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 a bubbler, 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. Normally a high flow rate is not necessary to maintain a cooling surface.
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, an air 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 apparatus which include the "pot", 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.
