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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.
Cold fingers are also used to condense vapors produced by sublimation in which case the result is a solid that adheres to the finger and must be scraped off, or as a cold-trap, where the liquid or solid condensate is not intended to return to the source of the vapor (often used to protect vacuum pumps and/or prevent venting of harmful gasses).
Short-path vacuum distillation apparatus with vertical condenser (cold finger), to minimize the distillation path; 1: Still pot with stirrer bar/anti-bumping granules 2: Cold finger – bent to direct condensate 3: Cooling water out 4: cooling water in 5: Vacuum/gas inlet 6: Distillate flask/distillate.
A Likens-Nickerson apparatus with a PTFE stopcock and water-jacket condenser in addition to the cold finger condenser. A round-bottom boiling flask with ground glass joints are affixed to either side of the apparatus with Keck clips. The unusually shaped Likens-Nickerson apparatus uses two boiling flasks.
A simple short path vacuum distillation apparatus can be used for bulb-to-bulb distillation. 1: Still pot with stirrer bar/anti-bumping granules 2: Cold finger - Condenser with maximum surface to condense most of the vapour. 3: Cooling water outlet 4: cooling water inlet 5: Vacuum Adapter 6: Receiving Flask.
The form of the cooled surface often is a so-called cold finger which for very low-temperature sublimation may actually be cryogenically cooled. If the operation is a batch process, then the sublimed material can be collected from the cooled surface once heating ceases and the vacuum is released. Although this may be quite convenient for small ...
Experts say certain red flags can mean a bigger health issue is at play — for example, episodes of cold hands that are frequent, not easily reversible or are new in those ages 30 years and above ...
In vacuum applications, a cold trap is a device that condenses all vapors except the permanent gases (hydrogen, oxygen, and nitrogen) into a liquid or solid. [ 2 ] [ needs update ] The most common objective is to prevent vapors being evacuated from an experiment from entering a vacuum pump where they would condense and contaminate it.