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Whatever happens to pickle?

   You keep adding baking soda to the pickle until it stops
foaming up and then it is safe to flush down the toilet.  That
is, if you are talking about Sparex or something similar.

G’day; I use the same system, which In My Humble Opinion, is
reasonably safe and adequate. (nothing’s perfect) The pickle,
whether it is 10% sulphuric acid which I use, or strong Sparex, or
swimming pool pH reducer, is plain diluted sulphuric acid, or
sodium hydrogen sulphate,(sodium bisulphate, NaHSO4). When used
for sterling or lower carat gold the spent pickle will contain a
very small amount of copper, no gold and an infinitesimal amount of
silver (Silver sulphate is virtually insoluble in water or acid).

Baking soda is sodium bicarbonate (sodium hydrogen carbonate); it
reacts with sodium bisulphate to give sodium sulphate (Na2SO4)
which is more or less neutral. It reacts with the small amount of
copper sulphate (CuSO4) in the pickle to give copper carbonate,
(CuCO3) which is insoluble in water. There is a possibility that
the copper will re-dissolve in the sewage, which contains
ammonium-like compounds, but the amount you will cause to end up in
the sewage treatment plant will be swamped and highly diluted by
the rest of the stuff there. I doubt it would do much harm to the
environment even if every jeweller in New York emptied the pickle
pot (after neutralisation) down the toilet every night after work
is finished. He/she probably does.

Sewage contains just about anything you can imagine - and much
more you couldn’t imagine - and trying to guess what the end
product/s would be, is any chemist’s nightmare.

If you neutralised the pickle and evaporated it to dryness, then
chucked the stuff in the rubbish tin, it could still be broken
down at the tip. You could dig a hole and bury it if you’re really
worried, but there’s so little toxic copper there it wouldn’t do
much harm - unless you dug it up and ate the soil… Of course,
you could heat the residue strongly after neutralisation, when the
copper would become copper oxide; only to be slowly attacked by the
carbonic acid in rain … So, I’ll leave my NZ$0.01 worth at
that. With Cheers,

   / /    John Burgess, Nelson, New Zealand
  / /
 / //\    @John_Burgess2
/ / \ \

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