Water-condensers semi-micro

A short-path distillation procedure may be used in situations where a simple distillation is required, as purification from non-volatile components/fractional distillation with a Kugelrohr apparatus is difficult. A water-jacketed, semi-micro distillation apparatus is illustrated in Figure 1.7. Heating can either be achieved with the aid of an oil-bath, an isomantle, or a flame (Caution ensure that there are no flammable solvents nearby). For larger scale distillations, a round-bottomed flask should be attached to a distillation column, a still-head, and condenser. The column used in the distillation is variable, and may be either a Vigreux column or a column packed with glass helices. 

A very suitable apparatus for semi-micro steam-distillation, particularly for suspensions that are likely to bump badly, is showm in Fig. 44. This consists of a 50 ml. Kjeldahl flask, clamped at an angle of 45°, and fitted with a long glass tube for the inlet of steam. The Outlet-tube is bent twice, first at 135° and then at 45° as shown, and fitted into a small water-condenser. 

Alternatively the semi micro apparatus shown in Fig. 38 (p. 63) may be used. Heat the anilide and sulphuric acid under reflux for 15 minutes in such a manner that the vapour does not rise higher than half-way up the vertical condenser through which water is passed. Then dilute the solution in the flask with 5 ml. of water. Empty the vertical condenser and run cold water through the inclined condenser. Now increase the rate of heating and distil off 1-2 ml. of aqueous acetic acid. 

Dissolve 1 g. of anthracene in 10 ml. of glacial acetic acid and place in 50 ml. bolt head flask fitted with a reflux water-condenser. Dissolve 2 g. of chromium trioxide in 2 ml. of water and add 5 ml. of glacial acetic acid. Pour this solution down the condenser, shake the contents of the flask and boil gently for 10 minutes. Cool and pour the contents of the flask into about 20 ml. of cold water. Filter off the crude anthraquinone at the pump, wash with water, drain well and dry. Yield, 1 g. Purify by re crystallisation from glacial acetic acid or by sublimation using the semi-micro sublimation apparatus (Fig. 35, p. 62, or Fig. 50, p. 70). 

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