Sciencemadness Discussion Board

Vigreaux column disadvantages

TinSandwich - 2-5-2016 at 11:10

I'm about to buy a distillation apparatus :) but I'm having some trouble making up my mind. Most kits I have found seem to include a vigreaux column, I don't plan on doing any fractional distillation right now but it might come in useful one day and it's about the same price with or without it. The only problem is that the column is non-removable, it is attached to the still head and if I buy it any distillation I'll ever do will have to go trough it.

My question is are there any reasons why this might be a problem? For example is fractional distillation slower than normal distillation or does it require more heating?

Metacelsus - 2-5-2016 at 11:26

Quote: Originally posted by TinSandwich  
For example is fractional distillation slower than normal distillation or does it require more heating?


Yes, and yes. Cleaning out the head might also be a pain if you can't remove the column.

[Edited on 5-2-2016 by Metacelsus]

arkoma - 2-5-2016 at 11:30

I'd look for a different kit. This one is only $131.

aga - 2-5-2016 at 11:53

Great find arky ! Wish i'd bought that one much earlier.

A vigreux adds very little time to the distillation, whilst adding a lot more separation, so definitely worth having.

The kit in that link has all you'll need for quite a while.
Liebig, Graham, Allhin condensers + a Vigreux.

It's a steal for the 2 & 3 neck flasks alone !

XeonTheMGPony - 2-5-2016 at 12:12

That is a very good kit! have to see if they have it in 20/24

CharlieA - 2-5-2016 at 12:27

According to Fieser, Research Techniques in Organic Chemistry, a typical Vigreaux column, 50 cm, operating at a reflux ratio of 5:1 has about 5 theoretical plates. This will give a pure distillate (95% pure for 2 compounds boiling 30 deg C apart. For a good separation of 2 compounds boiling 10 deg C apart, you need 22 plates.

My conclusion is that a Vigreaux column may help prevent liquid from the pot bumping over into the distillate, but is not good for much else.

@Metacelsus is right about the head/column combo being a pain to clean.

Texium - 2-5-2016 at 12:31

Quote: Originally posted by XeonTheMGPony  
That is a very good kit! have to see if they have it in 20/24
You mean 24/40? I've never heard of 20/24 before...

@CharlieA: Yes, Vigreux columns are certainly not the most efficient, but if you don't mind doing a few distillations for one separation and control the temperature very carefully, separating two compounds that have a 10ºC or smaller difference in BP is certainly feasible.

JJay - 2-5-2016 at 12:49

Vigreux columns are certainly useful. I don't think they are as generally useful as Hempel columns, but they are more convenient to use and do work well for certain distillations that need to be performed frequently (e.g. water and ethanol). I've actually seen people pack Vigreux columns before, but I don't think it's a good idea really.

Depending on your starting concentrations, you may already have several theoretical plates in your separation. Multiple distillations will give you more plates.

Dr.Bob - 2-5-2016 at 12:53

The other use for a Vigreux column is using it as an air condenser for refluxing higher boiling temperature solvents. I do that often now, to avoid issues with overnight water leaks or drops in pressure. I have seen so many chemists run a reaction overnight and come back to a black tar when their water slows down or shuts off or the hose pops off and also floods the lab. Even for shorter time frames like a few hours, I often use them.

But I would not buy a kit with one piece vigreux/head as my only dist head, that is too fixed and very hard to clean or fit into some reactions. I have one or two of them, but they are rarely used, and I don't need a vigreux column in many cases. For most chemists, they provide sufficient purification in distillations. Few people here are distilling isomers apart or trying to do 99.99% purity work. Most of my distillations are a quick and easy way to remove solids, salts, and bulk impurities.

XeonTheMGPony - 2-5-2016 at 14:35

Quote: Originally posted by zts16  
Quote: Originally posted by XeonTheMGPony  
That is a very good kit! have to see if they have it in 20/24
You mean 24/40? I've never heard of 20/24 before...

@CharlieA: Yes, Vigreux columns are certainly not the most efficient, but if you don't mind doing a few distillations for one separation and control the temperature very carefully, separating two compounds that have a 10ºC or smaller difference in BP is certainly feasible.


Yes I am suffering from the effects of heat here, brain doesn't work so good once the frost melts! goat I need an air conditioner! That or bigger freezer.

As to the OP yes they are useful but not in that iteration.

[Edited on 2-5-2016 by XeonTheMGPony]

TinSandwich - 3-5-2016 at 03:25

Thanks for all of your answers! I'll keep my eyes open, every couple of days there's something new on ebay. I was thinking of getting a basic kit with no vigreaux, a liebig condenser and a 1000ml flask

arkoma - 3-5-2016 at 06:08

I've dealt with sam100086 SEVERAL times. Very good value for the money and prompt (less than ten days) shipping to the US.