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Topic: What is Azeotropic Drying  (Read 12280 times)

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Offline Vermilion

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What is Azeotropic Drying
« on: September 22, 2013, 08:22:26 PM »
I understand what an Azeotrope is and I understand that some zeotropes can be turned into an azeotrope to properly distill or separate the compounds ( or so Wikipedia says ) but i still cannot figure out what Azeotropic drying is?

Offline spirochete

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Re: What is Azeotropic Drying
« Reply #1 on: September 22, 2013, 08:29:19 PM »
Water has a relatively high boiling point compared to many other liquids. Many organic liquids form azeotropes with water that have a lower boiling point than water itself. An application of this is in drying glassware. After cleaning with water and whatever else you need you finish up with acetone rinse. Acetone forms an azeotrope with water and your glassware dries quicker than it would otherwise.

Offline Vermilion

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Re: What is Azeotropic Drying
« Reply #2 on: September 22, 2013, 08:32:57 PM »
Oh wow that makes so much sense, thanks!

Offline DrCMS

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Re: What is Azeotropic Drying
« Reply #3 on: September 23, 2013, 04:17:31 AM »
Acetone forms an azeotrope with water.

NO it does not.

Offline AlphaScent

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Re: What is Azeotropic Drying
« Reply #4 on: September 23, 2013, 10:14:41 AM »
Definitely no azeotrope formation between acetone and water.  When you are drying in a laboratory setting it is most likely drying material using toluene and a Dean-Stark trap.  I am today drying aluminum isopropoxide using this method.
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Offline spirochete

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Re: What is Azeotropic Drying
« Reply #5 on: September 23, 2013, 10:59:22 AM »
Acetone forms an azeotrope with water.

NO it does not.

Wow sorry you're correct.  I distinctly remember a fifth year PhD student told me this once when I was a first year in grad school. Its drying utility must be that it simply washes away the water, followed by easier evaporation of the lower boiling acetone.

Offline Archer

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Re: What is Azeotropic Drying
« Reply #6 on: September 23, 2013, 12:49:16 PM »
I understand what an Azeotrope is and I understand that some zeotropes can be turned into an azeotrope to properly distill or separate the compounds ( or so Wikipedia says ) but i still cannot figure out what Azeotropic drying is?

My understanding of azeotropic drying, as I have used it, is simply boiling a material in a solvent which forms an azeotrope with water and collecting the water as it condenses and separates from the azeotrope.

For example, if you wanted to dry an air sensitive compound which is an oil at room temperature then you can set up a Dean-Stark apparatus under an inert atmosphere  with a solvent such as toluene to drive off the water(as described by AlphaScent). This is sometimes much faster than using a high vaccum line (or more appropriate if your substance is relatively volatile) and gives a sample which is sufficiently dry for many applications.

You can also use a solvent such as dichloromethane for heat labile substances where a Clavenger Apparatus is employed rather than a Dean-Stark.

In both of the above cases it is possible that the returning "wet" solvent causes an issue, in this case it is possible to dry the returning solvent by way of a soxhlet extractor filled with molecular seives rather than a Dean-Stark. This also works well for removing low MW alcohols such as methanol or ethanol.
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Offline curiouscat

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Re: What is Azeotropic Drying
« Reply #7 on: September 23, 2013, 01:04:05 PM »

My understanding of azeotropic drying, as I have used it, is simply boiling a material in a solvent which forms an azeotrope with water and collecting the water as it condenses and separates from the azeotrope.


Needs a heteroazeotrope though, right? I'm being pedantic, sorry.

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