Vacuum Filtration

Vacuum filtration and gravity filtration are similar since they can both be used to separate a solids from liquids. The diagram at right illustrates the vacuum filtration process.

The aspirator, at right, produces a vacuum in the water bottle trap and the filtration flask. This vacuum draws liquid downward through the filter paper leaving behind the solid product. The liquid trapped in the filter flask is often referred to as the mother liquor.

Note the differences between the pieces of tubing in the water bottle trap. The long tube is always attached directly to the filter flask. The small tube is always attached to the aspirator. This arrangement insures that if some small amount of the mother liquor is accidentally transferred from the filter flask into the water bottle trap, the liquid will be trapped in the water bottle. This protects the public water/sewer systems from contamination that would occur if the liquid had reached the aspirator.