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Laboratory Practices
Figure 2
General Purpose Distillation Apparatus
2.5 Filtration
2.5.1 Vacuum Filtration
Laboratory Practices
Page 18
Filtration separates particulates from an aqueous sample. It uses a porous
medium that retains particulates but allows liquids to pass through. It is useful
for removing turbidity (which may interfere in colorimetric analyses) from
water samples.
Two methods of filtration are most frequently used: vacuum filtration and
gravity filtration.
Vacuum filtration uses both suction and gravity to draw the liquid through the
filter. An aspirator or vacuum pump is used to create suction (see Figure 3).
It is faster than gravity filtration.
To filter using a vacuum:
1. Use tweezers to place a filter paper into the filter holder.
2. Place the filter holder assembly in the filtering flask. Dampen the filter with
deionized water to ensure adhesion to the holder.
3. Position the funnel housing on the filter holder assembly.
4. While applying a vacuum to the filtering flask, transfer the sample to the
filtering apparatus.
5. Slowly release the vacuum from the filtering flask and transfer the solution
from the filter flask to another container.
5940022LabPrac.fm
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