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Topic: Dehydrating alcohol  (Read 8753 times)

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Offline science2000

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Dehydrating alcohol
« on: February 08, 2006, 11:39:48 PM »
When one adds salt to a solution of, let's say, 70% isopropyl alcohol, the salt dissolves in the water and it seperates from the alcohol. The alcohol layer is on top. Is this alcohol 100% isopropyl, or is there still water in it that will not leave?
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Offline Mitch

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Re:Dehydrating alcohol
« Reply #1 on: February 09, 2006, 02:44:52 AM »
Quote from: science2000 on February 08, 2006, 11:39:48 PM
or is there still water in it that will not leave?

of course
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Offline science2000

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Re:Dehydrating alcohol
« Reply #2 on: February 09, 2006, 04:38:18 PM »
Really? Then anhydrous calcium chloride should take care of that, right? I mean, I can't see how water would be so attached to alcohol if something is "pulling" at it to drop out.
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Offline constant thinker

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Re:Dehydrating alcohol
« Reply #3 on: February 09, 2006, 08:18:32 PM »
If what your trying to obtain is pure ispopyl alcohol (or close to it), have you ever thought of using distillation. According to wikipedia isopropyl alcohol boils at 82°C. The isopropyl alcohol would boil off leaving the water behind. That would be dehydrating it as long as you collect the vapor.
« Last Edit: February 09, 2006, 08:20:31 PM by constant thinker »
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Offline mike

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Re:Dehydrating alcohol
« Reply #4 on: February 09, 2006, 08:37:18 PM »
Quote
According to wikipedia

constant thinker, did you look at the part about distillation? isopropanol forms an azeotrope with water so would be a bit difficult to simply distil it to dry it :)

I would suggest that you would need some sort of drying agent....
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Offline constant thinker

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Re:Dehydrating alcohol
« Reply #5 on: February 09, 2006, 08:40:15 PM »
I never knew that isopropanol formed an azeotrope at 60-70%. I just looked up the boiling point quickly for reference, that was all. Thanks for the info though.
« Last Edit: February 09, 2006, 08:45:05 PM by constant thinker »
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Offline Mitch

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Re:Dehydrating alcohol
« Reply #6 on: February 10, 2006, 12:18:45 AM »
Fractional Distillation and collecting over molecular sieves should get you >99% isopropyl alcohol.
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Offline billnotgatez

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Re:Dehydrating alcohol
« Reply #7 on: February 10, 2006, 06:55:41 PM »
Would anyone like to share their knowledge. At what point as the chain gets larger does the alcohol not form an azeotrope. Is it a 12 carbon alcohol?
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