The usual recipies are designed for one part 37% acid and two parts 2%
peroxide. Since you're using a weaker acid and a stronger peroxide,
you'll have to figure out the new ratios, but it will probably end up
being two parts acid to one part peroxide. Never add peroxide to acid!
Always add acid to peroxide.
You don't need to worry about the chemistry until it stops etching :-)
But note: the peroxide breaks down over time, so make enough solution to
use in a week or two. You can always grow more solution later.
http://www.instructables.com/id/Stop-using-Ferric-Chloride-etchant!--A-better-etc/
http://members.optusnet.com.au/~eseychell/PCB/etching_CuCl/If you want to skip right to CuCl, I found that about half a pound of
copper converts 3 liters of CuCl etchant.