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Re: Carbon dioxide generation by electrolysis of oxalic acid

> From: Denis Daly <dalymob at bigpond_com>
> Subject: Carbon dioxide generation by "electrolysis?" of Oxalic acid (ethanedioic acid)
> A friend seen a CO2 generator in a hydroponics shop that was
> supposed to work on electrolysis of Oxalic acid.

	In priciple, this could work O.K..

	-OOCCOO-  ->  2CO2 + 2e-     Anode reaction
	2H+  +  2e-  ->  H2          Cathode reaction

	I haven't been able to find the standard electrode potential
for the anode reaction, so I don't know how well it would proceed
in competition with the other possibility:

	4OH-  ->  2H2O  +  O2  +  4e-

	Keeping the pH low would help, as would keeping the oxalate
concentration high.

> The salesman trying to sell my friend the commercial product
> claimed that it could be turned on and off by turning on or off
> the DC supply to the electrolysis cell.

	That is how it would work.
> Has anyone got any ideas of what the catalyst could be,

	I would start with sulphuric acid, to keep the pH low and 
hence the OH- concentration _very_ low.  Don't use hydrochloric acid -
you would get undesirable anode reactions.

> optimal
> cell voltage (I could find that by using a variable power supply)

	It will be only a very few volts.

> and whether stainless steel would be suitable for the anode and
> cathode.


	As mentioned by someone else, oxalic acid is very toxic, and
not to be handled carelessly.

Paul Sears        Ottawa, Canada