This is an excerpt of an article that I ran across the other day. I am often asked what is the highest proof that you can get, ell here is your answer.
The
highest proof alcohol you can buy is Everclear, at 190 proof. That's nothing!
Let's get together and make an alcohol that's 200 proof! Except we can't
possibly do that. There's a physical limit to how pure alcohol can actually
get, and we'll tell you why. Ethanol,
the business molecule of alcohol, is more volatile than water. Given any set of
conditions, it will be more likely to fly away than water molecules. This includes
higher temperatures. Heat up a mix of ethanol and water, and more of the
ethanol will go away. This proved a bane to liquor makers, until someone
stumbled on the secret of distillation. Heat up a mixture of ethanol and water
to a point where the alcohol boils but the water (except for the stray molecule
or two) does not, and you can make a liquid that's pure water and collect a
steam that's pure ethanol.
Few
people actually wanted pure ethanol, though. Though a little extra kick was
good, only the hardcore drinkers demanded pure alcohol - and they weren't going
to be repeat customers. So it took a relatively long time for people to realize
that no one could make pure alcohol or pure water from ethanol and water.
This
is because ethanol is not an ordinary mixture, it's an azeotrope. Instead of
boiling purely and separately at two different temperatures, its vapor will
form a certain proportion. Steam from alcohol is 95.57 percent alcohol. Get a
pot of 95.57 percent ethanol boiling and the steam will be 95.57 percent
ethanol right down until the last drop evaporates. That's the limit.
