Distillation semi-micro

Distillation Technique. With all distillations on a semi-micro scale it is essential to heat the liquid so slowly that a cushion of its... 

Fractional Distillation. Fractional distillation on a semi-micro scale can be carried out satisfactorily with the fractionating column shown in Fig. 39. The column is 10 cm. long and is filled with pieces... 

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. 

For heating baths, see Table 4. For distillation apparatus on a micro or semi-micro scale see Aldrich and other glassware catalogues. Alternatively, some useful websites for suppliers of laboratory glassware are www.wheatonsci.com,www.sigmaaldrich.com and www.kimble-kontes.com. 

The yield of radioactive D.F.P. from 32P is necessarily small on the semi-micro scale (p. 75) it is better therefore to titrate the fluoride (obtained after the decomposition of D.F.P.) with thorium nitrate, sodium alizarin sulphonate being used as indicator.2 It is necessary, however, first of all, to remove the fluoride by distillation (p. 211). This method gives an accuracy of +1 per cent with 50 mg. of D.F.P. This degree of accuracy on a semi-micro scale3 may be considered fairly satisfactory. 

The ammonium extracted by the potassium chloride reagent is analysed by steam distillation. This may be carried out using an automatic instrument such as the Kjeltec Auto 1035 Analyzer (USDA, 1996, pp. 203-210), or a micro (or semi-micro) steam distillation unit such as that described by Bremner and Keeney (1965), or the readily available Markham still. We will describe the manual procedure. 

Distillation unit - the Markham semi-micro distillation unit is suitable. Reagents. 

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. 

So, since nobody actually has any microscale reduced-pressure distillations, and with certain sizes of equipment the O-rings can squeeze out from under the plastic caps, and since I don t use them for reduced-pressure (vacuum) distillation anyway (I switch to a semi-micro apparatus with real 14/20 joints and—gasp —grease), I don t know how vacuum tight these seals really are. 

Release of Cellulolytic Enzymes. Culture medium was filtered from 4-day-old cultures of D. zeae. The mycelial mats were rinsed with distilled water, then stripped from the filter paper and fragmented in a minimum of distilled water in a semi-micro Waring Blendor cup. Portions of the mycelial suspension were pipeted into solutions of the compounds being tested, and the flasks were shaken in the dark for 20 minutes. The suspensions were then filtered, and the filtrates were assayed for enzyme activity. 

For micro- and semi-micro-distillation smaller flasks are frequently necessary. As a rule these are made with pointed bases, in order that distillation may be continued down to a small residue (Fig. 127). 

The simple Hickman still is used with an O-ring compression cap to carry out semi-micro simple or crude fractional distillations. The Hickman-Hinkle spinning band still uses a 3-cm fractionating column and routinely develops between five and six theoretical plates. The Hickman-Hinkle still is currently available with 14/10 I joints and can be conveniently operated with the 14/10 I 3- and 5-mL conical vials (see Figs. 3.1, 3.3, and 3.7). The still head is also available with an optional sidearm collection port. 

Water-jacketed semi-micro short-path distillation apparatus... 

The following natural precursors have been selected for KOH activation coal (C), coal semi-coke (CS), pitch semi-coke (PS) and pitch mesophase (PM). An industrial activated carbon (AC) was also used. Activation was performed at 800°C in KOH with 4 1 (C KOH) weight ratio, for 5 hours, followed by a careful washing of the samples with 10% HC1 and distilled water. The activation process supplied highly microporous carbons with BET specific surface areas from 1900 to 3150 m2/g. The BET surface area together with the micro and the total pore volume of the KOH-activated carbons are presented in Table 1. The mean micropore width calculated from the Dubinin equation is designed as LD. 

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