Homebrew PCBs

--- In Homebrew_PCBs@yahoogroups.com, DJ Delorie <dj@...> wrote:
>
> 
> "perri.anthony" <perri.anthony@...> writes:
> > So I mixed a solution of Muriatic Acid (1/2 cup) & Hydrogen Peroxide (1
> > Cup) to etch a board. It worked very well but now I am trying to figure
> > our how much baking soda it would take to neutralize that solution so it
> > can be safely disposed of.
> 
> A couple of things...
> 
> First, don't!  Keep the solution around and use it for other boards.
> Eventually it will turn a dark green and become copper chloride
> etchant, which doesn't "expire".  Note that this works if you're going
> to do it soon, else the peroxide breaks down and etching takes a lot
> longer.  If you leave it as-is for a while and want to re-use it, just
> add a little more acid and peroxide to "charge" it again.  Once
> there's enough copper in solution, you can recharge (regenerate) it
> with an air bubbler, then it's good pretty much forever.
> 
> Alternatively, add a bunch of copper to it now just to convert it.  I
> think I figured a half pound of copper per liter of HCl - you want the
> specific gravity (density) of the solution up to at least 1.2 for CuCl
> etchant (for details, see Adam's page at:
> http://members.optusnet.com.au/~eseychell/PCB/etching_CuCl/)
> 
> Second, the copper in solution acts as a pH guide.  It's green/brown
> in solution, but once the pH rises above 7 it precipitates out as a
> white milky fog.  This assumes you have enough in solution to see the
> change, though.
>
DJ Thanks for the feedback. If I decide to re-use it in the short term what are the precautions I need to be aware of for storage of the solution? The reason I was planning on neutralizing it was that it was so cheap to buy and readily available that I felt it wasn't worth the risk of storing it. Your thoughts?

Anthony