Gravity Filtration:

Gravity filtration is a method used to separate a supernate, (liquid), from a precipitate, (solid). It is the preferred method when the solid material remains as a suspension in solution and the liquid can not be decanted, and the solid and liquid can not be separated by vacuum filtration due to the size of the particles.

There are several ways to arrange a gravity filtration, either with a glass funnel and filter paper or with a Buchner funnel and filter paper.

        

The above images depict two possible arrangements for gravity filtration with filter paper and a glass funnel. The filter paper has been prepared by fitting it into a cone. This can also be done by using a plastic funnel with filter paper.

In this figure a Buchner funnel is used to set into a beaker. The filter paper is half omitted on the left, and instead of being folded is simply put into the funnel above the holes flat.

It is important in this arrangement to wet the paper before adding the mixture to be filtered so the filter paper will remain in place during the filtration.