Cold finger
Appearance
sublimation
. The raw product (6) is in the bottom of the outer tube (4) which is heated (7) while under vacuum (through side-arm 3). The sublimated material collects (5) on the cold finger proper, cooled by a coolant (blue) circulated through ports 1 and 2.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. The device usually consists of a chamber that a coolant fluid (cold tap water, or perhaps something colder) 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).[1]
Typically a cold finger is used in a
Dimroth condenser, for example. When used as a condenser in a rotary evaporator, cold fingers can be cooled to a lower temperature of −78 °C (dry ice), compared with water condensers that can be cooled to −40 °C (ethylene glycol
/water mixture). The lower temperature achieved reduces the quantity of volatile material exhausted into the air.
Media
-
A cold finger which includes a vacuum outlet.
-
Dark green crystals of nickelocene, freshly sublimed on a cold finger.
References
- ISBN 0070700958.
- ISBN 978-1118875780.