Boiling Ethanol out of dH2O???

[kris_1108]

I understand that it is possible to 'boil' alcohol out of some NPs (taking advantage of the difference in Boiling Points.) Is there any reason why the same could not be done with a water/alcohol solution? Would the alcohol 'boil off?'

[embezzler]

repeat distillations if ethanol/h2o will yield more and more pure ethanol but afaik this reaches a limit of effectiveness in the mid ninteys where some other method of drying is needed....

havnt tried it but mgso4 should be able to dry the thing from here but i havnt tried this personally so maybe some other bee can finish..its probably in tfse

[alphacentauri]

There are some kind of solutions called azeotropes, which have a particularity: the boiling point of the solution is lower than the boiling point of the single components. These azeotropes are not casual mixes, but only at particular concentrations. EtOH/H2O is one of these: water boils at 100°C, as we all know. EtOH (pure!!!) boils at nearly 79°C, but the solution composed by 95% EtOH and 5% H2O bolis at 78,16 °C, slightly less than pure ethanol. So if you repeat simple distillations of a mixture water/ethanol you can reach at the most a composition 95 alcohol 5 water. You can't go over that concentration of alcohol. To get pure ethanol you have to work in a different way than dehydrating salts like MgSO4: you have to operate with an azeotropic distillation, making a mixture with a boiling point inferior than 95/5 alcohol/water. A such mixture is composed of ethanol/water/benzene (I don't remember the proportions). Anyway this mixture boils off below the 95/5.
So you have to distillate till you reach the 95/5, then yoiu have to add benzene in the necessary proportion to turn the azeotrope water/alcohol in a new azeotrope water/alcohol/benzene. You distill off this new azeotrope and what remains is "absolute" ethanol at 99%. Perhaps you can treat that with MgSO4 to get rid of a little more water.
Anyway the so-called "pure ethanol" (the 95%) is pretty expensive thanks to taxes, but the so-called "absolute ethanol" (the 99% one) is much more expensive and is used in small quantities only for particular works. If you use absolute ethanol for pseudo extraction is like feeding a donkey with biscuits.
I hope I have given a clear explanation of the problem.      

[kris_1108]

Thanks guys for all the info.

I should have informed more myself! - this is not for distillation (aaaargh sorry   )

Lets say you have a solution of 50mLs EtOH and 250mLs dH₂O. Can the EtOH be boiled out, leaving just the dH₂O behind?

[WizardX]

Azeotropic ethanol/water mixture is 78.2 oC and the mole fraction of H2O in the ethanol/water mixture is 0.096

What this means is 1000 mls (1Lt) of ethanol distilled at 78.2 oC has 1000mls x 0.096 water = 96 mls of water.

Binary Component Azeotropic Data.

[wareami]

Simple cooking culinary arts style teaches that alcohol can be cooked out of any dish containing alcohol without completely dehydrating the dish....so theoretically yes...the alky will boil off before the majority of h2o is boiled off.
And without knowing my ass from a hole in the ground....hehehe  so take it with a grain of salt..meth preferably  Distillation of heavier aliphatic hydrocarbons(AHC) in h2o will push the volatile AHC over first.
Alcohol evaps at a greater rate than h2o so I would think it too could be pushed over first during distillation leaving the non-volatile h2o behind.
I could be wrong here and I'm sure I'll hear about it if so.
I only offer my view in light of what wizardx posted is weigh over my head.....anvilstyle!
No Offense WizX...but that was all pure chemistry what you posted and something US tweekers are needing to get on the ball with here real quick.
In other words....thank you for that chart!
Right on time in my book!

[kris_1108]

Simple cooking culinary arts style teaches that alcohol can be cooked out of any dish containing alcohol without completely dehydrating the dish....so theoretically yes...the alky will boil off before the majority of h2o is boiled off.

Thanks, Ware! That was all I wanted to know. I want to do this instead of evaping the EtOH and then re-disolving in dH₂O. (Little experiment in progress.... will post again in succesfull.)