File:Image from page 38 of "Practical methods of organic chemistry" (1901) (14748613896).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: -ticularly well adapted ; in working withit as well as the Linnemann form, theheating must be interrupted from timeto time, in order that the liquid col-lecting in the beads or sieves may have an opportunity to flowback to the distillation flask. If the Le Bel-Henninger form isused, this precaution is unnecessary, since in this apparatusspecial tubes for conducting off the condensed liquid are joinedto the sides of the bulb somewhat above the sieves. Experiments have shown that a single distillation with one of theforms of apparatus just described, effects a more complete separa-tion than repeated fractionations in an ordinary fractionating flask. Supporting the Fractionating Flask. — If it is necessary tosupport the fractionating flask with a clamp, it is placed as farabove the outlet tube as possible, never below it; the glass ex-pands by contact with the hot vapours, and since the expansionis impeded by the clamp, particularly if it is firmly attached, theflask frequently breaks.

Text Appearing After Image: Fig. 16. 20 GENERAL PART Supporting the Thermometer. — The thermometer is passedthrough a cork (no rubber) which fits the neck of the flask. Themost exact determinations of the boiling-point are obtained if theentire thread of mercury is surrounded by the vapour of the sub-stance. With low boiling compounds this condition is easilyobtained by the use of a fractionating flask having its outlet tubeat a sufficient distance above the bulb. In this case the ther-mometer is so placed that the degree corresponding to the boil-ing-point of the liquid is opposite the outlet tube, but the bulbof the thermometer must not extend into the bulb of the flaskand never into the liquid ; if it does, another flask must be used,the outlet tube of which is still higher above the bulb. If indealing with high boiling compounds such an arrangement isnot possible, the thermometer is thrust so far into the neck of theflask that the thermometer-bulb is somewhat below the outlettube. In this case, if an exact

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