> I would not consider it immoral or illegal to dump small quantities
> of chemicals down the drain once I was told by local authorities
> that it's acceptable to do so

Living in a marine environment I wouldn't dump soluble copper down
the drain even if some desk-jockey at the local council said it was OK

At the very least I'd make it into a solid (eg drop the copper out with
sodium carbonate) as you suggest, and send that sludge to the tip.
Still not the ideal, and a tip shouldn't really be taken for granted and
expected to be an environmental basket-case. For the same reasons
I wouldn't send old lead or NiCd batteries out in the general rubbish

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