Today we've got the classic shake and bake reaction for you. The preparation of

potassium phiocyanate. Phiocyanate sounds scary but it's not. It's actually what cyanide is

metabolized to in your body and much less toxic. It's still slightly toxic though so use the normal

precautions. We're using our steel food shaker tin for this reaction. Okay here's our first

reactant. We've weighed out 15 grams of anhydrous potassium ferrocyanide. It's a

fine pale yellow colored powder as you can see. It's important that the salt is anhydrous and not

the dihydrate crystals. If you have these then dehydrate them in an oven at 150 degrees C for

a few hours and break up any lumps. Reactant number two. Here we've got 10 grams of finely

powdered sulfur. In theory the reaction requires five mole equivalents of sulfur for each ferrocyanide

so this is an excess. You'll see later that the excess sulfur burns off in the reaction.

And our final reactant. This is 4.3 grams of anhydrous sodium carbonate. Again it's important

to use the anhydrous salt which is a fine white powder. If you have the big translucent crystal

then you have the hydrate which you'll have to keep in order to remove all water. Here's our

three reactants.

Now we just need to transfer these to the steel pot and mix throughly.

Now we'll mix everything up. You can also shake if you really want the authentic experience.

Looking good. Okay firstly the safety note.

This reaction can generate cyanogen gas. This is extremely toxic, almost as poisonous as hydrogen

cyanide and will kill you very rapidly. Definitely use ventilation and perhaps consider doing this

outside. In reality the cyanogen tends to burn off but don't take any chances.

Okay we're going to heat the container now using a low heat. You don't need a lot of heat to begin with.

Pretty quickly you'll see smoke and the reactions starting to take place.

A few minutes into the heating the gas produced ignites. Even though we're only using a low heat,

There are also some blue flames which are due to the excess sulfur burning off.

After a few more minutes this part of the reaction is complete.

Now turn the heat up and get the temperature in the pot right up.

The contents become a semi-solid melt with a lot of very black colored fine powder suspended in it.

Keep heating very strongly for 15 minutes, then switch off the heat.

Before it cools, tip onto a heat-proof surface.

Then allow to cool.

The black solid is like rock and extremely difficult to crush up.

We've got just over 21 grams here from the reaction.

To extract we're going to use absolute ethanol.

We're not too sure how soluble the product is in hot ethanol so we're first going to

use 30 mils.

We get this warmed up in the microwave.

And first add this to our reaction pot in order to make sure we've got all product out.

Now into a beaker.

And we add the black solid.

If you've got a big heavy mortar and pestle then see if you can't powder the solid before

you add the ethanol as it will save you a lot of time.

The product is ready.

It's also apparently hydroscopic.

So we're covering up our beaker just to make sure that we don't absorb too much moisture.

Getting the mixture to stir was a bit of a pain in the ass.

We use a clamp to hold the beaker down safely.

Even with heating it's clear this isn't enough ethanol, so we added more to make up

to about 100 mils volume.

We left this heating hand stirring for 20 minutes.

It has finally weakened, and got the kind of liquid we need to get it up now in corn or

At the end of this time the lot of the solid had dissolved and we can see a fine white

powder forming where the ethanol evaporates on the side of the beaker.

While the mixture is still boiling hot, we filter.

Bring it up to a boil.

Here's the filtrate.

We covered this with plastic wrap to keep moisture out, and then placed it in the freezer

for an hour to see if we could get the product to crystallize out.

Here we go.

Lots of tiny needle-like crystals forming in the liquid.

At this point we did another extraction of the remaining solids using another 50 ml of

hot ethanol, and stirring and heating for another 30 minutes.

Most of the solids dissolved leaving the fine black powder.

So we filtered again.

And here we go.

This time, interestingly, we got crystals forming as soon as the ethanol solution entered

the cool filtration flask.

We combined the two sets of filtrates, covered the beaker, and then placed in the freezer

for a couple of hours to crystallize.

Here's the result.

A mass of crystals in the liquid.

We filtered these off.

And then got them as dry as we could in a few minutes on the pump.

Here's our first batch of pure product.

8.7 grams of potassium hyalcyonate of slightly damp cream-colored crystals.

This is a 55% yield from our starting ferrocyanide.

We'll do some tests later on but first we wanted to see if we could extract any more

product from the alcoholic filtrate.

First, we tried taking the filtrate and chilling it down again to see if any more crystals

would form.

But they wouldn't.

So now we just have to wait for a couple of hours to see if we can get the product

out.

Next we evaporated off most of the alcohol on a hot plate.

A white precipitate seemed to form and then disappeared again.

Once the mixture was down to a small volume we chilled it in the freezer again.

But no crystals formed.

It looks like water absorbs into this pretty easily.

So finally we put the residual solution into a petri dish and evaporated it down on a hot

plate.

A viscous liquid remained which then crystallized rapidly when cooled.

Here's our second batch.

4.1 grams of white solid.

It's probably more impure than the crystals, but it did give exactly the same results on

the chemical tests as the first batch.

It contains no cyanide, cyanate, or carbonate residue.

Okay let's do some tests.

Firstly, how hydroscopic is this stuff?

We placed a few crystals on a glass dish and left them in the air for a little while.

Humidity today is 60% so it absorbed water pretty fast if it wants to.

And 15 minutes later we've got a small puddle of water appearing.

So it's definitely hydroscopic.

Not enormously so.

You want to be careful with crystals that have a large surface area though.

Here's a small amount of iron chloride.

And we'll dissolve this in some water.

Dissolves pretty rapidly.

Now here's a little bit of water in a beaker.

And a small amount of our product.

Dissolves almost instantly.

Let's add to the iron.

And here's the solution.

An intense red color forms.

This is the classic test for thiocyanates, due to the formation of an iron-thiocyanate

complex.

It's a beautiful red-orange color.

If we pour this into a beaker of water and dilute it, it seems to change its red color

and become more orange.

Okay final test.

Here's some of our product.

A small beaker.

Now we'll add some 50% sulfuric acid.

There's a pink color formed initially.

But there appears to be no effervescence or gas formation.

But there is a strong acrid smell, a little bit like hydrogen chloride gas.

I-o-cyanic acid is unstable and can't be isolated.

So we're not too sure what this is.

Ehhh.

On breaking up the mixture, the pink color disappears and crystals of what look like an alkali sulfate form.

Here's our products again.

That was a nice little reaction and we've got an interesting product that we can do all sorts of things with.

Stay tuned to see what we've got planned.

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