Condenser (laboratory)
In a laboratory, a condenser is a piece of laboratory glassware used to cool hot vapors or liquids. A condenser usually consists of a large glass tube containing a smaller glass tube running its entire length, within which the hot fluids pass.
The ends of the inner glass tube are usually fitted with ground glass joints which are easily fitted with other glassware. The upper end is usually left open to the atmosphere, or vented through the a bubbler on a Schlenk line, or a drying tube to prevent the ingress of water or oxygen.
The outer glass tube usually has two hose connections, and a coolant (usually tap water or chilled water/anti-freeze mixture) is passed through it. For maximum efficiency, the cold water always enters through the bottom fitting, and exits through the top fitting. Multiple condensers may be connected in series, but a high flow rate must be maintained.
Applications
Condensers are often used in reflux, where the hot solvent vapors of a liquid being heated are cooled and allowed to drip back. This reduces the loss of solvent allowing the mixture to be heated for extended periods.
Condensers are used in distillation to cool the hot vapors, condensing them into liquid for separate collection. For fractional distillation air condenser or Vigreux condenser is usually used to slow the rate at which the hot vapors rise, giving a better separation between the different components in the distillate.
For microscale distillation, there are commercially available one-piece apparatus which include the "pot", the Claisen head, and the condenser fused into one-piece. This reduces the hold-up volume, and obviates the need for ground glass joints preventing contamination by grease and air leaks.
Air condenser
An air condenser is the simplest sort of condenser. There is only one tube, and the heat of the fluid is conducted to the glass, which is cooled by air.
Vigreux condenser
A Vigreux condenser is a modification of the air condenser; multiple glass protrusions are used to increase the surface area, allowing better heat exchange.
Liebig condenser
This is the most basic water-cooled design. The inner-tube is straight, making it cheaper to manufacture.
Though named after the German chemist Justus Baron von Liebig, he cannot be given credit for having invented it because it was already in use for some time before him. However, it is believed that the apparatus was made popular by him.
The true inventors, all of them making the discovery independently, and the year of the invention were the German chemist Christian Ehrenfried Weigel in 1771, French scientist, P. J. Poisonnier, in 1779 and the Finnish chemist Johan Gadolin in 1791.
Liebig himself incorrectly attributed the design to the German pharmacist Johann Göttling who had made improvements to the Weigel design in 1794 [1].
The Liebig condenser is much more efficient than a simple retort due to its use of liquid cooling. Water can absorb much more heat than the same volume of air, and its constant circulation through the water jacket keeps the condenser's temperature constant. Therefore a Liebig condenser can condense a much greater flow of incoming vapour than an air condenser or retort.