StiU-head

If preferred, the following alternative procedime may be adopted. The absolute alcohol is placed in a 1 5 or 2 htre three-necked flask equipped with a double surface reflux condenser and a mercury-sealed miechanical stirrqr the third neck is closed with a dry stopper. The sodium is introduced and, when it has reacted completely, the ester is added and the mixture is gently refluxed for 2 hours. The reflux condenser is then rapidly disconnected and arranged for downward distillation with the aid of a short stiU head or knee tube. The other experimental details are as above except that the mixture is stirred during the distillation bumping is thus reduced to a minimum. 

Using the system dichloroethane-toluene as an ejcample Wagner and Blass [262] describe a procedure for a hybrid analog computer which simulates stepwise rectification. This allows the determination of the stiU head or still pot concentration in the separation of binary mixtures for given operating parameters and equilibrium curves as a function of time. 

Simple unrectified distillation is used in the laboratory chiefly for the recovery of solvents and other contaminated liquids, and for performing initial separations on large amounts of mixtures. The only apparatus needed for this purpose is a flask, a stiU head with a ground-in thermometer and components for condensation, vacuum connection and collecting the distillate. It is frequently advisable to include a spray trap consisting of a short section — say 5 to 10 cm — of column. Fig. 238 demonstrates the wide range of possibilities offered by the use of readily available parts [9]. 

Microscale spinning-band distillation apparatus (Fig. 5.11) can achieve nearly 12 theoretical plates and are simple enough to be used in the instructional laboratory. This stiU has a Teflon band that fits closely inside an insulated glass tube. The Teflon band has spiral grooves which, when the band is spun (1000-1500 rpm), rapidly return condensed vapor to the distillation pot. A powerful extension of this apparatus uses a short spinning band inside a modified Hickman stiU head (see Fig. 3.15). These stills are called Hickman-Hinkle stills 4-cm Hickman-Hinkle columns can have more than 10 theoretical plates. The commercially available 2.5-cm version is rated at 6 theoretical plates. Experiments [3C] and [3D] involve fractional distillation with spinning-band columns. 

Concentration of solvent by distillation is straightforward, and the standard routine is described in Technique 2 (page 61). This approach allows for high recovery of volatile solvents and often can be done outside a hood. The Hickman stiU head and the 5- or 10-mL round-bottom flask are useful for this purpose. Distillation should be used primarily for concentration of the chromatographic fraction, followed by fransfer of the concentrate with a Pasteur filter pipet to a vial for final isolation. 

With stiU-head at f. From mixture boiling atr. 

Nature of still-bead. 3 bulbs. 7 bulbs. 13 bulbs. Pear" stiU-head, 13 bidbs. 

The dried malted barley is ground and mashed in a tub, after which the Hquid portion is drained off, cooled, and placed in the fermentor. After fermentation, a batch distillation system is usually used to separate the whisky from the fermented wort. The stiU consists of a copper ketde with a spiral tube or "worm" leading from the top. The dimensions and shape of the stills have a critical effect on the character of the whisky. The product taken off in the first part of the distillation is called foreshots (heads). The middle portion is the high wines and the last portion is the feints (tails). The middle portion is redistilled at the 140—160° proof (70—80%) range and matured in used oak cooperage. 

Naturally, the quality of these decomposition approaches is considerably affected by the neglected interdependency of the decomposed decisions. Therefore, monolithic, time and volume-continuous MILP formulations are proposed recently to integrate these decisions. These models are straight-forward adaptations of one-to-many approaches. The basic setting is adapted from the one-to-many case (see the previous paragraph), i.e. a serially operated main pipeline is assumed with a refinery at its head and depots along this pipeline. One key alteration is that depots now can receive and inject batches in the pipeline. Most other assumptions are inherited from the one-to-many systems. In particular, the product flow is stiU unidirectional and only one location at a time can inject a batch in the pipeline. ... 

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