A cold finger is a piece of laboratory equipment that is used to generate a localized cold surface. It is named for its resemblance to a finger as is a type of cold trap.
Typically a cold finger is used in a sublimation apparatus, or can be used as compact version of a condenser in either reflux reaction or distillation apparatus.
The device usually consists of a chamber in which a liquid (typically cold tap water) can enter and leave. Another version involves filling the device with a cold material (examples: ice, dry ice or a mixture such as dry ice/acetone or ice/water).