Vacuum filtration

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Vacuum filtration or suction filtration is a fast filtration technique used to separate solids from liquids using the difference of pressure between the flask and outside atmosphere as filtration force.

Setup

Equipment

Operation

  • Connect the vacuum filtering setup;
  • Turn on the vacuum pump or open the water tap for the aspirator;
  • Stir the suspension and then pour it in the Büchner funnel;
  • Wash the flask/beaker with water/solvent, stir then pour it in the funnel, then repeat at least 3 times;
  • The vacuum should continue until the last drop of solvent falls in the flask;
  • Keep the vacuum on for a few minutes, to remove as much solvent as possible, and the solid becomes semi-dry;
  • Turn off the vacuum pump and then remove the funnel to collect the suspension;

Tips

  • If the solvent is extremely volatile or corrosive, use a vacuum flask with inlet tube or a cold trap to prevent the hazardous vapors from reaching the pump and damaging it;

Safety

Always inspect the glassware before working with vacuum for any defects/cracks, to prevent an implosion.

References

Relevant Sciencemadness threads