Slit sieve funnel

The chief disadvantages of a Buchner funnel for filtration are (i) it is impossible to see whether the underside of the perforated plate is perfectly clean, and (ii) the larger sizes are top heavy. The first drawback is absent in the Jena slit-sieve funnel (Fig. 11,1, 7,/) this is an all-glass funnel provided with a sealed-in transparent plate, perforated by a series of angular slots, upon which the filter paper rests. The sintered glass... 

For the suction filtration of small quantities of solid (less than 5g) contained in a small volume of liquid, a small conical Buchner funnel, known as a Hirsch funnel, is employed (see Fig. 2.43(h)) the filtrate is collected either in a small filter flask or in a test tube with side-arm, the arrangement being illustrated in Fig. 2.43(f). A small sintered funnel, or a slit-sieve funnel may also be employed. The procedure for filtration is similar to that already given for the Buchner funnel. 

For a large quantity of precipitate, a small Buchner funnel (b in Fig. II.9, shown enlarged for the sake of clarity) is employed. This consists of a porcelain funnel in which a perforated plate is incorporated. Two thicknesses of wellfitting filter paper cover the plate. The Buchner funnel is fitted into the filter flask by means of a cork. When the volume of liquid is small, it may be collected in a test-tube placed inside the filter flask. The Jena slit sieve funnel, shown in c, is essentially a transparent Buchner funnel its great advantage over the porcelain Buchner funnel is that it is easy to see whether the funnel is perfectly clean. 

A Pyrex slit sieve funnel, with 65 mm disc, is available commercially. 

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