A condenser is a glass tube which is used in the laboratory to cool hot gases which then turn to liquids. The tube is circular and long with another, smaller tube, inside. The hot gas passes through the inner tube and cold tap water passes through the bottom of the outer tube and out of the top. Making sure that the tube is always full of cold water enables cooling to be much quicker.
One use for a condenser is in distillation, when hot vapours need to be cooled and turned back to liquid. It is also used in reflux to ensure that the solvent does not boil away.
It is imperative that all apparatus is thoroughly washed and dried before being assembled. In order to prevent the escape of vapour, all corks should be fitted securely especially when distilling a flammable mixture.