oxide on them, when used as an anode.

I seem to recall that NurdRage
https://www.instructables.com/member/NurdRage/
http://www.youtube.com/user/NurdRage?feature=watch
did some work, and videos, on the subject of making a mixed metal oxide (MMO) coated titanium electrode. 

Make Manganese Dioxide Electrodes (for chlorate or HHO cells)
http://www.youtube.com/watch?v=BjKYiu8eKa8

Make Manganese Dioxide Electrodes - Revisited
http://www.youtube.com/watch?v=nvMVlhBmv7M


To me that looked like a lot of work, but if that's the electrode you want, I guess that's the way to do it.  I'm not sure what it costs to actually buy such an electrode. I'm not sure if I want to know. ;-)

Anyway, like I was saying before, there are other things to try.  I suspect that cheap carbon electrodes will hold up, if you just go easy on the current density, and the way you do that is by making, or buying, a power supply that can supply constant current.  So you've got a knob you can turn to control current. 

A thermostat (via a heater or cooler) to make the cell temperature be just what you want it to be, that would be nice too. 

Another approach might be using a  cell with a separator, so that you could make Cl2 gas, and then pipe it to a separate reactor where it bubbles through base (OH- ions) to make your chlorate.

However, I think the regulator for electric current is the most important improvement you could make, and you should focus on that first.  I mean if you want to do it that way. 

Like I was saying before, I think most amateurs just build a cell, and plug it in, and then pray that it works, with no attempt at actually controlling the reaction parameters.
 





hopekiller30 (author)  Jack A Lopez4 years ago
well i definitely thank you for the extremely in depth answer you gave me but you answered actually other things about my question that i was absolutely oblivious to such as the temp. and the certain current needed. i have seen the project done with even two steel knives and 2 9volt batteries so i guess i will have to be that naive garage-based chemist that really doesn't know exactly what he is doing and i might just go ahead and do it with my computer power source and some knives in plastic jug and i might just defy the professionalism that is neccissary (and no i don't mean that as an insult to you or other smart or smarter chemists)
If your having to sneak this around your parents then maybe you shouldn't be doing it.

hopekiller30 (author)  mpilchfamily4 years ago
well now that i see the be nice statement under my comment that ruined my chances a totally disowning you. but the thing is is that i've put so much work into my home science projects that my parents would only be the slightest of skeptical if i purchased even a full lab set that contained the most eye-opening equipment so i just really don't care as to what you say about me and my ways around pyrotechnics and chemicals.