The production of copper hydrite in EIS is an interesting analytical
problem. The hydrate is rather unstable, and likely will react with
Silver hydroxide producing colloidal copper, colloidal silver and H2O.
If this is correct then using copper for the cathode would produce a
combination of both colloidal copper and silver. Then the colloidal
copper would likely react with silver oxide producing copper oxide, and
additional colloidal silver. Copper oxide is insoluble, and thus would
likely form a precipitant.
But I think the biggest problem with using copper as a cathode is that
copper will reduce silver hydroxide and silver oxide, so that the ionic
silver will plate out as silver on the copper, removing the silver from
solution as you are making it, reducing efficiency significantly. This
reaction can be confirmed by putting some copper into some EIS and
noting that it turns silver colored over time.
Marshall
Dan Nave wrote:
The cathode (in this case the negative terminal) can be copper if you
are not polarity switching.
The anode (in this case the positive terminal) must be silver.
You can see I don't agree with cking, as usual...
Dan
On Wed, Sep 8, 2010 at 5:28 PM, David AuBuchon <aubuchon.da...@gmail.com> wrote:
Is there any reason everyone uses silver for the cathode? I can understand
if people were reversing the polarity. But when things only go one way,
does it matter what the cathode is made of? Could it just be copper wire?
Also, isn't the surface area of the cathode important. With the anode, more
surface area reduces the density of a layer of silver ions coming off,
combining with hydroxide ions. At the cathode end, isn't there a dense
layer of hydroxide combining with incoming silver ions?
Thanks,
~David
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