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7.5: Suction Filtration

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    Suction filtration components: Nub on water aspirator, vacumm trap, and suction flask. Flow is from suction flask to vacuum trap and can flow out towards water aspirator or back to suction flask.
    Figure 7.1: Suction filtration vacuum trap apparatus.
    Table 7.5: Procedural summary for suction filtration.

    Clamp a side-armed Erlenmeyer flask.

    Connect thick-walled hosing from the side arm to a vacuum trap and the water aspirator.

    Place a vacuum sleeve on the Buchner (or Hirsch) funnel, then filter paper on the funnel so it arches downward.

    Turn on the aspirator.

    Add a few \(\text{mL}\) of the same solvent used in the flask to wet the filter. The solvent should drain with suction.

    Swirl the mixture to be filtered to dislodge the solid from the sides of the flask.

    With a quick motion, pour the slurry into the funnel portions.

    In some applications (e.g. crystallization), rinse with solvent:

    • Open the apparatus to the atmosphere, then turn off the aspirator.
    • Add a few \(\text{mL}\) of cold solvent to the filter paper.
    • Delicately swirl the solid in the solvent with glass rod.

    Apply suction again for a few minutes (repeat the rinse step if necessary).

    Dry the solid on a watch glass along with the filter paper, overnight if possible. The solid will flake off the paper when dried.


    This page titled 7.5: Suction Filtration is shared under a CC BY-NC-ND 4.0 license and was authored, remixed, and/or curated by Lisa Nichols via source content that was edited to the style and standards of the LibreTexts platform; a detailed edit history is available upon request.