Kugelrohr distillation.

[wolfx]

Maybe someone could explain a bit about the theory and
experimental setup used for Kugelrohr distillation.
What advantages does it has over standard vacuum distillation ?

[terbium]

The advantage is just that it is quick and easy (if you have the equipment) and will work well for things that solidify at room temperature. It is just a quick and easy distillation but it won't give the type of separation of liquids with close boiling points as a fractional distillation would. Auf Deutsch, kugelrohr just means bulb(and)tube.

[Osmium]

Kugelrohr distillation is good for distilling high boiling substances, and to separate tarry shit. When you have a high vac. you perform some kind of sublimation, meaning the substances will distill over below their true boiling points since the distances the molecules have to travel are pretty short (in the order of the mean free path lenght at that pressure and temp). By spinning the bulbs the evaporation takes place from a thin film, similar to a rotovap, so the components don't have to be at their boiling point for good evaporation. And since the vacuum employed is stong the molecules can quickly travel around without being slowed down too much by collisions with other molecules. This means they can quickly travel to the colder bulb, leaving substances which are less volatile behind.

[foxy2]

Sounds like an expensive setup, bummer
Shulgin seemed to be a fan of the ol Kugelrohr

Do Your Part To Win The War

[LaBTop]

Kugelrohr Distillation is particularly suited to the distillation of small amounts of liquids (20mg or more) and also the high vacuum distillation of high-boiling oils (up to 209) because of the very short distillation path. For fractionation, the boiling points should be about 20C to 30C apart; when multi-bulb tubes are used, the distillation can be repeatedly carried out in the same tube.
The oven consists of two borosilicate glass tubes mounted on a support which carries the iris-type closure. The inner tube is heated by means of a surface-coated electrically conductive layer and a temperature sensor controls the surface temperature so that residues in the bulbs will not rise above the indicated temperature. The outer tube acts as a heat insulator and as a guard for the hot inner tube.

The Kugelrohr bulb tubes are held in a support which has a vacuum stopcock and includes an electric drive unit which rotates the ball tube at 15rpm. This support is free to slide along a guide rail to enable the bulb tube to be inserted or removed from the oven. The control module provides an On/Off switch with indicator lights for power and heaters, a switch for the ball tube drive, temperature selection knob and analogue temperature display.

There are two types of Kugelrohr tubes consisting of a train of five fixed bulbs or of separate bulbs connected by ground-glass joints with a jointed tube at one end. During distillations all the bulbs, except that nearest the tube end, are slid into the oven. After distillation/fractionation the individual bulbs may be cut off or separated.

Specification:
Temperature range                 30 to 250C
Oven interior dimensions lxdia    200 x 50mm
Iris diaphragm aperture           5 to 50mm (lockable)
Drive unit speed                  15 rpm
Dimensions lxwxh                  300 x 330 x 300mm
Weight                            7kg
Electrical requirements           240V 400W 50Hz

Price: 1715 English Pounds.

WISDOMwillWIN

[LaBTop]

This simple setup (3 bulbs 10ml+flask 50/100ml+vacuum outlet) costs ~$120.

Just to proof that there's always a cheaper way.

WISDOMwillWIN

[foxy2]

Do Your Part To Win The War

[Osmium]

Still wondering how they make the vacuum connection. Similar to rotovaps?

[terbium]

The (Kontes brand ?) glassware is nice but you still need a heating chamber and also a method of rocking the apparatus to prevent bumping. Aldrich used to sell a simple, cheap apparatus; perhaps they still do. As I remember with the old Aldrich device the kugelrohr was rocked (rotated) back and forth with a range of less than 180° so you didn't need a rotating vacuum seal, just loop of the vacuum tubing hanging free.

[wolfx]

A bit late, but anyway I would like to thank everybody that
contributed to this thread, it was very interesting and also
very instructive.

[ClearLight]

  The wonderful grand wizard of p's and t's  was telling me on a flight back from mexico, that he cobbled together his own kugel by taking the windshield wiper motor off a car and using it to rock the material back and forth, used a 100 watt light bulb with a dimmer under one bulb and applied the vacuum to the receiving bulb, said he spent about $20.00 on building it and was able to distill 1 ml samples with no loss!

 another gift to us all from the good Dr.


Infinite Radiant Light - THKRA