Funnel/Filter Paper
Gravity filtration involves the use of a conical funnel and a circular piece of filter paper. The filtration proceeds most efficiently when the stem of the funnel has a continuous column of liquid with no air bubbles. A funnel is constructed so that the angle of the cone of the funnel (60o, see below) will accomodate filter paper when it is folded exactly in half twice. This means the paper can make close contact with the funnel when the paper is folded in that way. In order to insure that the paper makes close contact with the funnel, particularly at the top, we fold the paper so that the angle of the cone that it forms is slightly larger than 60o.
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