I was at a garage sale the other day and old fellow had a jewellers
torch for sale. We got talking and he said are you interested in
buying some silver. Thinking had some sheet or wire I said sure. What
he brought out were quite a few bars of very rough silver coloured
material.
Apparently he melted these down from solution that he got from an
Xray lab years ago.
My question is, what would the silver content be and are they worth
buying? Could the silver used for casting?
Thanks
Gerry
They are almost pure silver. The solution (guessing here) was
probably silver nitrate, recovered either from the developing
solution, or stripped off of the x-ray sheets. When I was doing
chemical photography, it was common to see advertisements for people
purchasing used developer for the express purpose of stripping out
the accumulated silver nitrate. At the very least they are worth
processing for scrap from a refiner.
That’s photographic reclaimed silver, it’ll be near pure silver
(there might be traces of other photographic chemicals, but if it’s
been melted down the purity will be @99% or better.
Yes you can cast it, treat it like fine silver, but I’d buy an
alloying package and make it into sterling silver (casts better and
the public seems to understand SS more as a jewellery metal).
Definitely worth buying IMO, if you want I can chip in some cash,
but I’m on the other side of the world so…
Thomas.
If you take old Xrays, and put them thru photo fix or rapid fix,
leave them in the tank for a while, then filter the used soultion
thru coffee filters you will find silver in the filter.
Jerry
That's photographic reclaimed silver, it'll be near pure silver (there might be traces of other photographic chemicals, but if it's been melted down the purity will be @99% or better.
I had used sterling from someone who used reclaimed photographic
silver, and one batch was contaminated and I had 9 3"x7" flasks with
250-350 grams per fla= sk that I cast, the metal was as brittle as
dry
pasta, pieces did not bend, they were so brittle they broke. One bad
experience in several years, but it was a horrible experience and a
loss of much time and money. Do a trial. or just refine it, it ain’t
that expensive.
Richard Hart
Just refine it, it ain't that expensive.
It’s also quite easy to refine (properly!) silver oneself.
It does happen, I never said it was perfect option; contamination is
always a possibility when you alloy your own metals.
If I were to go this way, and I have in the past, I would buy an
alloying mix from a reputable supplier (eg H&S), and make sure that
the silver (or gold) is as pure as you can get it. For silver
dissolve it in nitric acid and precipitate out the silver with
copper. The result should be 99.9% pure silver (or better if your
silver was really clean prior dissolution as well as the copper (use
pure copper and it should be bright and shiny clean too)).
I’ll leave the topic of gold alone!
But the easiest option is to send the silver to a refiner and get
them to send back the equivalent in SS casting shot or what ever.
Thomas.
Hi Thomas,
For silver dissolve it in nitric acid and precipitate out the silver with copper. The result should be 99.9% pure silver (or better if your silver was really clean prior dissolution as well as the copper (use pure copper and it should be bright and shiny clean too)).
Would you expand a bit on how to precipitate the silver out of
solution with copper? Dissolving in nitric acid is simple enough. (
and I understand the precautions necessary, toxic fumes, etc.) After
the silver is in solution,in addition to the copper alloy already in
the silver, how do you proceed to precipitate out the silver, and
clean and reduce to pure metal?
Thank you
The silver solution should be filtered and then dried (so you have
silver nitrate crystals, wash these with ethanol (anhydrous is best,
but 96% denatured/methylated spirits will work quite well) on filter
paper so you don’t loose any crystals, all this should be done with
care and in dim light as silver nitrate is somewhat unstable (on
where near as unstable/sensitive as silver halides).
Dissolve the silver nitrate in distilled water until you have a
saturated solution at room temperature. To precipitate the silver add
metallic copper (pure copper wire/strips what ever), the silver will
come out of solution as metallic crystals on the copper, as this
happens the solution will turn blue.
When the solution is free of silver crystals will stop forming.
Drain the spent solution of the copper/silver mass wash and dry the
silver. You now have PURE 99.99% silver (if you were even just
reasonably careful the purity will be 99.9%). You could push the
purity a bit further by repeating the process, but unless you need
five nines silver don’t bother. You are now ready to add the alloying
metals to make some new sterling (or what ever) silver.
I did this for fun when I was 14 or 15 years old, there is on way
that a kid that old could get the acid required today. Oh well.
Thomas.
Dear Ag,
how do you proceed to precipitate out the silver, and clean and reduce to pure metal?
Adding silver to nitric acid makes a solution of silver nitrate.
Once the silver is in solution, the solution will contain Ag+ and
NO3- ions. If you add a piece of pure, clean solid copper, the copper
will “swap” places with the silver in a displacement reaction (the
copper is more reactive than the silver) and the pure silver will
precipitate out of solution as silver crystals which will cling to
the outer surface of the copper. The copper in the original alloy
will stay in solution.
At the exposed copper surface you will have copper nitrate and pure
silver metal crystals. The reaction is:
Cu(s) + 2AgNO3(aq) =E2=86’ 2Ag(s) + Cu(NO3)2(aq)
Then you should be able to gently shake the silver crystals off the
copper to bring more silver out of solution. If all the copper
dissolves you could try adding more copper to see if you can get
more
silver out of solution until all has been recovered. Then it’s a case
of filtering it and rinsing to get pure silver.
Have fun, it’s a reaction the kids at school used to love when I was
teaching as you can see the fine silver crystals growing before your
eyes.
Helen Hill
Preston, UK
No matter how you get the silver out of solution you have a large
quantity of nitric acid and metal salt solution to dispose of. The
cost of getting rid of this legally is much greater than the cost of
paying someone to refine it. Not to mention the safety hazards of
handling these chemicals in the volume you will need to do this. You
will be amazed at cost of the amount of acid required to put even 1
oz of silver into solution. This is just not a reasonable way to
spend your time or money. Given the costs of the time, chemicals,
equipment and disposal service required there is no way you can save
enough money to make DIY refining pay. It is fun to do it once to see
it work but…
James Binnion
@James_Binnion
James Binnion Metal Arts
360-756-6550
Adding silver to nitric acid makes a solution of silver nitrate. Once the silver is in solution, the solution will contain Ag+ and NO3- ions. If you add a piece of pure, clean solid copper, the copper will "swap" places with the silver
I haven’t actually done this, but it’s what I was taught as the
“standard” way to do this. Make a strong solution of NaCl (table
salt) and mix it with your (diluted) acid. It will form silver
chloride which, being insoluble in water will fall out of solution.
Filter and then heat the powder with some ventilation. The chlorine
will be driven off, leaving behind pure silver. Helen’s way will work
fine, too. The salt solution will get 100% of the silver, though.
This is from some etching literature I read somewhere along the way.
G’day;
I wrote something like this a long while ago but since the subject
has ‘rose again’, here we go: When Mr William Bunker Hunt tried to
get a corner on silver, the price of silver nitrate (essential in a
chemistry teaching lab then) went up to a couple of hundred dollars
or more for a bottle of 250 grams. So my wife, responsible for
servicing two 400 student labs put out large empty bottles to collect
all silver residues. She precipitated out all the silver as chloride,
filtered and washed it, then dissolved it in sodium cyanide. She
reclaimed pure silver by simply passing a small electric current
through the sodium silver cyanide, and the silver plated out on a
piece of stainless steel where it was easily stripped off the
stainless by hand. (The cyanide could be used again) After thorough
washing, the silver was redissolved in nitric acid, the silver
crystalized out, was washed and returned for use. She fitted this in
with all her other work. A long time ago.
Poor dear now has Alzheimers disease and can barely speak.
Cheers, johnb
The problem as I see it with going the NaCl route is that you now
have silver chloride, and the decomposition of that gives off
chlorine, a poisonous gas. Even with ventilation you might be safe (a
relative term), but what about the world out side your building?
Small amounts is toxic (might not be fatal), and even smaller
amounts have a huge impact on the environment.
Go the copper route, the product produced is pure metallic silver,
and copper nitrate can be used in the garden (if your plants are
short of copper) as a trace element supplement. As for disposing of
nitric acid, neutralize with sodium bicarbonate. You end up with
carbon dioxide and sodium nitrate (a fertilizer, and the oxidising
agent used in gun powder)…
Thomas.
Hi John,
I’d not come across your salt reaction before but it sounds a good
method. The addition of copper metal will also pull out 100% of the
silver al long as you use enough copper. If all the copper dissolves,
chances are there’s more silver in solution so you add another piece
of copper. Thick copper wire made into a coil (with some sticking out
of the top of the beaker so that you can agitate it) is good for a
larger surface area. Keep agitating it now and then to knock the
silver crystals off and re-expose the copper surface so that the
reaction can continue.
Looking at the two reactions, and consulting the MSDS sheets for the
disposal of the waste products, ie. copper nitrate in the case of
adding copper metal, or sodium nitrate in the case of adding salt,
the salt method does produce a less hazardous waste product and so
it is preferable.
Helen
UK
I haven't actually done this, but it's what I was taught as the "standard" way to do this. Make a strong solution of NaCl (table salt) and mix it with your (diluted) acid. It will form silver chloride which, being insoluble in water will fall out of solution. Filter and then heat the powder with some ventilation. The chlorine will be driven off, leaving behind pure silver.
I have done this. I simply added non-iodized table salt to the
diluted-with-distilled-water acid/silver solution.
But “some” ventilation is a gross understatement. You need A LOT of
ventilation. Same goes for the above term “heat” which seems to imply
a gentle warming (though it doesn’t really say that.)
It requires too much oxy/ace to be worth doing, and a huge torch,
preferably a 2ft.+ cutting torch.
Hi John,
I haven't actually done this, but it's what I was taught as the "standard" way to do this. Make a strong solution of NaCl (table salt) and mix it with your (diluted) acid. It will form silver chloride which, being insoluble in water will fall out of solution. Filter and then heat the powder with some ventilation. The chlorine will be driven off, leaving behind pure silver. Helen's way will work fine, too. The salt solution will get 100% of the silver, though. This is from some etching literature I read somewhere along the way.
Twenty years ago this is how I was taught to drop the silver out of
solution by someone we both know with the initials EF, he used to
have his studio in your building. The recovery of silver from the
acid was talked about in the workshop but never preformed for the
students as the focus of the workshop was on gold refining. The
problem comes in the heating to reclaim the fine silver from the
silver chloride, your “some ventilation” had better be damn good
because a small whiff of the pure chlorine gas coming off your
silver chloride will burn your throat and lungs badly and could kill
you. After attending this workshop I thought I knew what I was doing
so I went home and tried it on several ounces of silver recovered
from a film processing lab that I then dissolved in nitric acid. With
what I thought was adequate ventilation I reduced the silver chloride
to fine silver. I damn near put myself in the hospital, inhaling even
a small amount of chlorine gas is no fun. Never again
James Binnion
@James_Binnion
James Binnion Metal Arts
360-756-6550
It will form silver chloride which, being insoluble in water will fall out of solution. Filter and then heat the powder with some ventilation. The chlorine will be driven off, leaving behind pure silver.
G’day; Simply heating silver chloride will not ‘drive off chlorine*’
*Don’t believe me? Try it.
Cheers Johnb
I haven't actually done this, but it's what I was taught as the "standard" way to do this. Make a strong solution of NaCl (table salt) and mix it with your (diluted) acid. It will form silver chloride which, being insoluble in water will fall out of solution. Filter and then heat the powder with some ventilation. The chlorine will be driven off, leaving behind pure silver. Helen's way will work fine, too. The salt solution will get 100% of the silver, though. This is from some etching literature I read somewhere along the way.
John, as others have by now pointed out, this is a bad idea. I tried
it once. Filled a studio with acrid blue chlorine fumes. Not good. By
the way, to properly reduce it, you do more than just heat it (very
hot, by the way), it’s best to also add a reducing flux. I seem to
recall a mix of sodium carbonate and borax, but it’s been 25 years,
so that might be wrong.
However, there’s a better way. Go to I. Shor’s web site and poke
around a bit in the refining info. According to them, after dropping
out the silver with salt solution (or hydrochloric acid if you like),
you use ordinary Karo corn syrup with the still wet silver chloride
mass to reduce it back to silver.
The other classic way to reduce the silver chloride is also done
with the still wet freshly rinsed/washed mass, and that is to add,
with I think a trace of acid, zinc metal. Stirred around, it becomes
zinc chloride, which is soluable, while the silver chloride is
reduced to silver. That needs a bunch of zinc, though, and I suspect
that the corn syrup is cheaper and easier…
Peter
My preference would be the copper reaction. Although I didn’t realise
you could use the copper nitrate in the garden - thanks for that. The
copper reaction is simple and fun to do and as you say produces pure
silver.
Helen
UK