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.