Lab Techniques

1
Lab Techniques

• Filtering

2
Gravity Filtration

• The correct way to set up for a gravity
  filtration is shown here in the photo.
• Note that the tip of the funnel is touching the
  side of the beaker to reduce splashing.

3
Filter Paper

• The filter paper used in Gravity Filtration comes
  as a circle and requires folding to fit into the
  funnel.
• Fold the circle in half as shown in 2. Then in
  half again as shown in 3.
• After step 3. tear off a small corner of one side
  of the paper.
• Open the paper into a cone shape with torn edge
  next to the glass and position it in the funnel.

4
Vacuum Filtration

• Always use a lab stand and clamp to hold the
  filter flask securely.
• A vacuum hose fitted with a plastic connector is
  used to connect the filter flask to a water
  aspirator.
• The water tap is turned on full.
• Water rushing past the orifice creates the vacuum.

Vacuum Filtration Setup
Filter paper sits in the bottom of the buchner
funnel and collects any solid material. No
Folding is required
5
Filtering with Ceramic Crucibles

• This form of vacuum filtration is used for
  quantitative analysis.
• Ceramic crucibles and a rubber adapter are used
  to collect the precipitate.
• The crucible and precipitate are dried in an
  oven,
• cooled in a desicooler containing dessicant,
• then weighed to a constant weight.