I'm not a chemist - (College Chem101 in 1958). That's why I referenced the article - I'll see if I can find it again - might even be in the files in this group.
As I understand it, the etching is a conversion of metallic copper to copper chloride, which is soluble. Therefore, the free chlorine ion is required. I don't think the chlorine in the HCl is free to combine. The formation of the copper chloride is what turns the solution blue-green (also why ferrous chloride turns greenish as it is used).
Anyway, the HCl + H2O2 works for me, it's cheap, and just about inexhaustible (Bubble air through it - converts the CuCL to CuO (or some such) and releases the Cl ions for re-use. Adding the small amounts of H2O2 would also add the needed oxygen to regenerate the solution without the bubbles.
Again, not a chemist, but this is what I've read/experienced.
Norm
Thanks Norm.
Yeah, I’m just reluctant about using actual HCl for the reasons you mentioned. I’m generally pretty careful but I’m also a bit accident prone and I don’t want to wreck something, or myself, messing around with that kind of acid. I’ve accidentally splashed this vinegar/salt/peroxide solution on me and not even slight irritation. I’m sure that wouldn’t be the case with HCl.
What I’m curious about though is that supposedly the reaction will still work ∗without∗ salt.. just takes longer?
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