Refluxing - Archive File

[megalomania]

10fingers
Frequent Poster
Posts: 411
From: USA
Registered: SEP 2000
posted 06-18-2001 03:24 PM
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Is refluxing the same as fractional distillation? Would you use a vigreux column for this process?
I was just reading a process for making ethanol fuel from corn. They describe how to make a reflux distillation column which can give you a high purity of alcohol,(95%) on one pass through. That's starting with a mixture of 90% water and 10% ethanol.
It seems this same system could also be used for separating nitromethane from hobby fuel. It also might work for distilling acetic acid to get all the water out. I have some app. 80% acetic acid and I have distilled from sulfuric acid three times under vacuum and it still has water in it.


John456
Frequent Poster
Posts: 105
From:
Registered: MAR 2001
posted 06-18-2001 03:45 PM
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Refluxing is when you boil a liquid and condense it back into the same flask. Its used in most organic syntheses that take hours or days to perform. All you have to do is put a condenser in the top joint of a flask and run cold water through the condensor throughout the procedure. If you want to protect your reaction from water you put a drying tube filled with some drying agent (Calcium chloride is a popular one) at the top of the condensor.

[vulture]

I just install my liebig cooler vertically without the destillation bend. However, I did once operate it vertically using the 2 bends to create a 180C turn which went into the distilling flask.
This way you can achieve a higher separation between closely boiling liquids.

It should not be used this way for distilling acids like HNO3 that decompose because you'll need to heat much more than during a normal destillation. That's also why a vigreux column shouldn't be used for distilling HNO3.

I've got pics (B&W) if anybody is interested.

BTW, the spot where the condensing starts should maximally reach 1/3 of the total length of your cooler if you leave it open on the topside! Certainly with flammable or harmful compounds!

Refluxing is not the same as fractional destillation. Fractional destillation separates several boiling fractions by rotating a special piece of glass with multiple flasks connected to it.
The fractions are collected by boiling point.