Dufton column

The spiral should preferably be ground into the inner walls of the long neck—compare the all.glaas Dufton column. Section 11.15. 

Alternatively, a modified Hempel column (Fig. 77,15, 5) or an all glass Dufton column with 30 cm. spiral (Fig. 77,15, 2) may be used for the fractionation. The latter has the advantage that it is more easily cleaned. 

Any other efficient fractionating column may be used, e.g., an all-glaas Dufton column—see Sections 11,15 and 11,17. 

Any fractionating column of moderate efficiency is satisfactory, e.g., a Dufton column (20 cm. long containing a spiral 10 cm. in length, 2 cm. in diameter with 8 turns of the helix) or a Vigreux column (20-25 cm. long). 

Neutralise the cold contents of the flask with 500-600 ml. of 40 per cent, aqueous sodium hydroxide solution, equip the flask for steam distillation and steam distil until about 1 litre of distillate is collected. The steam distillate separates into two layers. Add solid sodium hydroxide (< 100 g.) to complete the separation of the two layers as far as possible. Remove the upper (organic) layer and extract the aqueous layer with three 50 ml. portions of chloroform. Dry the combined organic layer and chloroform extracts with anhydrous potassium carbonate and distil the mixture through a short fractionating column (e.g., an 8 Dufton column) after a fore run of chloroform, followed by pyridine, collect the crude 4-ethylpyridine at 150-166° (49 g.). Redistil through a Fenske-... 

Any fractionating column of moderate efficiency is satisfactory. The submitters employed a 20-cm. Dufton column... 

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, iV 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 condenser attached 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.

A Dufton column was not available to the checkers. In its place a 2.5-cm. x 38-cm. column packed with glass helices was used. This column was heated by a 4.5-cm. concentric glass jacket wrapped with Nichrome ribbon. A 6.5-cm. concentric... 

Dufton column. A plain tube, into which fits closely (preferably ground to fit) a solid glass spiral wound round a central rod. It tends to choke at temperatures above 100 unless it is lagged (Dufton J Soc Chem Ind (London) 38 45T 1919). 

Widmer column. A Dufton column, modified by enclosing within two concentric tubes the portion containing the glass spiral. Vapour passes up the outer tube and down the inner tube before entering the centre portion. In this way flooding of the column, especially at high temperatures, is greatly reduced (Widmer HCA 7 59 1924). 

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