Laboratory Practices
Laboratory Practices
5940022LabPrac.fm Page 19
Figure 3 Vacuum Filtration
Required Apparatus for Vacuum Filtration
Description Unit Cat. No.
Filter Discs, glass fiber, 47-mm ......................................................................................... 100/pkg...............2530-00
Filter Holder, membrane, 47-mm..................................................................................... each....................13529-00
Flask, filtering, 500-mL ...................................................................................................... each........................546-49
Pump, vacuum, hand operated........................................................................................ each....................28248-00
or
Pump, vacuum, portable, 115 VAC.................................................................................. each....................14697-00
Pump, vacuum, portable, 230 VAC.................................................................................. each....................28248-01
2.5.2 Gravity Filtration
Many of the procedures in this manual use gravity filtration. This requires
only filter paper, a conical funnel, and a receiving flask (see Figure 4). Gravity
filtration is better for retaining fine particles. The rate of filtration increases as
the volume increases in the filter cone, but never fill the cone more than
three-quarters full.
Note: Pretreatment using acid and heat is often necessary for metals testing. Filter paper will not
withstand such an environment; therefore, vacuum filtration with glass fiber filter discs is
recommended. Also, glass filter discs do not retain colored species like the paper filters do.
To filter using gravity:
1. Place a folded filter paper into the funnel.
2. Dampen the filter paper with deionized water to adhere it to the funnel.
3. Place the funnel into an Erlenmeyer flask or graduated cylinder.
4. Pour the sample into the funnel.
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