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A Kugelrohr ( German for "ball tube") is a short-path
vacuum distillation Vacuum distillation is distillation performed under reduced pressure, which allows the purification of compounds not readily distilled at ambient pressures or simply to save time or energy. This technique separates compounds based on differences i ...
apparatus typically used to distill relatively small amounts of compounds with high
boiling point The boiling point of a substance is the temperature at which the vapor pressure of a liquid equals the pressure surrounding the liquid and the liquid changes into a vapor. The boiling point of a liquid varies depending upon the surrounding envi ...
s (usually greater than 300 °C) under greatly reduced pressure.


Design

" Short path" refers to the short distance that the vapors of the distillate need to travel, which helps reduce loss and speed up collection of the distillate. This type of distillation is generally performed under vacuum to prevent the compound from charring due to atmospheric
oxygen Oxygen is the chemical element with the symbol O and atomic number 8. It is a member of the chalcogen group in the periodic table, a highly reactive nonmetal, and an oxidizing agent that readily forms oxides with most elements as well ...
, as well as to allow the distillation to proceed at a lower temperature.Kugelrohr Distillation Apparatus
at the Buchi company website, accessed 15 Nov 2006.
The apparatus consists of a tube furnace or other electric heater controlled by a thermostat, and two or more bulbs connected with
ground glass joint Ground glass joints are used in laboratories to quickly and easily fit leak-tight apparatus together from interchangeable commonly available parts. For example, a round bottom flask, Liebig condenser, and oil bubbler with ground glass joints ma ...
s. The compound to be distilled is placed in the terminal bulb. The other bulbs can be used to collect the distillates sequentially, when the desired fraction is being collected the bulb is cooled with water or ice to aid condensation. A motor drive is often used to rotate the string of bulbs to reduce bumping, give even heating, and increase the surface area for evaporation.


See also

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Distillation Distillation, or classical distillation, is the process of separating the components or substances from a liquid mixture by using selective boiling and condensation, usually inside an apparatus known as a still. Dry distillation is the heating ...
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Short path distillation Short-path distillation is a distillation Distillation, or classical distillation, is the process of separating the components or substances from a liquid mixture by using selective boiling and condensation, usually inside an apparatus known ...
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Vacuum distillation Vacuum distillation is distillation performed under reduced pressure, which allows the purification of compounds not readily distilled at ambient pressures or simply to save time or energy. This technique separates compounds based on differences i ...


References


Gallery

Image:Short path distillation apparatus.svg, A simple short path vacuum distillation apparatus can be used for bulb-to-bulb distillation. 1: Still pot with stirrer bar/anti-bumping granules 2: Cold finger - Condenser with maximum surface to condense the most of the vapour. 3: Cooling water outlet 4: cooling water inlet 5: Vacuum Adapter 6: Receiving Flask. {{Distillation Distillation Laboratory equipment Laboratory techniques