Oxydro - 5-6-2005 at 16:44
When electrolysing NaCl, the Cl2(g) obtained is limited by the reaction with the NaOH formed at the cathode, correct? Note- I know that's
actually a simplification as it exists not as NaOH but as ions, but it's not relevant yet.
Now, this is very beneficial when making chlorates/hypochlorites depending on temperature...but say I want my chlorine gas. Then I have options. I can
do the mercury cathode thing making the amalgam and using water elsewhere to remove the sodium -- but Hg is not cheap or pleasant and large amounts
would be required. I can use a membrane or salt bridge of some description and that will help considerably. High current densities at the anode help
also, but with the side-effect of increased wear, no?
But I was wondering, how about bubbling CO2 gas into the solution. It would react, methinks, with the hydroxide, to form the bicarbonate, which is
much less soluble IIRC (7.8g/100ml). I don't know whether it reacts with chlorine - Help?
If desired, remove precipitate of sodium bicarbonate, and heat driving off CO2 and water to make the carbonate (decomposition begins at 60..) . In
turn this can be decomposed at temps unknown.
Am I stupid/crazy? I don't really understand chemistry well enough yet but to my mind what I think makes sense.
[Edited on 6-6-2005 by Oxydro]
12AX7 - 5-6-2005 at 19:05
Eh, "chlorine acid" (that is to say, Cl2 + H2O = HCl + HOCl) is stronger than CO2, period, and would keep it from proceeding, no?
Tim
Chlorine
MadHatter - 5-6-2005 at 22:31
Some Cl2 escapes even in my chlorate cell. That's inevitable. How do you intend to collect it ?
The small amounts that escape from my chlorate cell aren't deadly but are annoying as hell.
At the very least, any microbial bugs in my dwelling probably won't survive. 
[Edited on 6-6-2005 by MadHatter]
Oxydro - 6-6-2005 at 07:22
12AX7: the chlorine may indeed displace the CO2... but the idea is that chlorine is *probably* much less reactive with bicarbonate than hydroxide.
Also it reduces the concentration since it is much less soluble. Since the CO2 gas will be bubbled throughout the cell, hopefully most of the
hydroxide will be reacted before it has a chance to encounter Cl.
Hey, another thing I just thought of.... the carbon dioxide will also make the solution slightly acidic, greatly decreasing chlorine solubility, no?
MadHatter: I'll collect it similar to the Hoffman aparatus. Inevitably some will escape but I would imagine quite little. I've done this
before without any attempt to protect against the chlorates/hypochlorites and it worked well until OH concentration rose too high.
I suppose that my chlorine will be contaminated with carbon dioxide, but that's probably no great worry. I don't think it should interfere
with most applications.