Today we're making some silver nitrate which is a salt of silver metal.
Silver nitrate has historically been used as an antiseptic and it has a few uses in chemistry.
I don't have any plans to use it in a synthesis reaction but I do want to
carry out some demonstrations. I want to finally get around to doing the silver
mirror experiment and I also want to mix it with some magnesium to make a water
sensitive explosive. I do already have a video where I demonstrate the mixture of
magnesium and silver nitrate, but I really want to revisit it.
In general the process to make silver nitrate is pretty simple.
The first thing we do is react silver medal with nitric acid to make a
solution of silver nitrate. The water is removed by evaporation and this leaves
behind our silver nitrate.
In terms of chemicals all we need for this preparation is silver metal and
some concentrated nitric acid. Both of the silver pieces that you see here weigh
about 31.25 grams which is a little bit above a troy ounce.
For the nitric acid I found a decent amount to use was a little bit more than a milliliter per
gram of silver. So to react the 60 2.5 grams of silver I used about sixty five
milliliters of the nitric acid.
To start things off I put the two pieces of silver into a beaker.
Onto the silver I then added about sixty five milliliters of concentrated nitric acid.
The silver loses its luster almost immediately after adding the nitric acid.
As we let the nitric acid sit with the silver it will take on a yellow color
but not much else will happen.
To get the reaction going we're going to have to heat things up a little bit
using a hot plate.
It's important not to heat things up too quickly because we don't the reaction to
be too violent.
What we really want to do is add enough heat for the reaction to get going on
its own and once it started it will generate its own heat and keep itself going.
As we continue to heat things the color will transition from a yellow to an
orange and eventually to a near red.
The overall reaction is shown here where silver is reacting with nitric acid to
form silver nitrate, nitrogen dioxide gas and water.
The nitrogen dioxide gas is what gives the solution its color and the more
nitrogen dioxide we produce, the darker the solution is going to get.
As the reaction starts to pick up we'll have a lot of bubbles coming off the
silver metal and will start to release some nitrogen dioxide fumes.
The fumes will get thicker and thicker and eventually the reaction will take off.
Once the reaction really got going I turned off the hot plate to prevent it
from getting out of control.
Nitrogen dioxide gas in general is dangerous to breathe so it's very
important to do this in a well-ventilated area.
As the silver continues to react will be building up some silver nitrate and it's
important to occasionally stir things. I'm not exactly sure why but initially
it seems like the silver nitrate has a hard time dissolving.
I think we might just be producing silver nitrate faster than it can
dissolve into the water but i'm not exactly sure.
When most of the silver is reacted the reaction will start to die down and
we'll start to dissolve some of the silver nitrate precipitate we see here.
The reaction now is much less vigorous but we're still just going to leave
things until most of the silver has dissolved.
As we get closer to the end the solution becomes more colorless and the color of
the nitrogen dioxide gas starts to fade.
The most annoying part is when we're very close to the end and we have just
some small pieces of silver left that seem to be taking forever to fully react.
Because most of the nitric acid has reacted its concentration of solution is
quite low and the reaction rate is pretty slow. In theory we could just
leave things and let it react but I was a little bit impatient so I added some
more nitric acid.
Not too long after adding the nitric acid all of the silver is reacted and
now we let things cool down.
As we let things cool down the solubility of silver nitrate in solution
will decrease and eventually silver nitrate crystals should come out.
Sometimes it happens though that we get a supersaturated solution and even when
it's cooled down no crystals come out.
To get the solution to crystallize I'm going to need to provide a seed crystal.
There were some crystals that formed on the watch glass so I knocked these in
and you can see immediately crystals start to form.
Once it looks like the crystallization is complete the solution is placed into
a freezer. When the beakers tilted on the side you can see all of the ice crystals
that are formed.
The first thing I did was dumped out any excess liquid.
I then place the beaker on the side let more liquid pool at the bottom and then
I dump that out as well.
When it seems like most of the water had been poured off I used the glass rod to
break up the crystals.
The crystals were then dumped out into a glass bowl.
After I dumped out all of the crystals I looked at the beaker and it seemed like
there was still quite a bit left over. To wash the beaker I use the water that we
had decanted out earlier.
Now we have a nice liquid mixture of silver nitrate in water and we have to
evaporate off the water.
My workspace is air-conditioned so the water came off quite quickly.
During this drying process it's pretty important to keep the silver nitrate in the dark
because it does degrade when exposed to light.
After just a few days I was left with some superdry silver nitrate crystals.
I crush the crystals into a powder using the bottom of a beaker and then I
transferred them to a container for storage.
As I said before the silver nitrate is sensitive to light
so I covered it with aluminum foil prevented from degrading.
The final yield of silver nitrate was 96 grams which corresponds to a percent yield of about
ninety-eight percent. These types of reactions where we just
reactive metal with an acid, usually have yields around a hundred so this isn't
too spectacular. Anyway now that I have 96 grams of silver nitrate this is much
more than I need.
Like I said before I want to use it to do the silver mirror experiment and to
make the water sensitive explosive with magnesium, but I'm not exactly sure what
I'm going to do this.
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especially those who donate five dollars or more. Anyone who donates and supports
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if you donate five dollars more, you get your name at the end of the video, like
you see here. In the next few months though I want to work on my Patreon page
lot and I want to get more rewards going and maybe even get some higher tier ones
and I want to also offer some Patreon exclusive content, also as usual here's
the videos that I've currently filmed and the ones that plan to work on, if you
have any suggestions or ideas, please feel free to leave them in the comments