Image from page 26 of "Practical methods of organic chemistry" (1901) (14584910860)

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

Text Appearing Before Image:

k-walledfilter-flasks from being cracked by solvents of a high boiling-point,they are somewhat warmed before filtering by immersion in warmwater. Boiling nitrobenzene, aniline, phenol, and similar substances maybe filtered in the usual way through ordinary filter-paper. Choice of the Crystallisation Vessel.—The size and form of the CRYSTALLISATION 7 crystallisation vessel is not without influence upon the separationof the crystals. If a compound will crystallise out on simple cool-ing, without the necessity of evaporating a portion of the solvent,a beaker is used for the crystallisation. The shallow dishes knownas crystallising dishes are not recommended for this purpose,since they cannot be heated over a free flame, and further, thesolution easily creeps over the edge, involving a loss of thesubstance. Moreover, the crusts collecting on the edges are veryimpure, since, in consequence of the complete evaporation of thesolvent, they contain all the impurities which should remain dis-

Text Appearing After Image:

Fig. 3. Fig. 4. Fig. 5. solved in the mother-liquor. The beaker is selected of such asize that the height of the solution placed in it is approximatelyequal to the diameter of the vessel, which is thus about one-halfto two-thirds filled. Heating after Filtration. — Many compounds crystallise out inthe beaker during filtration. The crystals thus obtained are neverwell formed, in consequence of the rapid separation; therefore,after the entire solution has been filtered, it is heated again untilthe crystals have redissolved, and is then allowed to cool as slowly 8 GENERAL PART as possible without being disturbed. In order to protect thesolution from dust as well as to prevent it from cooling too rapidly,the vessel is covered first with a piece of filter-paper and thenwith a watch-glass or glass plate. The paper is used to preventdrops of the solvent formed by the vapours condensing on the coldcover-glass from falling into the solution, by which the crystallisa-tion would be disturbed.

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1901

Library of Congress

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