Kugelrohr
Encyclopedia
A Kugelrohr is a short-path vacuum distillation
apparatus typically used to distill relatively small amounts of compounds with high boiling point
s (usually greater than 300 °C) under greatly reduced pressure.
, as well as to allow the distillation to proceed at a lower temperature.
The apparatus consists of an electric heater with a digital thermostat, and two or more bulbs connected with ground glass joint
s. The compound to be distilled is placed in the last bulb. The other bulbs can be used to collect the distillates sequentially; when they are collecting the desired fraction, the bulb is cooled with ice to aid condensation. A motor drive is used to rotate the string of bulbs to reduce bumping
and give efficient distillation.
Image:Short path distillation apparatus.svg| A simple short path vacuum distillation apparatus can be used for bulb-to-bulb distillation.
Vacuum distillation
Vacuum distillation is a method of distillation whereby the pressure above the liquid mixture to be distilled is reduced to less than its vapor pressure causing evaporation of the most volatile liquid...
apparatus typically used to distill relatively small amounts of compounds with high boiling point
Boiling point
The boiling point of an element or a substance is the temperature at which the vapor pressure of the liquid equals the environmental pressure surrounding the liquid....
s (usually greater than 300 °C) under greatly reduced pressure.
Design
"Short path" refers to the short distance that the vapors of the distillate needs to travel, which helps reduce losses, and speed up collection of the distillate. Distilling under vacuum is used to prevent the compound being distilled from charring due to atmospheric oxygenOxygen
Oxygen is the element with atomic number 8 and represented by the symbol O. Its name derives from the Greek roots ὀξύς and -γενής , because at the time of naming, it was mistakenly thought that all acids required oxygen in their composition...
, as well as to allow the distillation to proceed at a lower temperature.
The apparatus consists of an electric heater with a digital thermostat, and two or more bulbs connected with ground glass joint
Ground glass joint
Ground glass joints are used in laboratories to quickly and easily fit leak-tight apparatus together from commonly available parts. For example, a round bottom flask, Liebig condenser, and oil bubbler with ground glass joints may be rapidly fitted together to reflux a reaction mixture...
s. The compound to be distilled is placed in the last bulb. The other bulbs can be used to collect the distillates sequentially; when they are collecting the desired fraction, the bulb is cooled with ice to aid condensation. A motor drive is used to rotate the string of bulbs to reduce bumping
Bumping (chemistry)
Bumping is a phenomenon in chemistry where liquids boiled in a test tube will superheat and, upon nucleation, rapid boiling will expel the liquid from the container....
and give efficient distillation.
See also
- DistillationDistillationDistillation is a method of separating mixtures based on differences in volatilities of components in a boiling liquid mixture. Distillation is a unit operation, or a physical separation process, and not a chemical reaction....
- Short path distillation
- Vacuum distillationVacuum distillationVacuum distillation is a method of distillation whereby the pressure above the liquid mixture to be distilled is reduced to less than its vapor pressure causing evaporation of the most volatile liquid...
Gallery
Image:Short path distillation apparatus.svg| A simple short path vacuum distillation apparatus can be used for bulb-to-bulb distillation.