File:Image from page 36 of "Practical methods of organic chemistry" (1901) (14584971689).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: flask is selected having a bulb of such a size that when it contains thesubstance to be distilled it will be about two-thirds filled. Thereare two objections to distilling small quantities of a substance froma large flask: the vapours are easily overheated, thus giving aboiling-point that is too high; a loss of the substance follows, inthat, after the distillation is finished, a larger volume of vapourswhich condense on cooling, remains behind in the bulb, than if asmaller flask had been used. In the distillation of low boiling DISTILLATION 17 compounds, a flask is selected which has its condensation-tube ashigh as possible above the bulb, so that the entire thread of mer-cury of the thermometer employed is heated by the vapour of theliquid. By using a flask of this kind it is not necessary to cor-rect the observed boiling-point, as is the case when the mercurycolumn is not entirely surrounded by the vapour. The higher asubstance boils, the nearer must the side-tube be to the bulb, in

Text Appearing After Image: Fig. 11. Fig. 13. order that the vapours shall have as little opportunity as possibleof condensing below the tube and flowing back into the bulb. If large quantities of a substance are to be distilled, an ordi-nary flask is used. This can be converted into a fractionatingflask with the aid of a cork bearing a T-tube, as illustrated inFig. 14. For the distillation of solid substances which solidify in thecondensation-tube, a fractionating flask with a wide side-tube isused. A fractional distillation can also be conducted in the fractionatingflasks just described ; but the operation can be carried out morec 18 GENERAL PART rapidly and more completely by the use of apparatus especiallyadapted to fractionating (Fig. 15). These can be fused directlyon the bulb or they can be attached to an ordinary flask by meansof a cork (Fig. 14) ; the round, short-necked flasks such as rep-resented in Fig. 16, are well adapted to this purpose. Flasks of

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