File:Image from page 31 of "Practical methods of organic chemistry" (1901) (14585145327).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: the more in-soluble compound will crystallise out, unac-companied by any of the other compound ;the crystals are filtered off, and the solutionfurther evaporated. If the crystallisation ofthe two fractions be repeated a second time,a complete separation will be effected. Forseparating a mixture of this kind, speciallyconstructed apparatus — the so-called ex-traction apparatus — may be employed, theuse of which possesses the advantage overthe method of simple heating, that muchsmaller quantities of the solvent are required.An apparatus of this kind is represented inFigs. 6 and 7. To a wide glass tube d isfused a narrow tube which acts as a siphon,bent as in Fig. 7. This portion of theapparatus is surrounded by a glass jacket b,narrowed at its lower end. This is con-nected with the flask that is to contain thesolvent. A cork bearing a reflux condenser—a ball condenser is convenient — is fitted in the opening at theupper end of the jacket. A shell of filter-paper is next prepared

Text Appearing After Image: Fig. 6. Fig. 7. CRYSTALLISATION 13 in the following manner : Three layers of filter-paper are rolledaround a glass tube with half the diameter of the inner tube d.One end of the roll must extend somewhat beyond the edge of theglass tube ; this is turned over and securely fastened with thread.To preserve the form of the roll, thread is loosely wound around itsmiddle and upper portion. The length of the roll is such that itextends 1 cm. above the highest point of the narrow siphon-tube.In the shell is placed the mixture of the easily soluble and diffi-cultly soluble substance to be extracted; the upper end is closedby a loose plug of absorbent cotton. The flask a, containing thesolvent, is now heated on a water-bath or over a free flame, accord-ing to the nature of the solvent. The condensed vapours drop fromthe condenser into the shell, dissolve the substance, filter throughthe paper, and fill the space between shell and inner glass tube.As soon as the liquid has reached the highest po

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