Vacuum Filtration

The procedure of vacuum filtration

1. Fit the Buchner funnel to a suction flask.
2. Connect the side arm of the flask to the source of vacuum.  It can be a  water aspirator or aspirator pump which is located on the shelf above the lab bench.  Each desk has a valve for attaching the vacuum hose to your filter flask.  The lab instructor will turn these pumps on.  The water faucet, which provides water to the aspirator pump, is labeled.  Please do not use this faucet and do not change the flow rate!  Please keep your vacuum valve closed when not in use in order to keep the vacuum at other valves as low as possible.  You should not employ the vacuum filtration for gelatinous precipitates because the pressure differential forces the particles to the pores the filter paper, clogging them and the liquid can not pass through.
3. Put the paper in the Buchner funnel, and wash it with the solution.
4. At first, decant the liquid phase into the funnel and then add the precipitate.
5. Wash the precipitate by adding small amounts of wash liquid over the surface of the precipitate, allowing the liquid to be drawn through the solid slowly with the vacuum.
6. Dry your precipitate by drawing a current of air through it.