Still heads

In simple distillation still heads form the connecting link between the still pot and the condenser. As a rule they have provision for a thermometer. Fig. 238—1 and IS show common types. Those having a ground joint for the thermometer are to be preferred, as they ensure that the thermometer bulb will always be in the same position in the vapour tube, a fact of importance in comparative distillations. 

A number of still heads have been standardized. Table 68 lists the respective specification sheets. Some examples are shown in Fig. 297. 

9977 bridge-type head with ground joint for thermometer 

9979 Claisen still head with lateral ground joint 

9980 still head with fused-on Liebig condenser 

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The reaction is best carried out in the apparatus used in the preparation of quinoline, a 1500 ml. flask being fitted with a wide-bore air-condenser carrying in turn a water-condenser a still-head to fit the flask for subsequent steam-distillation should be assembled in advance. 

Fig. II, 17, 2 illustrates a fractional distillation unit f for use with glass helices. The column is provided with an electrically-heated jacket the resistance shown in the Figure may be replaced by a variable transformer. The still head is of the total-condensation variable take-off type aU the vapour at the top of the column is condensed, a portion of the condensate is returned to the column by means of the special stopcock (permitting of...

Attention is directed to the fact that ether is highly inflammable and also extremely volatile (b.p. 35°), and great care should be taken that there is no naked flame in the vicinity of the liquid (see Section 11,14). Under no circumstances should ether be distilled over a bare flame, but always from a steam bath or an electrically-heated water bath (Fig.//, 5,1), and with a highly efficient double surface condenser. In the author s laboratory a special lead-covered bench is set aside for distillations with ether and other inflammable solvents. The author s ether still consists of an electrically-heated water bath (Fig. 11, 5, 1), fitted with the usual concentric copper rings two 10-inch double surface condensers (Davies type) are suitably supported on stands with heavy iron bases, and a bent adaptor is fitted to the second condenser furthermost from the water bath. The flask containing the ethereal solution is supported on the water bath, a short fractionating column or a simple bent still head is fitted into the neck of the flask, and the stUl head is connected to the condensers by a cork the recovered ether is collected in a vessel of appropriate size. 

If preferred, the following alternative procedure may be adopted. The absolute alcohol is placed in a 1 5 or 2 litre three-necked flask equipped with a double surface reflux condenser and a mercury-sealed mechanical 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 still 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. 

Reduction adapters. These may be employed to connect condensers, still-heads, etc. to flasks, extraction apparatus and the like. Numerous combinations (Fig. II, 56, 2) are, of course, possible, but the commonest sizes are socket 514 to cone 519 or 524 socket 519 to cone 524, 529... 

Distillation heads (or still heads). Fig. II, 56, 5 is a bend ( knee tube ), which is frequently employed for distillation. Convenient sizes are bottom cone 19, 24, 29 or 34 side cone 19 or 24. 

The Stedman-type column is shown in Fig. 11, 56, 25. The characteristic features are (i) the use of a fine stainless steel wire cloth formed into conical discs, and (ii) an accurately fitting Pyrex glass jacket, produced by shrinking Pyrex glass on mandrels to the required inside dimensions. Modifications incorporating a silvered vacuum jacket and an electrically-heated jacket are marketed. This column is said to possess high efficiency but is expensive. It is generally employed in conjunction with a total-condensation variable take-off still head. 

Pour the reaction mixture into a 1-litre round-bottomed flaak, add 250 ml. of water, fit a still head and a condenser for downward distillation (Fig. II, 13, 3, but without the thermometer). Distil the mixture until about 125 ml. of distillate (two layers) have been collected. Saturate with salt (about 30 g. are required), and separate the upper layer of cj/cZohexanone extract the aqueous layer with 25-30 ml. of ether and combine the ether extract with the cycZohexanone layer. Dry with about 6 g. of anhydrous sodium or magnesium sulphate, filter the solution into a distilling flask of suitable size to which a condenser has previously been attached. Distil oflF the ether from a water bath—a beaker containing warm water is satisfactory. Distil the residual liquid from an air bath or a wire gauze, and collect the cyclohexanone at 153-156°. The yield is 16 g. 

In a 500 ml. three-necked flask, equipped with a thermometer, mechanical stirrer and efficient reflux condenser, dissolve 16 g. of sodium hydroxide pellets in 95 ml. of hot methyl alcohol. Add 49 g. of guanidine nitrate, stir the mixture at 50-65° for 15 minutes, and then cool to about 20°. Filter oflF the separated sodium nitrate and wash with two 12 ml. portions of methyl alcohol. Return the combined filtrates to the clean reaction flask, add 69 g. of sulphanilamide (Section IX,9) and stir at 50-55° for 15 minutes. Detach the reflux condenser and, with the aid of a still-head ( knee-tube ), arrange the apparatus for distillation from an oil bath with stirring about 100 ml. of methyl alcohol are recovered. Add 12 g. of pure cycZohexanol. Raise the temperature of the oil bath to 180-190° and continue the distillation. Reaction commences with the evolution of ammonia when the uiternal temperature reaches 145°. Maintain the... 

It is sometimes necessary to remove the products of a reaction in a flask (Fig. XII, 1, 1, a) by distillation. The still head depicted in Fig. XII, 2, 5 may be used for this purpose the side arm may be fitted with a water condenser, if required. 

Aluminum foil (to wrap flask still head-insulation)... 

Set-up for vac-distillation. She wraps the flask and still head with aluminum foil to act as an insulator. Speeds up the distillation process. Begin to heat the DCM extraction slowly under maximum... 

The inlet tube for steam should reach to the bottom of the distillation flask. A i6-mm. bulb on the end of this tube with four 0.8-mm. openings helps to insure thorough mixmg of the heavy residue. If this is not well stirred the aldehyde distils very slowly. It is well to connect the flask to the condenser through a large Hopkins still head in order to prevent the entrainment of foam during the distillation. 

A small amount of dimethylamine is always present in the crude product. This is removed before collection of the product by operating the column under total reflux for 1-2 hours. The vent of the still head should be connected to a hood during this operation. If foaming does not subside after this treatment the use of a 1-1. still pot is indicated. 

A 500-ml, three-necked, round-bottom flask is equipped with a condenser, a dropping funnel, and a thermometer in the reaction mixture. In the flask is placed a mixture of 85% hydrazine (115 ml, 118 g) and 225 ml of 95% ethanol with a few boiling chips. The solution is brought to reflux (mantle) and cinnamaldehyde (100 g, 0.76 mole) is added dropwise over about 30 minutes followed by an additional 30 minutes of refluxing. A still head is attached to the flask and volatiles (ethanol, water, hydrazine hydrate) are slowly distilled at atmospheric pressure until the pot temperature reaches 200° (about 3 hours). Hereafter, phenylcyclopropane is collected over the range 170-180°. When the pot temperature exceeds 250°, the recovery is complete. The crude product (55-65 g) is washed twice with 50-ml portions of water and dried (anhydrous potassium carbonate). Distillation under vacuum through a short column affords the product, bp 60°/13 mm, 79-80°/37 mm, n f 1.5309, about 40 g (45%). 

Destillier-gefkss, n. distilling vessel. gUc, n. distilling vessel (of glass), -liaus, n. still-house, -helm, n. still head, -kolben, m. 

Helm, m. helmet helm (of a still) head. >kolben, m. distilling flask. -rohr, n.,. Schnabel, m. (of a still) beak, nose. 

Sodium ethoxide from sodium (3.67 g) in absolute alcohol (64 ml) was added over 20 minutes with stirring to a mixture of ethyl 4-i-butylphenylacetate (28.14 g) and ethyl carbonate (102 ml) at lOO C. The reaction flask was fitted with a Fenske column through which alcohol and then ethyl carbonate distilled. After 1 hour when the still head reached 124°C heating was discontinued. Glacial acetic acid (12 ml) and water (50 ml) was added to the stirred ice-cooled mixture and the ester isolated in ether, washed with sodium carbonate solution, water and distilled to give ethyl 4-i-butylphenylmalonate. 

The aniline may also be quite satisfactorily removed by distillation under atmospheric pressure, using an efficient fractionating column, the distillation being interrupted when the thermometer in the still head registers 235°. 

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