Soxhlet extractor

A Soxhlet extractor has three main sections: a percolator (boiler and reflux) which circulates the solvent, a thimble (usually made of thick filter paper) which retains the solid to be extracted, and a siphon mechanism, which periodically empties the condensed solvent from the thimble back into the percolator.

The solvent vapour travels up a distillation arm, and floods into the chamber housing the thimble of solid.

The condenser ensures that any solvent vapour cools, and drips back down into the chamber housing the solid material.

The thimble ensures that the rapid motion of the solvent does not transport any solid material to the still pot.

The removable holder/chamber is fitted with a small siphon side arm and, in the same way as for Soxhlet, a vertical condenser ensures that the solvent drips back down into the chamber which is automatically emptied at every cycle.

A schematic representation of a Soxhlet extractor:
  1. Stirrer bar
  2. Still pot (the still pot should not be overfilled and the volume of solvent in the still pot should be 3 to 4 times the volume of the Soxhlet chamber)
  3. Distillation path
  4. Thimble
  5. Solid
  6. Siphon top
  7. Siphon exit
  8. Expansion adapter
  9. Condenser
  10. Cooling water out
  11. Cooling water in