Water and ethanol form what is known as an azeotrope.
This occurs when a mixture of liquids has a higher or lower boiling point,
than each of the individual components. In the case of ethanol a mixture of ninety-five
percent ethanol to water boils at a lower temperature than pure ethanol.
So the concentration of ninety-five percent there's really nothing you can
do by distillation that can concentrate the ethanol further.
And luckily there are two other major methods that can be used to get to a
hundred percent.
Another method is to add another solvent to the mixture which forms an azeotrope
with water that's at a lower temperature than the ethanol-water one.
This way the other solvent and the water can be boiled off azeotropically and it
will leave behind pure ethanol.
The second method is the method I'm going to show and it's the one that's
easiest to do at home.
It's pretty simple and what will just be doing is adding a drying agent to the
ethanol that soaks up the water.
In a future video I'll show the distillation and how to get ninety five
percent ethanol from any percentage lower, but for this video I'm going to
start at ninety-five percent.
Luckily for me my local pharmacies simply just sells ninety-five percent
ethanol so it's a pretty simple starting point for me.
So now the question of why anyone would even want a hundred percent ethanol.
I personally need it because there's some reactions that I would like to run
where I need to use ethanol but I can't have any water present. Another major use
that I won't need it for but others may is to added to gasoline.
Anyway now to get started with the preparation.
First thing I'll do is use my hydrometer to verify that the ethanol is actually
at ninety-five percent.
So first it's placed into a grad cylinder and then they pour methanol in
until it floats.
Hydrometer functions based on the principle of buoyancy.
Water is more dense than ethanol so the more water that's present the higher the
density of the mixture and the more the hydrometer will be pushed out of the liquid.
All of this is to say that the concentration of ethanol is directly
related to its density and this tool lets us find it out pretty easily.
So we can see here that it's actually floating a bit above ninety five percent
which makes sense because the azeotrope is actually 95.6 percent.
I should also note that my hydrometer is specifically an alcohol hydrometer
so instead of density it reports alcohol concentration but you can also just use
a regular hydrometer which shows densities and correlated to a table online.
Just as a quick aside you can see when it's placed into just water that it's
pushed much higher.
So now that we see the ethanol is above ninety five percent we see we can drive
without using too much drying agent.
Its first added to a large container.
I have a stir bar at the bottom but it's kind of pointless because once enough
drying agent is added there really won't be much stirring happening.
And once all the ethanol is added we can start adding are drying agent.
From my drying agent I use what's known as molecular sieves.
These little sieves have very small pores in them which can absorb water but the
pores are too small to allow any other larger molecules to enter.
So this means that the small water molecules can find their way in and bind
to these little beads, but the ethanol is too big to do this and will be left untouched.
I should note that I used 3A molecular sieves because there are
different sieves sizes that will absorb ethanol.
I like to use molecular sieves because they're pretty easy to regenerate
afterwards by simply letting the ethanol evaporate and then driving off the water
using an oven.
However there are other drying agents that can be used. Some people use other
drying agents like magnesium sulfate or copper sulfate, but I really much prefer
the molecular sieves. Once the sieves are added the container should be sealed and
allowed to sit overnight.
I let it sit for several hours and then tested the concentration and
unfortunately wasn't really that close to a hundred.
The process of picking up water can be a little bit slow though especially no
stirring is happening.
Also my sieves were not freshly dried, so they might not be working optimally.
However because they can be pretty easily regenerated I opted to do the
overkill route. So I added about a hundred and twenty grams more.
Because the molecular sieves can be regenerated there really isn't a
downside in terms of molecular sieve loss by adding more.
However when the ethanol is decanted later a lot is going to stick to the
seeds and the more that you use the more loss will occur.
The solution is cloudy because of little bits of dust of the molecular sieves but
this really isn't an issue for now.
When allowed to sit overnight you can see all the dust settled to the bottom
and were left with a crystal clear solution.
So now we pour it in and we can see that it's pretty much a hundred percent.
So the next step is to separate the ethanol from the sieves and to do this
we're just going to use a coffee filter.
All of the wet sieves are dumped into the coffee filter to hope that some of the
ethanol drip through.
You'll notice that a lot of the dust from the sieves actually makes it through.
And the amount of dust that you get with your sieves will depend on the source
that you buy it from.
I bought mine for pretty cheap source and I think it had more dust than usual.
Anyway at this point you have to real options.
You can let all the dust settle to the bottom and decanted filter again and you
should be left with a pretty clear solution or you can distill.
Depending on your ethanol source you might want to distill it.
For example, mine was bought from the store and it has a lot of denaturing
agents that can actually be easily removed by distillation.
So for this reason I opted to distill. Note that the final solution of
anhydrous ethanol should be stored over sieves,
so if you're only reason to distill is to get rid of the dust it might not be
worth your time.
I then set up a fractional distillation but it is probably totally unnecessary
and a simple one will more than suffice.
In my case none of the denaturing agents are volatile so they should all be left
behind in the flask.
So this is what the upper part of the distillation looked like prior to
wrapping it with aluminum foil.
The column is in wrapped with aluminum foil to insulate it and help the ethanol pass over.
You can see that the receiving flask is packed with sieves to keep the ethanol
that comes over dry.
Eventually all the ethanol comes over and should be pretty much a hundred percent.
At the bottom of the distillation flask were left with a mixture of the
denaturing agents and the molecular sieve powder.
So to test out the ethanol concentration we again pull out our trusty hydrometer.
So we can see here that the hydrometer float is very nicely at the one hundred
percent mark.
So now we have some nice one hundred percent ethanol and we transferred to an
appropriate container.
In theory I could have just used the same bottle of the ethanol came in and
change the labels and I'm honestly not sure why I didn't.
Anyway once the ethanol is added then I dumped in a bunch of sieves just to keep it dry.
It's then capped, sealed off and labeled and were left with our nice hundred percent ethanol.
One thing to note is that the sieves dust really shouldn't be a problem as long as
you don't shake the bottle a lot before you use it. If you remain gentle when you
pour it all of the dust should remain near the bottom.
Anyway that's it for now and remember to store the ethanol somewhere safe.