Heating, Hickman still

Figure 3. Dependence of yield and heat transfer coefficients with operating temperature of Badger-Hickman still...

The objectives of this phase of the program were to determine the maximum heat transfer coefficient that may be expected with a rotating surface and to devise an inexpensive method of packing such surfaces into a vapor compression still. The model available for this study was the No. 4 Badger-Hickman still, shown in diagrammatic elevation in Figure 5, as received and before various modifications were made. 

For ordinary laboratory work, a modified Hickman still (Fig. 1-39) is convenient. Volatile impurities and gases present in the liquid to be distilled must first be removed so that frothing wiU not occur in the still. This is done by placing the liquid in an ordinary flask, which is then evacuated and gently warmed. After all of the volatile impurities have been removed, the liquid is transferred to the still. The latter is connected to the vacuum system by means of a large connector in order to minimize pressure drop in the system. The still is heated by an aluminum block which is bored to accommodate the bottom of the still to a depth of about 15 mm and which is wrapped with nichrome wire serving as a heater. The wire is best insulated from the block by asbestos paper, and a layer of asbestos paper should be placed between the still and the aluminum block. As the liquid is heated, it evaporates and collects on the condenser from which it drips... 

To a 50-mL flask was added 1.32 g anhydrous potassium phenolate (0.01 mol) and 50 g benzaldehyde (0.47 mol). The flask was sealed off and was then heated at 100°C for 18 h. The reaction mixture was filtered, and the filtrate was distilled in a Hickman still to remove residual salts. The distillate was redistilled through a Vigreaux distilling column at 10 mmHg to yield 15 g benzyl benzoate. 

Using the procedure described in Technique 16, Section 16.4, distill the product by vacuum distillation using an apparatus fitted with a Hickman still and a water-cooled condenser (Technique 16, Figure 16.5). Place a small piece of a stainless steel sponge in the lower stem of the Hickman still to prevent bumpover and stir vigorously with a magnetic spin vane. Use an aspirator for the vacuum source and attach a manometer if one is available (Technique 16, Figure 16.10). You may use an aluminum block to heat the dishllation mixture. The aluminum block temperature will be about 130°C (with 20 mm Hg vacuum). If you have less than 0.75 mL, you should combine your product with that of another student. 

ADDED. A Distillation apparATRS using a HickMAN still, A WAter-coOled CondeNseR, and a drying TiBE packed with CaCljWAS ASSEHVBLEP. the SAIRPlE was heated in an aluminum SLOLK At about ltO C. the liquid began boiling after about five miMS,... 

The Hickman Head. Two types of Hickman head (also called a Hickman "still") are shown in Figure 14.4. One of these variations has a convenient opening, or port, in the side, making removal of liquid that has collected in it easier. In operation, the liquid to be distilled is placed in a flask or vial attached to the bottom joint of the Hickman head and heated. If desired, you can attach a condenser to the top joint. Either a magnetic spin vane or a boiling stone is used to prevent bumping. Some typical assemblies are shown in Figures 14.5 and 14.7. The vapors of the heated liquid rise upward and are cooled and condensed on either the walls of the condenser or, if no condenser is used, on the inside walls of the Hickman head itself. As liquid drains downward, it collects in the circular well at the bottom of the still. 

If you are using a sand bath, material may be lost because the hot sand bath radiates too much heat upward and warms the Hickman still. If you believe this to be the case, it can often be remedied by placing a small square of aluminum foil over the top of the sand bath. Make a tear from one edge to the center of the foil to wrap it around the apparatus. 

Figure 3.14 Hickman still head and air condenser with 5-mL round-bottom flask, arranged for microbumer heating.

Hickman Still-Rotary Evaporation Apparatus. A simple microscale rotary evaporator for use in the instructional laboratory consists of a 10-mL round-bottom flask connected to a capped Hickman stOl (side-arm type), which in turn is attached to a water aspirator (with trap) The procedure involves transferring the solution to be concentrated to the preweighed 10-mL flask. The flask is then attached to a Hickman stiH with its top joint sealed with a rubber septum and threaded compression cap. The apparatus is connected by the stiU side arm to the trap-vacuum source with a vacuum hose. lAdth the aspirator on, one shakes the apparatus while warming the flask in the palm of the hand. In this manner, bumping is avoided and evaporation is expedited. The stiU acts as a splash guard. Heat transfer is very effective, and once the flask reaches ambient temperature, the vacuum is released by venting through the trap stopcock. 

Figure 3.15 Hickman-Hinkle still head with side-port 3- or 5-mL conical vial. Teflon spinning band, and thermometer adapter and arranged for heating and magnetic stirring.

Short path and molecular distillation were developed in the 1930s and 1940s mainly in the UK and in the USA. Different types of apparatus were developed. A still with a disk, rotating at high speed, is named after Hickman, one of the pioneers [2]. In this machine the centrifugal force is used to distribute the feedstock as a thin film on a heated disk. Exposure time is less than a few seconds ... 

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