Buchner Funnel

Clamp the thick-walled Buchner flask in place on a retort stand to prevent the vacuum tubing from pulling it over. Insert the porcelain Buchner funnel with its rubber adapter into the flask.

Connect the vacuum tubing from the flask sidearm to the vacuum tap. Select appropriately-sized filter paper (5 cm for this funnel) and place two layers into the Buchner funnel.

Wet the filter papers with a small amount of the solvent (acetone in this case) to form a seal against the funnel bottom. Turn on the vacuum to pull the filter paper firmly into place.

Swirl the flask containing the magnesium sulfate suspension to resuspend solids, then quickly pour approximately one-third of the mixture into the Buchner funnel. The vacuum will pull liquid through while retaining solids.

Add additional portions of solvent to the funnel and allow them to filter through. Repeat the washing process multiple times until the filtered solvent runs clear, removing all impurities from the solid residue.

Disconnect the vacuum tubing from the flask sidearm before switching off the vacuum to prevent back-siphoning. Turn off the vacuum tap.

Review other vacuum filtration options including Hirsch funnels for small amounts, sintered glass funnels for fine solids that can be scraped without damage, and Gooch funnels useful for analytical chemistry applications.