Hach DR/700 Procedures Manual page 37

solution to pass through. This is especially helpful when sample
turbidity interferes with calorimetric analysis. Two general methods of
filtration are gravity and vacuum. Gravity filtration uses the force of
gravity to pull the sample though the filter paper. Vacuum filtration uses
the pressure difference created by either an aspirator or vacuum pump
plus the force of gravity to move the sample through the filter. Vacuum
filtration is faster than gravity filtration. Vacuum filter (see Figure 4) as
follows:
1. Place a filter paper into the filter holder.
2. Place the filter holder assembly in the filtering flask and wet 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 to
another container.
Figure 4 Vacuum Filtration
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