Grow Silver Metal Crystals by Electrochemistry

Uploaded by NurdRage on 19.12.2010

Greetings fellow nerds. In this video, we're going to grow tiny crystals
of silver metal under the microscope. We're going to grow the crystals by electrochemistry.
The setup is actually very simple. I've tapped down an aluminum wire cathode
and a silver wire anode to this plastic tray. It's connected to these batteries through
a 470 ohm resistor to limit the current. Now the electrolyte is a saturated solution
of silver nitrate that i'm applying between the electrodes.
I don't need very much since we're going to be doing this under the microscope.
Now to slow down evaporation i'm putting this glass slide over the drop.
This also has the advantage of making the surface shape flat and allowing us to
easily keep focus under the microscope. Okay, let me take it to the microscope.
The deposition occurs on the cathode or negative terminal so that's where we'll focus our attention.
I haven't connected the battery and resistor yet so that gives me time to do so.
Now, first we'll look at highest magnification at the tip.
Let me connect the power through the resistor... and look at that!
Those are microscopic crystals of silver metal growing at the tip of the aluminum wire.
I'm actually time-lapsing this as the growth is actually very slow and is occurring over
the course of three hours. As it progresses you'll notice the crystals
getting all deformed and no longer looking like perfect crystals.
Two things are causing this, first the crystals are hitting the glass cover.
Second, growing crystals electrically is not an even process since the parts with highest
charge density grow fastest. Since charge density is not uniform for an
irregularly shaped object, crystal deformation is really hard to avoid.
Nonetheless, the time-lapsed results are still spectacular.
Let's try that again. This one i filmed over the course of ten hours
and under time-lapse you'll see a lot of things happening around it as it grows.
This is actually me fighting off various side effects like bubbles forming and the solution
crusting over every hour, forcing me to keep removing and cleaning the
slide. Every time i did so i disturbed the crystal
growth and thus it became even more deformed. Nonetheless, We're still seeing actual pure
silver metal electrically crystallizing out of solution.
Not a salt or metal ion, actual raw metal. This is not something most of us will ever
see in our lifetime. So what's happening is that at the anode,
which is not on screen, the silver metal is dissolving and releasing
silver ions into solution. At the cathode the silver ions are electrodepositing
on to the aluminum wire form silver metal. It's a very simple reaction, but its quite
amazing when you have a microscope to see it.
I'm using an aluminum metal wire as the cathode simply because I didn't have another silver
metal wire available. Here i tried it again using a diluted silver
nitrate solution. Since its not saturated it doesn't crust over
as quickly or produces as many bubbles, letting me film longer without disturbing
the growth. But as you can see, instead of hard crystal
edges, the dilute silver nitrate grows a more feathery
appearance of many smaller crystals. Kinda looks like I'm growing a silver tree.
A microscopic one. Now so far I've been limiting the current
with a resistor to get slow and controlled growth.
Now i'm going to apply the voltage directly to the electrodes.
Ready, go. That is not time-lapsed, that growth is actually
happening in real time with the much higher current.
The solution doesn't have time to diffuse in and form large crystals
so instead the crystals grow outward in branches composed of many smaller crystals.
OK I've stopped the current. These branches are actually quite fragile and will easily
fall apart. Now I'm putting the resistor in and going
with slow growth while time-lapsing the video. You can see the branches get thicker as now
the solution has time to diffuse in and deposit the silver more evenly.
But you'll notice the tips are growing faster than the stems.
This is because the charge density is greater at the tips.
Let's try that again. This time I'm going to use that large silver
crystal hunk we grew slowly a few runs back. Let me prepare the slide and get everything
into position. I'm also using saturated silver nitrate solution
for this particular run. I'm going to apply the current... now.
Whoa, that was different. Look at that,
we got a few things happening here. OK I've turned off the current, let's examine
our handy work. Look at that, these branches are composed
of different sized crystals, but mostly cleanly formed.
Back here at the base the original crystal hunk is now coated in a fine layer of small
crystals, kinda like frosting. Looking around here... oh look at that, looks
like some kind of silver metal plant. I betcha some sci-fi filmmakers are getting
ideas for an alien world from this. Anyway, I hope ya liked this simple experiment
into the microscopic beauty of electrochemistry. Thank you very much for watching. Please subscribe,
like and comment.