--- In
Homebrew_PCBs@yahoogroups.com, William Kroyer
<william.kroyer@...> wrote:
> CuCl can be regenerated. It already has copper in it to begin
> with. It seems to me that when etching you are actually just
> making more CuCl. ... I'm guessing it's "reguvinated" by
> simply adding more HCl or H2O2.
Yeah. See for instance here:
http://members.optusnet.com.au/~eseychell/PCB/etching_CuCl/index.html#operate_acid(or our own archives.)
The etch reaction is:
CuCl2 + Cu --> 2CuCl
Where CuCl2 is supposed to be bright green, and CuCl is brown muddy
stuff.
The "regeneration" reaction is:
CuCl + HCl + O --> CuCl2 + H2O
In my case the O is provided by bubbling air through the solution.
But the CuCl2 is supposed to be green, and the CuCl2 sorta brown and
borderline insoluble, so I'm at a loss as to how I got blue...
Dilute solution of CuOH, perhaps (this is normally pretty insoluble.)
I was hoping to avoid titration-like measurements, but perhaps this
is going to be impossible, basing replenishment on color, opacity,
and the fact that I though aeration-based replenishment would just
stop when it was done (and some free HCl isn't so bad), but I guess
I can also drive away all the HCl...
BillW