How to extract Silver from a Coin (or other silver containing material)

In this video we will extract silver
from a coin or another silver source. This method can be used to obtain nearly
pure silver when the silver is mixed in with other
metals. So you’re only going to need about less
than 20 milliliters of concentrated nitric acid and some silver coins or
another silver source. Please note that this experiment is more
fun than anything else and there will be a loss of silver in the process. It should also be noted that often the
amount of silver that can be extracted from the coin is less valuable than the
coin itself. First I added about 20 milliliters of
water followed by about twenty milliliters of concentrated nitric acid
and then swirl the solution around a little to mix it. Next I added a silver quarter to the
nitric acid. The nitric acid used here is in severe excess. I use the amount I did
for visual effect but it should be good for at least two quarters or multiple
coins. Also the purpose of diluting the acid is that the reaction with the
quarter is not violent. The reaction that is occurring is shown above. Silver reacts differently in hot
concentrated nitric acid than it does in cold or dilute nitric acid. So as you can
see in the equation above nitric oxide is produced. Nitric oxide alone is extremely toxic
and in the presence of air it produces nitrogen dioxide which you can see as
the brown fumes. For this reason it’s extremely important
that you carry out this reaction in a fume hood or a well-ventilated area. The color change is not due to the
reaction of silver with the nitric acid it’s actually due to the reaction of
copper with the nitric acid. After a while the solution will adopt a
more blue color. Once the coin is completely dissolved
and stopped bubbling add an equal volume of water. The solution is then filtered through
cotton to remove undissolved impurities. Small amount of water was then used to
wash of the container and to wash out the rest of the silver nitrate in the
funnel. Copper wire was then added to the
solution and it starts reacting. The reaction that is taking place is shown
above. The copper reacts with the silver nitrate in solution to displace the
nitrate ion and release silver metal. Another reaction that is
occurring is the reaction between copper and excess nitric acid. For this reason
it’s important to add an excess of copper in order to precipitate as much
of the silver as possible. Every so often you can poke the copper
pieces to dislodge the silver that has precipitated. You should also occasionally stir the solution. It is going to take quite a while to
react so I suggest leaving it here for a while and coming back. However eventually the reaction will be
done and you’ll know this one the bubbling has stopped and the solution is
cleared. The next step is to filter off the
silver. Pour through the filter paper let it drain and wash the empty beaker and
the silver precipitate several times using water. I used to squeeze bottle to knock down
the silver precipitate that was lodged on the side of the filter paper. The filter paper after draining was then
removed placed in a crystallizing dish and dried in an oven. This is what the silver looks like when
it is dried it looks like a nondescript gray powder which is quite different
from the metallic silver that you normally see. Now to reconstitute the
silver into the nice shiny metal that we normally see we need to melt it down. So
the first step is to add it to a crucible. Then using a torch the silver medal was
liquefied. It takes a little while for the silver to get up to its melting
point, so you’ll have to be a little bit
patient. I turned this crucible around as I was
melting it to form the silver into a large glob. I then poured the red-hot glob on to a
piece of wood for it to cool down. If you leave it in the crucible and let
it cool down it will stick to the crucible and be nearly impossible to
remove unless you shatter the crucible. This is what the final extracted silver
looks like. Note that this silver extraction is not
quantitative and silver will be lost in the process. I lost about ten percent of the silver
during the extraction process which is pretty bad. However this is most likely due to the
fact that I use much more nitric acid that I needed and I didn’t let the
copper sit in the solution long enough to precipitate all of the silver.

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