we're going to be looking at alcohol
today and in particular ethanol because
ethanol is the alcohol that most of us
are most interested in its Martin how
was the filming Martin it's only just
begun
this is a model of ethanol two carbons
five hydrogen's here oxygen here and
another hydrogen there most people are
familiar with alcohol because of
alcoholic drinks
one of my colleagues at my old
university did point out it looked a bit
like a dog shape so although hair of the
dog is an English term referring to an
alcoholic drink you drink in order to
combat hangover it doesn't come from the
shape of the molecule beer wine all
sorts of things like vodka these are all
made by fermentation of some natural
material maybe juice from some sort of
fruit like a grape or some sort of grain
wheat barley and so on today what we're
going to do with all these different
alcoholic drinks is actually disturbance
of distillation will actually purify
these alcoholic drinks it will mean that
we can actually get as close to pure
alcohol as we can alcohol has been
terribly important in human history
because in the days before people
discovered how to purify water they used
to drink weak beer where the alcohol
killed most of the bacteria and so they
could drink safely in Asia people used
to boil water and make tea but this
wasn't discovered in Europe and and the
West till many many years later right
what we're going to do now is actually
distill the alcohol out of a kind of
beer
so the beers going to go into that large
flask there we'll connect it up to this
which is known as the steel head on top
of that will be a thermometer alcohol
vapor will collect around here go down
this arm and into this bit now here
we've actually got some cold running
water creating a jacket of coolness
around the glass tube inside it so the
alcohol vapor will get condensed into a
liquid that will flow down into the
receiver into our round bottom flask
alcohol has now suddenly or ethanol
ethyl alcohol has become enormous Lee
important as a possible means of solving
our transport problems you can burn
- no in car engines you can mix it with
gasoline to produce a material which
will still operate in car engines you
can make the ethanol from all sorts of
different grains from wheat from maize
guitar dope or pints for a living that's
ridiculous
I truly a visible job ok there we go can
a beer in the flask and now we're going
to heat that up the ISO mantle is now
heating up so that were actually heat up
the sides and the bottom of this round
bottom flask so what's going to happen
is that you've got alcohol and water
inside that vessel the water should stay
in there until you know if we go up to
100 degrees C only then will it boil but
before we get to 100 the alcohol will
come off first around about 78 degrees C
any organic compound that contains an
oxygen hydrogen group is known as an
alcohol people when they talk about
ethanol usually also call it alcohol but
you can get so called methyl alcohol
methanol which has ch3oh and you can
make this methanol by distilling wood
and it's sometimes known as wood alcohol
it's very imposing 'us causes blindness
and quite frequently that methanol is
added to ethanol to stop people drinking
it so called methylated spirits but
there are whole series of alcohols
propanol butanol Penton all and so on
and all of them are used in making
chemicals doing chemical reactions but
ethanol is by far the most common and so
alcohol when chemists are talking is
often a shorthand for ethanol but the
alcohol there which is bubbling up
forming alcohol vapor into this area
here which is the steelhead
so what will happen is it's coming
across there as vapor but once it hits
this cold part of glass
it condenses on it it's trickling down
flows along the condenser so what we're
getting right at the end here into the
receiver and then into the round bottom
flask is the alcohol from beer one of
the problems when you distill alcohol
from water is that you cannot get it a
hundred percent pure because ethanol and
water form a so-called azeotrope what
distills over is 97 or 98 percent pure
but you can't get rid of the last two
percent of water the only way you can
remove it is by adding a third material
quite often people add benzene to it so
the alcohol that we have in the lab
doesn't contain much water but it does
contain nasty things which means that if
you drink them you can be seriously
poisoned for this kind of beer we've
managed to get about this much alcohol
so not a huge amount but that's what
we've managed to achieve on our crude
distillation apparatus here but there
you go I drink some wine but
unfortunately I don't like beer which is
a real disadvantage in some countries
where beer drinking is a big tradition
so I'm fail in when I go to countries
like Germany or Belgium
I can't really appreciate their national
drinks we're going to be putting some
fortified wine now into our round bottom
flask and then that will be connected to
the distillation apparatus alcohol is
used in the lab quite frequently very
often as a solvent for doing chemical
reactions it can also be used just for
washing things because it will dissolve
quite a wide range of organic compounds
so if you wash your flask in alcohol
then you can get nice clean glassware it
should come off about 78
there are bacteria that can oxidize
ethanol they turn ethanol into ethanoic
acid acetic acid it's what makes vinegar
and so if you have a bottle of wine it
and leave it open to the air or air
leaks into the bottle it starts getting
acid it becomes more like vinegar and
when I was a teenager again
I was quite an enthusiastic chemist and
my father opened the bottle of wine
which was a bit acid so I had this
brilliant idea
I took a so-called ion exchange resin
that removes the acid from anything and
I poured his wine through the ion
exchange resin it was a fantastic
success it stopped being acid but it's
tasted absolutely foul right and there
we have it so there's a wine there's the
alcohol from it Cheers