Sergio,
Thanks,
And thanks again for "making" me do the experiment to prove myself wrong=20
about simple dropping out the copper with bicarb - don't want to spread=20
false info.
but I have found the trick to get the last tiny bit of copper out of=20
solution. The Baking soda neutralized solution has all but a trace of=20
the copper precipitated out of it but there is still a faint blue tint.=20
A bit of fine steel wool dropped into this solution removes this last=20
trace of copper to the point that even ammonia won't make it turn blue=20
(this is a pretty sensitive test for copper).

By the way, muriatic acid is an entity that is bought at the hardware=20
store, so needs no concentration figures. BUT, my bottle does say 20=20
degree Baume (whatever that means) also says (31.45%)
I CAN attest that the 2 parts drugstore H2O2 to 1 part hardware store=20
muriatic acid makes a fine pc board etchant - I used a fine brush to=20
"agitate" the etching and it took around 5 minutes.
One beauty of this system is that the H2O2 is less than $1.00 and my=20
muriatic acid label says $2.99 (1 quart) (bought within the last couple=20
of years)
I would NOT guess that concrete cleaner would necessarily be the same=20
stuff even though muriatic acid IS used for that purpose.
Evaporating to dryness is fine if you don't have much solution, and live=20
in a low humidity place, and are patient, and have the spare space where=20
it won't be disturbed by wives or animals (I have both - well, only one=20
of each). At least it does not have acid fumes after neutralizing so the=20
evaporation can be done inside.


"
Hi Al,
Might I suggest that you simply let the neutralized solution evaporate=20
to leave just solid then dispose of all the solid together (possibly=20
together with other metal that is to be recycled).

Regards
Sergio Masci
"
--=20

Looking forward,
Al Shinn

--=20
http://www.piclist.com PIC/SX FAQ & list archive
View/change your membership options at
http://mailman.mit.edu/mailman/listinfo/piclist
.