File:Image from page 72 of "Practical methods of organic chemistry" (1901) (14585157527).jpg

Identifier: practicalmethods00gatt Title: Practical methods of organic chemistry Year: 1901 (1900s) Authors: Gattemann, Ludwig. [from old catalog] Subjects: Publisher: [n.p.] Contributing Library: The Library of Congress Digitizing Sponsor: The Library of Congress

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Text Appearing Before Image: in general. When filtering very small quantities of a liquid, atest-tube is placed in the filter-flask, as is represented in Fig. 36. The suction surface may be increased by placing a so-calledfilter-plate of glass or porcelain in the funnel (Fig. 37). If afilter-plate is used, the filter-paper should be of two thicknesses.Upon the plate is first placed a round filter of exactly the samesize as the plate, and upon this another round filter, the edge ofwhich projects about 2-3 mm. beyond that of the plate. The Btichner funnel is indispensable in working with organicsubstances. In consequence of its large suction surface, a veryrapid filtration is possible. In the filtration of large quantitiesof substance it should always be used (Fig. 38). FILTRATION 53 A double filter (described above) may be used in this, but inmost cases a single filter is sufficient. Since the Btichner funnelsare made of porcelain, and consequently are opaque, they must becarefully cleaned immediately after using.

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