- [Instructor] Let's say that you have a solution
that where the solvent is water
and the solute is what
we would consider drinking alcohol or ethanol.
So this is our solution right over here.
And let's say that it is 10% ethanol,
which is drinking alcohol.
And let's say the rest of it is water.
And what we wanna do is
figure out a way that we can get something
that has 15% or 20 or 30% ethanol.
How would we do it?
Well, the answer lies in the fact that ethanol
and water have different boiling points.
For example, the boiling point of ethanol
is approximately 78 degrees Celsius.
While the boiling point of water
is 100 degrees Celsius.
And so a mixture of ethanol
and water is going to have
a boiling point someplace in between.
And so you could imagine
we can keep heating up this solution.
We're going to go beyond
the boiling point of ethanol.
But before we get to the boiling point of water,
this solution is going to boil.
And when it's boiling,
because ethanol has a lower boiling point,
the vapor mixture is going to contain
more than 10% ethanol.
And if you could condense that vapor,
you then have a solution
with higher than 10% ethanol.
And that is exactly what distillation is all about.
So you might distill with a contraption
that looks like this.
At first, it looks complicated,
but then when you really understand what's going on,
it's actually pretty straightforward.
It's exactly what I just described.
So what we would do is
we would put the original solution right over here,
and then you would heat it up.
Oftentimes you're gonna heat it up in an oil bath.
That's what you see
in this yellow right over here,
because the oil won't evaporate readily
and it can distribute the heat
around in a nice even way.
And then if you were to heat this up
so that the solution boils,
remember that's going to be a boiling point
someplace in between 78 degrees Celsius
and a 100 degrees Celsius.
You're going to for sure
have some water molecules vaporizing,
but at that temperature,
which is beyond ethanol's boiling point,
you're for sure we're going to have
a higher proportion of ethanol molecules vaporizing,
and then they're going to be,
they're going to be in vapor form.
And so they could enter this chamber right here.
And what this chamber is,
is essentially what's called a Condenser.
So oftentimes you're going to have
separate from the vapor,
but you're going to make water, cold water,
go around this tube right over here,
oftentimes a glass tube.
Sometimes you might chill it with cold air instead,
but you have water coming in, cold water,
and it's going around the tube.
It's not mixing with the actual air inside the tube.
And then the water comes out of the tube.
But what it does is it lowers
the temperature in that tube.
And so you can imagine the vapor
that comes in that contains
both ethanol and water,
but it's a proportion of the vapor
that is ethanol is going to be higher
than the proportion in our original solution.
It's going to condense back into liquid form.
And then that stuff is just going
to pour back down into
what you could call this collection chamber right here.
And the collection chamber
is surrounded by a very cold,
oftentimes ice bath so that you minimize vaporization.
Depending on how well you do this,
maybe this sample right over here
might be 20% ethanol
or 30% ethanol.
There will be still some water
that comes up here and condenses,
and then comes back down.
Now, if you wanted an even pure sample of ethanol,
you could keep doing this.
You could take what you collect here
and then heat that up
to its boiling point,
which will now be a little bit lower
than the first solution,
because it has a higher proportion of ethanol.
And then you would have
the same process go over
and over again.
And so every time you do that,
you would get a pure
and pure sample of ethanol.
If you don't wanna do that,
'cause it's tiring.
It takes a lot of work.
And actually you end up with
a lot of lost material
through all of this mechanism over here.
There's something you can do called Fractional Distillation.
And what fractional distillation is,
is getting multiple vaporization
and condensation cycles all at once
so that you get a more pure sample.
And the way that you get
those multiple vaporization in condensation cycles
is to give the vapor in this tube right over here,
something to condense on
and that condensates,
some of it will revaporize.
And some of it will drip back down.
And the part that revaporizes
is likely to have a higher proportion of the distillate
of the thing that has the lower boiling point.
And you can have multiple cycles of this condensation
and revaporization inside this column.
And so at the end,
you're more likely to have
a more pure sample of your distillate.