re: Oxalic Acid

["roger" <roger at spinn_net>]

Paul Sears wrote:

> Does anyone have a number for the standard electrode potential
> for oxalate/CO2?

I don't, but my old CRC Handbook gives the standard free energy of formation
for oxalate ion and CO2 as -161.3 kcal/mole and -92.31 kcal/mole,
respectively.  From that the standard free energy for the reduction of CO2 to
oxalate ion:

2(CO2) + 2e- -> 2(OOC-COO)-2

is +23.32 kcal/mole.  The corresponding standard reduction potential is +0.5
volts.

It seems to me (not having done this before) that the electrolysis will work
better with high oxalate concentrations and when the solution is buffered (as
Paul said) to a pH well above the second pKa for oxalic acid.

If you can get the reaction to produce CO2 at a usable rate then the next
problems are to make sure that it's pure enough to be useful and to pressurize
the gas enough to get it into the tank.

Good luck.  Either yeast and sugar or bottled gas seems much easier.


Roger Miller