Condenser (laboratory)
In distillation, a mixture is heated until the more volatile components boil off, the vapors are condensed, and collected in a separate container.
The simplest and oldest condenser is just a long tube through which the vapors are directed, with the outside air providing the cooling.
More commonly, a condenser has a separate tube or outer chamber through which water (or some other fluid) is circulated, to provide a more effective cooling.
In professional laboratories, condensers usually have ground glass joints for airtight connection to the vapor source and the liquid receptacle; however, flexible tubing of an appropriate material is often used instead.
The condenser may also be fused to a boiling flask as a single glassware item, as in the old retort and in devices for microscale distillation.
The water-cooled condenser, which was popularized by Justus von Liebig, was invented by Weigel, Poisonnier, and Gadolin, and perfected by Göttling, all in the late 18th century.
[2] Several designs that are still in common use were developed and became popular in the 19th century, when chemistry became a widely practiced scientific discipline.
Therefore, the primary consideration in the design or choice of a condenser is to ensure that its inner surface is below the liquid's boiling point.
This concern can be addressed by increasing the area of the condensation surface, by making the wall thinner, and/or by providing a sufficiently effective heat sink (such as circulating water) on the other side of it.
Additional considerations apply if the gas inside the condenser is not pure vapor of the desired liquid, but a mixture with gases that have a much lower boiling point (as may occur in dry distillation, for example).
The countercurrent condensers are intended to return the liquid toward the source of the vapor, as required in reflux and fractional distillation.
Straight tube condensers are no longer widely used in research laboratories, but may be used in special applications and simple school demonstrations.
It is named after Justus von Liebig,[6][7][8][9] who perfected an earlier design by Weigel[10] and Göttling[11] and popularized it.
The vapor is meant to condense on the rod and drip down from the free end, and eventually reach the collecting vessel.
Cold fingers are also used to condense vapors produced by sublimation in which case the result is a solid that adheres to the finger and must be scraped off, or as a cold-trap, where the liquid or solid condensate is not intended to return to the source of the vapor (often used to protect vacuum pumps and/or prevent venting of harmful gasses).
[21] It consists of a large water-cooled finger tightly fitted inside a wide cylindrical housing.
Each "finger" is created by melting a small section of the wall and pushing the soft glass inwards.
[24] These floating glass stoppers act as check valves, closing and opening with vapor flow, and enhancing vapor-condensate mixing.
Arriving at space (3), vapor is then directed via a distillation head (glass branching adapter) to cooling and collection.
Its main component is a tube filled with small objects to increase the surface area and the number of theoretical plates.
Alternatively, a closed system may be used, in which the water is drawn by a pump from a tank, possibly refrigerated, and returned to it.
Air with forced circulation can be effective enough for situations with high boiling point and low condensation rate.
Conversely, low-temperature coolants, such as acetone cooled by dry ice or chilled water with antifreeze additives, can be used for liquids with low boiling point (like dimethyl ether, b.p.
