File:Image from page 75 of "Practical methods of organic chemistry" (1901) (14585159837).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: he cell from which the wash water canpermeate the precipitate in all directions. If the precipitate islarge enough to completely fill the interior space of the cell, itforms a solid cake that can be removed without difficulty. Butif the precipitate is small, and it is desired to obtain it, the glasstube is withdrawn from the rubber ring, the contents of the cell, generally half-fluid, arepoured into a beaker,the cell taken apart, andthe precipitate adheringto the sides scraped offwith a spatula. By fil-tering with suction acomplete separation ofthe liquid and precipi-tate is effected. If it isdesired, to filter larger quantities of a precipitate than can con-veniently be done in a single cell, two cells connected by a Y-tubemay be used. Filtering through Muslin. — Precipitates which are not toofinely divided may be filtered off through a filter-cloth (muslin)stretched over a wooden frame (filter-frame) (Fig. 42). A squarepiece of muslin or linen, after being thoroughly moistened, is

Text Appearing After Image: Fig. 42. FILTRATION 57 fastened on the four nails of the frame is such a way as to causea shallow bag in the middle. The frame is placed over a dish ofthe proper size and the liquid to be filtered is poured on thecloth and generally filters rapidly through it. If it is desired afterwashing the precipitate to press it out, the cloth is taken fromthe four corners, folded together, and squeezed with the hands.The precipitate may be further dried, by tying up the openingof the bag with twine, and then pressing it out carefully under ascrew-press. 58 GENERAL PART HEATING UNDER PRESSURE Sealed Tubes. Method of Filling. — If it is desired to inducea reaction between two substances at a temperature above theirboiling-points, .they are generally heated in sealed tubes. If aquantitative determination is not to be made, if the substancesto be heated do not attack the glass or generate no gases, and ifthe heating is not to be high, soft glass tubes may be used. Butgenerally, and in quantitative

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