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Magpie
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I don't know if a Vigreux column has enough "stages" to separate water and azeotropic ethanol. I was able to do this with an 8" long Hempel column
packed with a ss scrub pad, however. I supposed it depends on the length of the Viqreux
The single most important condition for a successful synthesis is good mixing - Nicodem
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aga
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Quote: Originally posted by Magpie  | | I don't know if a Vigreux column has enough "stages" to separate water and azeotropic ethanol. I was able to do this with an 8" long Hempel column
packed with a ss scrub pad, however. I supposed it depends on the length of the Viqreux |
wooo. Hempel Column.
more glassware to acquire ...
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blogfast25
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Well, exactly. Column height, operating conditions like reflux ratio (ratio of reflux stream to product stream), internal surface area of the column
and feedstock composition in terms of EtOH are the main variables that affect product composition.
There is no a priori reason to believe that in suitable conditions azeotropic EtOH cannot be achieved with a good Vigreux set up.
Hempel columns (packed columns) have their own set of problematics like potential column flooding for instance, which can limit the amount of reflux
achievable.
[Edited on 23-8-2014 by blogfast25]
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Magpie
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Kt5000 seemed to be a beginner at distillation who was looking for advice. I assumed that he would not know what length of Vigreux that is necessary
for this separation (I don't). My post was only meant as a warning that not just any fractionating set-up will separate azeotropic ethanol from
water. I then gave the conditions that I used which provided a successful result. It's a data point for him to consider.
I know Vigreux columns have their place. I don't own one and admit a prejudice against using one for any challenging distillation, which I consider
the above case to be as the boiling point difference is only 22°C (100-78). My college lab manual (Pavia et al) says the following regarding the
Vigreux:
"Vigreux columns are popular in cases where only a small number of theoretical plates are required. They are not very efficient (a 20-cm column
might have only 2.5 theoretical plates), but they allow for rapid distillation and have a small holdup (the amount of liquid retained by the column).
A column packed with stainless steel sponge is a more effective fractionating column than a Vigreux, but not by a large margin."
[Edited on 23-8-2014 by Magpie]
The single most important condition for a successful synthesis is good mixing - Nicodem
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aga
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Chill Mags.
No attack going on.
Bloggers is just a bit blunt and grumpy cos a student sterilised the pet hampster ...
... in an autoclave.
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Magpie
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Shame on him...everyone knows that for a hampster you use a microwave oven.
The single most important condition for a successful synthesis is good mixing - Nicodem
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aga
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Some recipies are better than others.
Personally i favour Turnip Surprise.
Surprised everyone, including the hampster.
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Fantasma4500
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orange skin!
then pour the destillate into some tall thin glass container and add some food colouring, it should only colour the water making it relatively easy to
seperate out the limonene, it should float on top
otherwise i recall some interesting compound was extracted from tomato paste
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confused
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is there any way to test the water content after ethanol distillation?
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blogfast25
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Density of the ethanol goes up with water content, as the density of pure EtOH is 0.789 and that of water 1.000. Towards the high end of EtOH content
that method becomes fairly insensitive though.
EtOH content in EtOH/water mixtures can be chemically determined by iodometry. Standardised acidified potassium dichromate is reduced by EtOH to Cr
(III). The remaining potassium dichromate is used to oxidise iodide to iodine and the iodine titrated with standardised sodium thiosulphate. Quite
laborious...
For very low levels of water Karl Fisher titrations would be called for.
[Edited on 24-8-2014 by blogfast25]
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kt5000
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| Quote: Originally posted by aga |
Bloggers is just a bit blunt and grumpy cos a student sterilised the pet hampster ...
... in an autoclave.
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I don't have an autoclave.. Microwave will have to do.
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Texium
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I believe that this was the
thread you were thinking of: Extraction of Lycopene
It does look interesting. It has a very nice color to it.
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