Cold finger

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 and is a type of cold trap.

Description

The device consists of an elongated chamber where a coolant lowers the temperature of the glass item. There are two models:

• First model uses a continuous stream of cooling fluid, such as cold tap water, or something colder
• Another model is a simple glass tube where a cold material, such as dry ice or dry ice/acetone is added

Cold fingers have a ground glass joint, which allows them to be fitted to a specially designed vacuum flask, which is then connected to a LN2 trap and a vacuum pump.

Availability

Cold fingers can be purchased from lab suppliers. Good quality cold fingers are a bit pricey, but since you need good quality glassware when working under vacuum, it's a good idea to avoid using cheap types and go for something better.

Projects

• Sublimation
• Purify air-sensitive compounds

See also

• Cold trap

References

Relevant Sciecnemadness threads

• Cold finger - how it works
• Coldfinger improvisations