We wanted to do this reaction out of curiosity for a long time, so here goes.

We're going to prepare potassium permanganate starting with manganese dioxide.

Here we've got 20 grams of slightly damp manganese dioxide.

It's black in color and it's not the active type, but it's quite pure.

Next, our oxidizing agent.

We're going to use potassium nitrate given that this is relatively commonly available.

We're using the 1.5 molar ratio compound.

Prepare the manganese dioxide, which is 35 grams shown here.

And now our third ingredient, solid potassium hydroxide.

We're using this in the 2 times molar ratio, and this is 26 grams.

So here's our three starting materials.

The manganese dioxide and potassium hydroxide are in stoichiometric quantities,

and the nitrate is in the 50% excess.

To try to find the right amount of nitrate,

we're going to use a blender to encourage the oxidation reaction.

We put these together into a grinder to break them up into a fine powder.

But the potassium hydroxide is pretty good at drawing the water out of the slightly damp manganese dioxide,

so we ended up with a paste like this.

This might actually work in our favor by helping the starting materials to mix more intimately.

And even though the manganese dioxide looked fairly good,

it must have contained a fair bit of water because the temperature of the paste became quite warm.

So here's our favorite stainless steel food shaker container.

It's a bit rusty, but it will work fine.

So now we're going to put the paste into the container and pack it down.

Here we go.

And now we're ready to fire it up.

So we placed the container on our gas burner and applied full heat.

To begin with, a small amount of water bubbled and evaporated off.

This finished after a few minutes and we continued strong heating.

The material in the container turned soft and then began to form a melt.

You can start to see a green color appearing in the mixture.

We heated for about 30 minutes until there was quite a lot of liquid in the container bubbling away.

At this point, the green color had become so dark and intense that it was almost black.

We emptied the container.

Allow it to cool.

As it solidifies, you can see the green color again more clearly.

Once cooled down, we first washed out the container using 50 ml of boiling water.

And then we transferred this to a beaker containing the cooled solid.

We then placed this on a hot plate and heated to boiling point to help dissolve the lumps.

Using a magnetic stir bar to agitate the mixture, this took about 30 minutes.

To convert our solution of potassium manganate to permanganate, there are a few options.

But we're going to use the most OTC one, which is using sodium bicarbonate.

We're going to add this to the hot mixture.

This will cause the manganate to disproportionate into potassium permanganate and manganese dioxide,

the same black precipitate that we started with.

We've added about 30 grams of sodium bicarbonate now.

And as you can see, the mixture has become much darker and more viscous due to the precipitate forming.

But you can also see the purple color of permanganate.

Let's take a look at the top of the mixture and place it into some water. You can see it better.

Although there's a lot of brown manganese dioxide here too.

We added another 50 ml of hot water to the mixture to reduce its viscosity, then set up for filtration to remove the manganese dioxide.

The solution was still hot, so actually now allow any salts to crystallize out.

You can see the intense purple, almost black color in the filtrate.

Filtration took a little while and made rather a mess, as you can see.

Make sure you've got some sodium bisulfite solution handy when you do this reaction.

We washed the brown manganese dioxide precipitate with about 20 ml of boiling water.

Then got off as much filtrate as we could.

Here's the filtrate we obtained.

A still hot and quite viscous solution which contains not only potassium permanganate but also a lot of sodium and potassium salts.

We wanted to do an experiment with this and see if it was possible to get solid potassium permanganate crystals.

After all, potassium permanganate is highly soluble in hot water but much less soluble in cold water.

So we first chilled the solution down to about 15 degrees C.

As you can see something has crystallized in the mixture.

So we filtered again to see what we've got.

Again, a very dark intense filtrate.

And a mass of what came to be needle-like crystals.

We washed these with a little ice cold water.

And then got them dry on the pump.

Here's a portion.

And as you can see they've lost color with washing.

This is definitely not potassium permanganate.

But the good news is that our filtrate now contains less impurities.

So we chilled down further to 70 degrees C.

In order to see what else would precipitate out.

Some more crystals.

So we filtered again.

And again washed the solid with some ice water before drying on the pump.

And here we go.

But as you can see the crystals are fluffy.

And again this is not potassium permanganate.

To cut a long story short we tried a few more times.

But we couldn't get any solid crystals just by chilling down the filtrate that we had.

You would need to actually evaporate off the water and keep crystallizing.

Let's test the oxidizing power of our filtrate solution though.

We've got about 5 mL in a small beaker here.

We've got the thermometer rigged up to record the temperature.

Here's about 1 mL of ethanol.

You can see a color change to blue.

Then to green.

Then to brown.

You can see the yellowish brown colored manganese dioxide precipitating.

As the permanganate oxidizes the ethanol to acetaldehyde.

And a 10 degree temperature increase.

We're quite pleased with this.

We were expecting to get a vaguely pink solution.

Not the very intense and fairly concentrated solution that we actually obtained.

To get solid crystals though is difficult unless you are prepared to evaporate the filtrate down and keep crystallizing until one of the fractions ends up being the permanganate.

The color of the solution is elusive.

Even very dilute solutions have an intense color.

Thanks for watching and stay tuned for some more interesting manganese chemistry.