Solvent Stills

SolventStills
A typical solvent still for bulk distillations.

Solvents used for the preparation and manipulation of sensitive compounds must be rigorously dried prior to use. This is traditionally achieved by refluxing the solvent over a suitable desiccant for several days under an inert atmosphere, followed by distillation. The solvent is then typically stored over activated molecular sieves or a potassium mirror in a sealed ampoule to ensure the solvent remains dry.

Common desiccants:

  • THF – Potassium or Sodium/Benzophenone
  • Diethyl Ether – Sodium/Benzophenone
  • Hexane – Sodium/Benzophenone + Triglyme
  • DCM – Calcium Hydride
  • Toluene – Sodium
  • Benzene – Sodium
  • Acetonitrile – Calcium Hydride

NaK, a sodium/potassium alloy that is liquid at room temperature, is also commonly used.

For further details of suitable desiccants and procedures for purifying solvents, consult the latest edition of Purification of Laboratory Chemicals.

Solvent purification systems are a popular and much safer option for drying solvents, but often require frequent maintenance and replacement of the activated alumina columns.