Fractionating columns Hempel

Fig. II, 16, 1 illustrates a set-up for simple fractionation a Hempel column is shown, but it may be substituted by a modified Hempel, a Vigreux or an all-glass Dufiton column. The Hempel column may be filled with glass rings, h porcelain Lessing rings, or with porcelain rings. The mixture to be fractionated is placed in a bolt - head flask of convenient size (it should be one third to one half full), a few fragments of porous porcelain added, the column fixed in position, and a water condenserattacfied to the side arm. The distillate is collected in small flasks or in test tubes. The bulb of the thermometer should be just below the level of the side arm.

The 40-45 per cent, hydrazine solution may be concentrated as follows. A mixture of 150 g. (144 ml.) of the solution and 230 ml. of xylene is distilled from a 500 ml. round-bottomed flask through a well-lagged Hempel (or other efficient fractionating) column fitted into a cork covered with tin foil. All the xylene passes over with about 85 ml. of water. Upon distillation of the residue, about 50 g. of 90-95 per cent, hydrazine hydrate (5) are obtained. 

The best results are obtained b distillation from a small flask through a short fractionating column a Hempel column tilled with glass rings (Fig. 11,16, 1) and lagged with asbestos cloth or several thicknesses of linen cloth is quite satisfactory. 

Alternatively, an independent column (Fig. XII, 2, 8, c) may be inserted into a flask the column may be of the Vigreux, Widmer or Hempel form. The fractionating column should be lagged with asbestos cloth or string for distillation temperatures above 100° for the best results the column should be heated electrically (compare Section 11,15) to a temperature 5-10° below the b.p. of the fraction being collected. The side arm of the flask or fractionating column may be attached to a cold spot condenser and receiver as in Fig. XII, 2, 4 or to a Liebig s condenser and receiver as in Fig. XII, 2, 1. 

Hempel fractionating column, 137 Hofmann s bottles 30 Hot-water funnel, 53 Hydrazobenzene, 146 Hydriodic acid, 113 Hydrobenzamide, 196 Hydrobromic acid, 140 Hydrochloric add gas, 93 Hydrocinnamic acid, 204 Hydrogen, qualitative determination, r quantitative, ... 

Fig. II, 16, 1 illustrates a set-up for simple fractionation a Hempel column is shown, but it may be substituted by a modified Hempel, a Vigreux or an all-glass -Dufton column. The Hempel column may be filled with glass rings,...

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