. American journal of pharmacy. flow. For high-boiling liquids ordinary fractionation flasks areused, which are provided with an offset before the gas blast; thespace between the latter and the lateral tube is again filled withbroken glass {Fig. 5), For fractionation in the vacuum, when the Ana. Jour. Pharni. 1December, 1899. J Analysis of Essential Oils. 579 use of a capillary tube is indispensable, to prevent bumpinfr, theform Fig. 6 of flasks is very convenient; the tube / takes up thecapillary. These flasks are an article of commerce. To avoid overheating of the liquid and to secure a very
. American journal of pharmacy. flow. For high-boiling liquids ordinary fractionation flasks areused, which are provided with an offset before the gas blast; thespace between the latter and the lateral tube is again filled withbroken glass {Fig. 5), For fractionation in the vacuum, when the Ana. Jour. Pharni. 1December, 1899. J Analysis of Essential Oils. 579 use of a capillary tube is indispensable, to prevent bumpinfr, theform Fig. 6 of flasks is very convenient; the tube / takes up thecapillary. These flasks are an article of commerce. To avoid overheating of the liquid and to secure a very even dis-tillation, the use of a bath instead of the heating with free flame isrecommended. A bath of any fatty oil, or of liquid paraffine, willgenerally be serviceable; more convenient, however, because of notbeing inflammable and not giving off any offensive vapors at hightemperatures, is a bath from Woods metal, which melts at about60° C.; it is true that the first cost is somewhat high, but it willlast a lifetime. riG. 4. A very common fault of beginners i?, to take Irom the startfractions within very narrow intervals of temperature, in theopinion thus to effect a quicker fractionation. Soon they thenhave such a large number of small fractions that the indications ofthe thermometer become quite uncertain because the rise in dis-tillation temperature of the successive fraction is so fast that anexact reading off is impossible. Such a proceeding also appearsto be quite misleading, if we consider the very imperfect sepa-ration during the first fractionations. It is much better first todivide the whole oil into four or five about equal fractions, without 58o Analysis of Essential Oils. nd^m^^^xm. much regard to their boiling points. The latter may be, forinstance, 170°-:85°, i85°-2io°, 2io°-240°, 240°-28o°. Now westart again with the first fraction. It will begin to boil below 170°,say at 160°; nevertheless we take again a fraction to 185°. Atthis temperature the
Size: 1721px × 1452px
Photo credit: © The Reading Room / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bookcentury1800, bookdecade182, booksubjectpharmacy, bookyear1829
