Re: ORGLIST: Azeotropes

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From: Davor Kidjemet (Davor.Kidjemet$##$
Date: Wed Jan 10 2001 - 02:43:04 EST

> Does anyone know the definition of Azeotropes ?
> I am trying to remove acetonitrile and methanol from an aqueous solution
> through distillation. I can remove them completely due the formation of
> Azeotropes. Thanks for your information in advance!
> Wei Xing
> __________________

"Some mixtures of liquids, because of attractions or repulsions betwwen the
molecules, do not behave ideally; they do not follow Raoult's Law. There are
two types of vapor-liquid composition diagrams that results from this
nonideal behavior: minimum-boiling-point (eg. Methanol and chloroform) and
maximum-boiling-point (eg. HCl and water) diagrams. The minimum or maximum
poitns in these diagrams correspond to a constant-boiling mixture called an
azeotrope. An azeotrope is a mixture with a fixed composition that cannot be
altered by either simple or fractional distillation. An azeotrope behaves as
if it were pure compound, and it distills from the beginning to the end of
its distillation at a constant temperature, giving a distillate of constant
(azeotropic) composition. The vapor in equilibrium with an azeotropic liquid
has the same composition as the azeotrope."
From the book: D. L. Pavia, et al, Introduction to Organic Laboratory
Techniques" Saunders College Publishing, page 655


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