G’day, Vira: You can dissolve gold in aqua regia, which is 4
parts of hydrochloric acid to 1 part of nitric acid; warming -
not boiling! helps, but it takes a while.
V> Also, I’ve wondered, when etching silver in nitric acid, can
V> that “lost” silver be reclaimed again?
Yes it can indeed. My wife, who was in charge of a 400 student
laboratory at a university reclaimed kilos of the metal, (large
amounts of silver nitrate are used in analytical chemistry.)
when the American, William Bunker Hunt attempted a ‘corner’ on
silver, and silver nitrate rose in price to $500 a 500 gram
bottle! She had all silver-containing solutions and precipitates
set aside, and precipitated silver as silver chloride by adding
common salt solution. (sodium chloride) She dissolved this in
potassium cyanide solution (about 5% - it isn’t important) and
using a car battery, passed an electric current through the
liquid with two bits of scrap stainless steel as electrodes.
Pure silver deposits on the negative electrode and may be easily
peeled off. In Jean’s case, she then re-dissolved the silver in
nitric acid and crystallised out the pure silver nitrate - back
where they started, ready for use in the labs again.
In your case, you could try passing the electric current through
the silver nitrate solution directly, though I’m not sure if it
would work: both silver and gold deposit best from cyanide
solutions. In the case of the auric (gold) chloride from the
acid aqua regia, you could neutralise the acid with caustic soda,
add a little sodium or potassium cyanide, and plate-off as
In the case of silver nitrate, you could neutralise that with
caustic soda or potash, add some cyanide and plate-off the pure
silver. But do NOT ADD CYANIDE TO ACIDS!! - it’s very bad for
your continued living! On the other hand, don’t be unduly afraid
of cyanide - just use common sense and be careful not to ingest
it or get any in a cut.
But don’t expect to get much gold from PC boards - it is a bare
flash, so little you can’t measure it easily without very
This is a statement of what can be done, Vira. If you want a
detailed plan of how to recover the metals, do email me
directly, telling me exactly what you start with. Finally, you
could etch your silver electrically anyway.
/ / John Burgess,
/ //\ @John_Burgess2
/ / \ \
/ (___) \