In this video we're going to prepare Potassium Iodate starting with Potassium Chlorate.

There are a few different ways to do this, but the most photogenic use is solid iodine and that's the method we'll be using.

We're starting off here with 17.5 grams of Potassium Chlorate crystal.

Here's 50 mils of warm water.

First we'll place the water in a 250 mil conical flask.

And then we add the Potassium Chlorate to this.

We've set this up on a hot plate.

And now we're going to heat and swirl the flask until the solid has nearly dissolved.

The salt isn't net soluble so this will take a little while.

We've also added a thermometer so that we can see the temperature.

Getting up past 70 degrees C now.

And the Chlorate is nearly all in solution.

Here we go.

Our reaction also needs a catalyst.

To kick things off.

So we've got a small beaker here with some 68% concentrated Nitric Acid in.

We're going to add about half a mil of this to the hot Potassium Chlorate solution.

Okay everything is in solution and the temperature is around 80 degrees C.

So we're ready to go.

Have a bowl of water standing by.

The rest is up to you.

The reaction isn't that vigorous but just in case you may need this to help moderate it a bit.

So here's our final reactant.

20 grams of solid Iodine.

This reaction will apparently work with Potassium Iodide.

And you can even perform it in the molten state.

But we've not tried these so we can't say if it works as well.

So now we'll add the solid Iodine to our hot Chlorate mixture.

everything is in the flask now and we continue to heat gently purple iodine

vapor starts to appear in the flask and soon the iodine starts to jump around as

starts to take place.

The yellow color appears transiently where the iodine reacts.

We've covered the top of the flask with some plastic wrap to try to stop iodine vapor from

escaping.

You'll notice the temperature of the mixture steadily increasing as the reaction takes

hold, especially above 90 degrees C. At around 105 degrees the mixture will boil and we don't

want this.

So at around 100 degrees C place the flask into the water bowl just for a few seconds

in order to get the temperature back down to around 80 to 90 degrees.

Then place it back on the heat and allow the reaction to continue.

You'll see the iodine slowly being consumed.

If the temperature rises too high again, repeat the cooling process if you need to.

A complex reaction is taking place and the iodine is being oxidized by the chloride and

the nitric acid mostly to iodic acid.

A small amount of chlorine gas is also produced, but not much.

It's sensible to use ventilation though just in case.

It's a nice reaction to watch.

After about 15 minutes the iodine is nearly all consumed.

Here we go.

Now we'll need to boil the solution gently for a further 10 minutes or so in order to

get rid of any chlorine gas forms in the process which may be dissolved in the solution.

And now we're done with the main reaction.

Let's check the pH of the mixture.

Strongly acidic as you can see.

And also slightly bleaching, ensuring the indicator paper white.

Since most of our iodate product is now in the solution as iodic acid, we now need to

neutralize the acid.

To do this we'll make up a solution of potassium hydroxide in water.

You'll need about 7 or 8 grams in total.

Add slowly to the hot reaction mixture.

The heat of neutralization is going to cause a little boiling.

After a while you should see a fine white precipitate forming.

This is our product.

Potassium iodate.

Which isn't very soluble.

Potassium iodide is soluble in water, especially with a lot of potassium chloride as a reaction

product also present.

Keep going with the neutralization using potassium hydroxide solution.

Let's check the pH again.

Strongly alkaline.

It doesn't matter if you overshoot the mark slightly, but don't add too much alkali or

else your product will be impure.

And here we go.

Now we'll leave our reaction mixture to cool down until it reaches room temperature and

then we'll chill it for a bit in order to make sure that we've got as much potassium

iodate out of the solution as possible.

Here's the chilled mixture.

There's a fine white precipitate of potassium iodate.

So we filter this off.

Cool.

Perfect.

Cool.

Perfect.

And we wash a few times with a little cold water, then dry the solid thoroughly.

Here's our final product, 28 grams of very fine fluffy snow white micro crystals of potassium

iodate.

This is a 93% yield on the potassium chloride that we started with, which is not bad.

If you want an even purer product you can recrystallize this quite easily from boiling

hot water.

This is a very successful reaction so we wondered what would happen if we used potassium perchlorate

in place of chlorate.

Would we get potassium periodate?

Or would we simply get potassium iodate as a result of the oxidation?

Or would we get no reaction at all?

Okay place you bets now because we'll try this now on a smaller scale using 5 grams

of potassium perchlorate here.

We use 25 mils of water to dissolve the potassium perchlorate using a conical flask as before

and heated on a hot plate.

We added about one third of a ml of potassium perchlorate.

percent nitric acid. At about 90 degrees see the perchlorate salt mostly went

into solution. Here's the iodine. We're using a slight excess stoichedomevi as

before so this is just over 5 grams. So let's add the iodine and see what

happens. The iodine starts to bubble around but this could just be because

the mixture is already at boiling point.

We're not seeing any spontaneous temperature rise in the mixture though.

We add the rest of the iodine. With the temperature some of this vaporizes and

forms a lot of purple fumes. We take the mixture off the heat to see

if the bubbling is self-sustaining as an indication

that a reaction is taking place but on cooling slightly it does down.

On heating again the mixture boils but the iodine doesn't seem to be going into

solution even after some time. So this reaction doesn't work. Fundamentally

potassium chlorate is a good oxidizing agent for iodine in this reaction

because it is less stable than potassium perchlorate despite being a

theoretically weaker oxidizing agent.

So having proved that you need potassium chlorate to do this let's go

back and test the oxidizing power of our potassium iodate product using our

favorite test with red phosphorus of course. Let's give them a good mix.

Okay let's try using a very hot steel hole.

The mixture even smokes but there's no obvious reaction.

Let's try again.

Well that proves that potassium iodate is a strong oxidizing agent but just like potassium

perchlorate in our previous video it seems to be quite stable.

It's actually specified as having a longer shelf life than potassium iodide which is

easily oxidized.

Thanks for watching.