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Retrieving silver from a nitric acid bath


#1

I am dissolving a lot of silver in a 2:1 / water : nitric acid bath.
How does someone go about getting the dissolved silver back from a
nitric acid bath?

Is this a process that requires a lab?

I’m not familiar with ferric chloride. Does the etched silver just
settle to the bottom or does that also dissolve?

I’m not etching gold yet, but for future reference… How does
someone retrieve gold from an acid bath?

Thank you Cynthia for your response in my last etching question.

kerri


#2

I’ve never actually done it, but the book way that I learned when I
did a little etching is to pour a solution of sodium chloride (table
salt) into it. What happens chemically is that you create silver
nitrate when you etch Ag+HNO3->H2+2(AgNO3). Silver Nitrate is
readily soluble in water. When you add Sodium Chloride, the silver
and the chloride combine - chloride will “grab” the silver away from
nitrate. Silver Chloride is insoluble in water, and will precipitate
out as a white powder. Pour it through a coffee filter, and
apparently when you melt it it will decompose and you’ll get a
button of silver. This is out of a book or chapter about etching.
Even if the melting isn’t feasable, the precipitate contains your
silver…


#3

Kerri,

I’m making mys suggestion based on first principles learned in 1st
year chem.

Are you using concentrated nitric acid? If so, I sincerely hope that
your are wearing eye protection when pouring it, because a splash in
yours eyes will cause permanent eye damage.

The Handbook of Chemistry and Physics does not include nitric acid
as a solvent for for AgCl. So my first approach would be to add
table salt(NaCl) to the acid bath, and since AgCl is very insoluble
in water, adding the salt should create AgCl. If the pickle is too
acid and nothing comes out of solution, I would then add baking
soda, Na2CO3, to buffer the acidity. Be careful, because a
considerable amount of CO2 will come off as a messy foam.

Finally I would ask myself if it is worth the effort. How many
milligrams of silver are in solution? Let’s imagine that is 1000mg,
and let’s say for the sake of argument that silver is costing around
$7.00 for 31 grams. All your effort would yield about $0.23. I
suspect that you will spend more than that to neutralize the pickle.

David


#4
I've never actually done it, but the book way that I learned when
I did a little etching is to pour a solution of sodium chloride
(table salt) into it. 

This works BUT DO NOT TRY TO MELT THE SILVER CHLORIDE, unless you
have a laboratory fume hood to do it in. The chlorine gas that is
liberated will cause you severe respiratory problems and could even
kill you if you got enough in your lungs. I read about this
technique 20 years ago and tried it and it damn near put me in the
hospital and I had a ventilated soldering station where I tried it!
Send the silver chloride to a refiner and have them deal with it in
the proper setting.

Jim

James Binnion
@James_Binnion
James Binnion Metal Arts


360-756-6550


#5

David,

Finally I would ask myself if it is worth the effort. How many
milligrams of silver are in solution? Let's imagine that is
1000mg, and let's say for the sake of argument that silver is
costing around $7.00 for 31 grams. All your effort would yield
about $0.23. I suspect that you will spend more than that to
neutralize the pickle.

Good point. I will have to see how long my first bath lasts and how
much silver is lost in there. I am losing a lot of metal though. My
etching process is taking the place of my piercing, where the acid
is biting through my whole plate to cut out my shapes. And yes I use
a respirator, gloves and eye protection when needed because my bath
is a strong 2:1 mixture.

Thanks
Kerri


#6
Finally I would ask myself if it is worth the effort. How many
milligrams of silver are in solution? Let's imagine that is 1000mg,
and let's say for the sake of argument that silver is costing
around $7.00 for 31 grams. All your effort would yield about $0.23.
I suspect that you will spend more than that to neutralize the
pickle.

Hi

In the old days, in the eighties in South Africa, one of the main
occupations of a self-employed goldsmith was to stay one jump ahead
of the gold cops. I don’t know what the current situation is now, but
then they used to harass you endlessly. Filling in a stupid register
EVERYTIME one melted, weighing all your different golds at the end of
each day. Three warnings if your register was not up to date and then
a fine and possible jail.—because of your own gold. Having to get a
bank guaranteed cheque before you could buy gold, (no cash allowed)
and then being escorted into the Mint by an armed guard, to buy your
measly 30grams of fine. I always laughed at the irony-- the Mint
makes the money, but you got to bring a bank guaranteed cheque to buy
there. Made life a real hassle and that wasn’t the endless surprise
inspections of your records, safe or invoice books. I won’t even talk
about the 35% customs and excise duty that was enforced by the demons
of hell in another one of Satan’s departments. There were many times
when Sgt. De Beer (his real name) insolently flicked his fat ugly
thumb through my register, his red alcohol flushed face becoming
redder and redder because of some small mistake. At those times my
thoughts were anything but Christian.

Anyway, I am coming to the point.

I used to put all my yellow gold scrap, which consisted of 9ct and
18ct " old gold" and melt 5 times the weight of copper with it. So
100grams gold became 500grams gold/copper. Then I used to roll it out
into strips (which would supply me with my monthly gym work-out)
After that, I would dump the strips into concentrated Nitric acid.
This was done at home and at night, because of Satan’s sidekick, Sgt.
de Beer. After the reaction was finished I would be left with what
looks exactly likes coffee grounds. Dark brown and powdery. I used to
store small amounts in a Nescafe coffee jar, for workshop use. The
balance would be stored openly in the copper/gold form in my
workshop. They cops never did figure it out. It looks just like
copper. Or coffee-- and yes, before you ask, one of my workshop girls
did use it to make coffee once, but after she was told that that’s
the boss’ ‘private’ bottle of coffee, it was left alone. All I would
do is take a small amount of “coffee” and mix it with boric acid,
some saltpetre, and methylated spirits, to stop it flying around in
the crucible. When it was melted it would be regarded as 23c.t gold
and I would alloy it down to the proper caratage I needed. I would
also make my own solders from that fine gold, because the cops had
figured if you buy a lot of solder under permit and not much fine
gold, something did not balance. And 'knock knock", they would be on
your doorstep. I once tried to remove the silver out of the expended
nitric by adding table salt and the drying the white gunk that forms.
And them melting it down. Don’t bother. Was a nightmare, thick clouds
of awful white smoke and a tiny silver ball left. I used more oxygen
and gas and time than the silver was worth. If memory serves me
correctly, the white gunk also went grey where light fell on it and
stayed white in darkness. Like photo stuff.

Hans Meevis
http://www.meevis.com