Fine grain precipitates can be filtered only by applying filters with small pore size. Using thick filters makes the filtration process slower. To speed up the filtration, it is practical to use reduced (or elevated) pressure.
In the first experiment a filtration system was set up, consisting of a thick-walled Büchner flask and a porcelain Büchner funnel. A thick filter paper is placed on the Büchner funnel. Reduced pressure was generated using water-jet vacuum pump. Filtration was used for separating the green insoluble copper hydroxide carbonate (CuOH)2CO3 from water suspension.
In everyday life, for example, reduced (or elevated) pressure is used in four types of filters in modern cars:
1) An air filter is used to separate solid particles from the air required for the combustion of the fuel.
2) A fuel filter separates solid particles from fuel.
3) An oil filter is used to clean oil from solid particles.
4) A cabin air filter is used to clean incoming outside-air from dust.
In this experiment, the first three types of filters were shown and it was demonstrated how solid coffee particles can be separated from water by using a fuel filter.