File:Image from page 83 of "Practical methods of organic chemistry" (1901) (14748627286).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: ff smoothlywithout splintering. If the glass does not crack at once,the heated portion is moistened with a few drops of /water, and the breaking off will follow with certainty. Volhard Tubes. — The tube described by Volhard(Fig. 46) may be used to great advantage when it isdesired to heat large quantities of substances in a singletube. It consists of a wide tube to the end of which anarrower one is fused. A tube of this kind, 35 mm. indiameter and 45 cm. in length, contains about \ of alitre, and possesses the further advantage of being easyto seal. If on opening the tube care be taken, to cutoff as small a portion of the narrow end as possible,it may be used repeatedly. If, finally, the narrowedportion becomes too short, another piece of the samekind of tubing is sealed on. - ig. 4 . Pressure Flasks. Autoclaves. — In order to heat substancesunder pressure at a moderate temperature which on reacting witheach other evolve no gaseous products, so that no pressure due 64 GENERAL PART

Text Appearing After Image: to the reaction is developed, they are sometimes enclosed in strong-walled flasks (pressure flasks), wrapped up in a cloth andheated in a water-bath. Very well adapted to this purpose are the commonsoda-water or beer bottles, of the kind representedin Fig. 47. In using them they are not immersed inwater already heated, but are slowly heated with thewater. The water-bath is closed by a loosely fittingcover, so that in case the bottle bursts, one may notbe burned by the hot water. The flasks are notopened until after they arecompletely cold.1G 47 Large quantities of sub- stances which do not act on metals may be heated under pressure in closed ves-sels, generally made of iron, bronze or copper (autoclaves). Such vessels are not suited for heating acid substances, but may be used for neutral or alkaline substances. In this laboratory Mannes- mann tubes (without seams) are in use, one end being welded together, and the v other is supplied with a screw-thread 1 and cap. The open end is con

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