Okay, so after being inspired by seeing a video of an NaCl electrolysis unit on Youtube utilizing a meager cardboard cell separator for making lye on
the cathode side, I believe I have an even better idea:
Using a coffee pot as a cell container, a steel or stainless steel large diameter but short pipe segment as a cathode, a clay flower pot as a cell
divider, and either a lead or graphite anode inside the flower pot (I was picturing lead flashing wrapped around a glass beer bottle), and using
Na2SO4 as the electrolyte, a better means of producing hydroxide might be had.
Also, on the cathode side of the cell, there would be CaSO4 * 2H2O suspended in the Na2SO4 electrolyte, meanwhile there would be CaCO3 suspended in
the Na2SO4 within the anode compartment (flower pot).
As the sodium ions are reduced at the steel cathode to form NaOH, they would eventually react with the CaSO4 * 2H2O to form insoluble Ca(OH)2:
2NaOH + CaSO4 ---> Na2SO4 + Ca(OH)2
At the anode side, H2SO4 formed would react with the CaCO3 to form insoluble CaSO4 (and possibly bisulfate of Ca too):
H2SO4 + CaCO3 ---> CaSO4 + H20 + CO2
Obviously, magnetic stirring would probably be beneficial in promoting these reactions.
Although the flower pot would impede the current flow greatly, it would work well to prevent the final products from mixing, and the insoluble
precipitates would act also to help keep the products separated.
Upon completion of running the cell, the Ca(OH)2 which should have precipitated on the cathode side could then be filtered, washed with DH20, and then
reacted with washing soda to form lye:
Ca(OH)2 + Na2CO3 ---> 2NaOH + CaCO3
Now the lye could be isolated in solution via simple filtration.
Although this is quite a round about method, the great thing about it would be that no chlorine fumes are produced making it much safer, a lead anode
could be used (since the electrolyte is a sulfate salt), and the end products should be much easier to segregate. Also, this method utilizes
ridiculously simple to obtain ingredients, such as plaster of paris and baking or washing soda.
[Edited on 10-12-2012 by chemicalmixer]hissingnoise - 10-12-2012 at 11:19
Quote:
Ca(OH)2 + Na2CO3 ---> 2NaOH + CaCO3
Slaked lime and washing soda ─ pretty circuitous, if not totally unrealistic route to those simple reactants . . . ?
And a slow and incomplete metathesis, to boot!
I'd just buy lye(oops!)!
Failing that, I'd use ordinary builder's lime and my 'better half' uses ordinary WS . . . a lot!
