mdp2p temperature range

[hest]

I think that the best practical info is in the chemistry book's from the 50 and 60´s. By the way, wacumjaced collums are greth. I have a wacum jacked Vigreux collum, an it beats all my other collums (packed and non packed, but no wacumjacked). I don't think they are that ekspensive.

[lab_bitch]

It's a bubble plat column.  These are not as easily flooded as vigreaux columns are.  The trick to getting pure, fast safrole, is to vary your distillation rate throughout the process.  The beginning and end are crucial for purity, so you must go slow during these parts.  During the middle, however, you can crank it up full blast and it won't affect your purity one bit.  This is how I do it

1) Distill very slowly until the temp is 3C below your expected bp.
2) Distill very fast until the temp goes 2C above your expected bp.
3) Now distill very slowly until the temp goes 3C above your expected bp.

This way, you don't wasted time one the middle shit, just the two ends.

[Chromic]

There's only two factors in separation efficiency:

1) reflux ratio (how many drops fall back into the flask versus how many drops jump over into the receiving flask)

2) theoretical/actual plates

If the reflux ratio is extremely high (ie operating at total reflux), then the separation is as good as the theoretical plates indicate. If less, then the operating line steps off from the y=x line on the macabe-thiele diagram (vapor pressure of light component vs vapor pressure of heavy component). And of course, the reflux ratio is controlled by the heat loss on the column. For something like ethanol/water you want to remove a lot of heat, for something like safrole boiling at 200C you want to remove almost no heat.

[Osmium]

Another important factor is the amount of stuff going in and out of your column. The less the better from a separation efficiency standpoint.
I'm not fat just horizontally disproportionate.

[DiMethyl]

I thought we were not supposed to list sources? But now that the cat is out of bag I have a number of pieces of glassware with labglass printed on them. I think they come from Mexico. Works great for me. The Oldershaw column is going on my wish list.

[LaBTop]

Keyword: PATIENCE!

Simple logic: you choose the length of the vigreux column on a few data:
1. What are you trying to reflux, a high or low boiling substance.
2. Is your column insulated or not, and is it needed at all. High=yes , Low boiling=not
2a. Choose the best insulation material for high boiling stuff, the better the insulation, the more preciser your reflux separation in f.ex. a 1 to 5 Celsius reflux-traject.
3. If you have f.ex. 3 vigreux columns, 10, 20 and 40 cm, does the 40 cm allow you to receive sufficient flowrate in your receiving flask? If yes, use that one, if no, step down untill you have found the right one.

If you want to know really what's needed for calculating these things, which you can easily do by trial and error, then you have to read sticky threads and UTFSE.
And buy an Oldershaw column + the rest. LT/
WISDOMwillWIN

[Chromic]

If it's a boiling at a low temp w/high flow rate, say distilling multiple liters of ethanol at 78C... you might actually want a large column with external cooling. Take a look at:

https://www.thevespiary.org/rhodium/Rhodium/archive/still.pdf

If you're boiling at a medium temp or a low temp w/a low flow rate... you'd just want the column (eg distilling acetone, DCM, etc to reprocess them... not to be confused with stripping solvents, where you likely want no column...). Or perhaps if all the vapors are coming back as reflux, (say distilling PERC at ~120C with a 400mm column) you might want insulation (say, some pieces of fleece... or a vacuum jacketed column).

If you're boiling at a high temp with a low flow rate, you want VERY little cooling. Or else all of it will be returned as reflux, so you need good insulation. Say you're distilling safrole at 180C over a 200mm column. You want to wrap the column with something that insulates well and can withstand the temperature, say wrapping glasswool around your column. Alternatively, you can get a vacuum jacketed column.

Also, it should be noted that the type of packing is important too. Vigreux's acheive very few HETP compared to say steel wool in the same diameter/length. Although stainless steel wool is really good at doing its job... it won't stand up to all conditions (and has a higher hold up)... and cleaning has an influence on what column you use as well.

I hope that hasn't confused people. Basically you want enough insulation (occassionally cooling or heating) so you get a decent reflux ratio and that the column is efficient enough (length, diameter, and choice of packing) to see a clean separation between fractions.

[Chromic]

I'm a little confused as to why you would add stainless steel wool if you're getting too much reflux. A quick review:

Stainless steel wool is a packing material for the column. It's put inside of a hollow column. It's best suited for small diameter columns (<3") where raschig rings and other materials and glass indentations (such as on a vigreux) aren't efficient enough for the purposes desired. Raschig rings are used for medium sized columns... industrial-sized columns use stages with plates. Btw, you won't be able to get stainless steel wool to work with a vigreux (the indentations stop you from putting it thru) but you could use it with a liebig condenser (when the liebig condenser is used vertically as a column... not as a condenser... I hope that's was obvious).

Glass wool is for insulating the column if you're getting to much reflux. It's wrapped around the outside of the column. (most hardware stores carry it for wrapping pipes) Fleece is much easier to handle and I've found it to insulate even better to insulate than glasswool if you're distilling at a temperature where the fleece won't melt. Cotton is a really poor insulator, but works for higher temps as well.

Crumpled aluminum foil works some, but any of the other techniques is highly recommended.

Btw, if you only need to insulate part of your column to acheive a good reflux ratio, ensure it's the bottom part that is insulated.