Warning: Sodium hydroxide is corrosive.
Wear gloves when handling it.
Greetings fellow nerds.
In this video we're going to make zinc powder by electrochemistry.
Start with 400 mL of water and add to it 130 g of sodium hydroxide.
Stir it until it dissolves.
Now add zinc oxide until it stops dissolving.
I added about 40 g in two 20 g portions.
Zinc oxide can easily be bought from pottery supply companies and soap making suppliers.
What is happening is the zinc oxide is reacting with the sodium hydroxide to form sodium zincate.
Now I'm going to let the mixture stand overnight to settle and decant off the clear solution.
I tried filtering it but my zinc oxide was so fine that it passed right through.
Anyway, here we are with the decanted clear solution of sodium zincate.
Now we insert our electrodes.
For the positive terminal or anode I'm going to use nickel strips.
The great thing about this alkaline zincate process is that it's not as corrosive as acidic
processes
and thus can use cheaper and easier to obtain nickel electrodes
rather than expensive platinum or toxic lead dioxide electrodes.
For the negative terminal, or cathode,
I'm going to use this copper circuit board.
A zinc plate would be better but I didn't have one.
Once both electrodes are in raise the current until the cathode just starts to bubble
then dial back about twenty percent or so until it stops.
We want the zinc to come out and not the hydrogen.
So what's happening is that at the cathode the zincate ions are being reduced to zinc
metal as well as hydroxide.
At the anode, the hydroxide ions are oxidized into oxygen.
Overall we're converting the sodium zincate into sodium hydroxide, zinc metal and oxygen.
Now sodium hydroxide was what we originally used to dissolve the zinc oxide
so it's really just behaving as a carrier.
What we're essentially doing is splitting zinc oxide.
Now if you look at the zinc surface,
you'll notice it has a somewhat sandy texture to it.
The crystals of zinc metal produced in this process don't bond very strongly so rather
than a metal plate,
we're getting more of a metal sponge that will crumble when we recover it.
Anyway, i'm going to let this go overnight.
And here we are the next day.
Let me turn off the current and remove the nickel anodes so you can see what we've obtained.
So we have a nice thick deposit of zinc.
You'll notice that even though we've turned off the power
and remove the anode the zinc is still bubbling.
This is because we've depleted the the solution of zincate
and now we're left with a concentrated solution of sodium hydroxide.
Zinc actually reacts with concentrated sodium hydroxide to form sodium zincate again and
hydrogen gas.
Stopping that reaction is easy enough.
Remove it from the solution and give the zinc a good wash with water.
Now leave it to dry.
In the meantime, if you want to make more zinc,
just mix the solution of sodium hydroxide and leftover sodium zincate with more zinc
oxide and electrolyze again.
If you want to make lots of zinc,
you don't even have to decant the solution and you can just electrolyze it directly.
The sodium hydroxide produced will dissolve more zinc oxide
and thus keep producing zinc until it's depleted.
I just decanted it because i wanted a clear solution to show you the chemistry.
You don't need to do this.
Anyway, back to the zinc metal.
It's a couple of hours later and the zinc has taken tarnished appearance
because it's reacted with the air to produce a layer of zinc oxide.
This is only a surface discoloration and the zinc underneath is still fine.
Now, just scrape off the zinc.
As you can see, it's crumbling into a powder.
If you need powdered zinc for your chemical reactions, this is a great way to produce
it.
And there is our powdered zinc.
It's a bit damp but you get the point.
You can use this for reduction reactions.
You metal refiners might want this for displacing other metals from solution.
And you metal casters might use this as a source of zinc for zinc casting.
Now as i said before, this alkaline zincate process only produces zinc powder.
If you want a strong and solid zinc plate you'll need to use an acid sulfate process.
I'll be demonstrating that in my next video.
Thanks for watching.
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