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.
Contents
Setup
Equipment
- Aspirator or vacuum pump
- Vacuum flask with inlet tube (optional) or cold trap
- Rubber tubes
- Conical rubber seal
- Büchner flask
- Büchner funnel (fritted or perforated plate with filter paper) or Hirsch funnel
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 a potential implosion.
