[Sturmcrow]

I have been trying to convert chloride to perchlorate for about 6 months.  I'm working at a 50mM level, while most of the literature I can find deals with saturated solutions.  After months of optimization I have settled on a platinum anode and stainless steel cathode.  I'm running the cell at 40 mA for one day and then boosting it to 100 mA.  The potential varies, but is around 3V.  I increase the pH to around 11 with NaOH, though I have not been buffering it.  I've gotten 60% yield once, and have not been able to duplicate it.  The electrochem prof. at my university suggests that I was pretty lucky to get a value that high.

I get 100% conversion of the chloride to chlorate overnight, but then the synthesis stalls and I typically max out at 40% yield.  I have started trying to drive the oxidation further with chemical oxidants.  Ammonium persulfate was ineffective and I am trying potassium permanganate as I type this.  The chemistry is performed in a boiling water bath inside sealed vials.

I suspect that my problem is that I am preferencially oxidizing water and that none of my current is going towards the chlorate.

Any suggestions are appreciated, even if they seem inconsequential to you.  I'm more a civil engineer by training with a microbiology focus during my phd, so chemistry is not second nature to me.

[408]

Concentration way way too low
voltage too low

http://www.wfvisser.dds.nl/EN/perchlorate_EN.html

[Sturmcrow]

Concentration way way too low
voltage too low

http://www.wfvisser.dds.nl/EN/perchlorate_EN.html

Unfortunately, the concentration is what it is.  I forgot to mention before, but the reason I am doing this is to synthesize radiolabeled perchlorate which, so far as I know, cannot be bought and must be made from radiolabeled chloride.  I've got 5mg of chloride to work with and have to make the best of it.  I could raise the potential, but I'm not sure it is necessary.  The standard potential for chlorate to perchlorate is only 1.226 V, so 3V should be more than high enough to drive the reaction.  Assuming I did my Nernst eqn. correctly, 3V should lead to an equilibrium perchlorate concentration something like 10^30 higher than the chlorate concentration.