Folded filter paper

Filtration involves the separation of insoluble solid materials from a liquid. In this operation, the liquid passes through a porous barrier (sintered glass or filter paper) and the solid is retained by the barrier. The liquid can be made to pass through the barrier by gravity alone, in which case the procedure is called a gravity filtration. Alternatively, the liquid can be caused to pass through by a combination of gravity and air pressure. Such an operation is called a vacuum or suction filtration. A piece of filter paper and a conical glass funnel to support it are all that are required for gravity filtration.In order to maximize the rate at which the liquid flows through the filter paper, the paper should be folded as indicated by the steps shown below.The folded paper is then dropped into the funnel. The funnel is best supported in an iron ring, as shown in the figure. The material to be filtered is poured into the filter paper cone, in portions if necessary. ... Folding of filter paper for gravity filtration: (a) Fold the filter paper circle (11 cm diameter) in half. (b) Crease the half to divide it into eight equal pie-shaped sections; it is easiest to make the creases in the numerical order shown. (c) Turn the piece over and pleat it into a fan by folding each pieshaped section in half in the direction opposite to the previous creases. (d) Pull the two sides apart. [chem.wisc.edu/areas/organic/orglab/tech/filtration.htm]