Condensers double-surface

Now filter the ether through a fluted filter-paper directly into a 100 ml. distilling-flask, and then equip the latter with a 100° thermometer and a double-surface condenser to the end of the latter attach a receiver with a rubber delivery-tube precisely as before. Place the flask cautiously in a water-bath, the contents of which have previously been heated to about 60° at some distance from the apparatus arrange the depth of the flask in the water-bath so that the ether distils slowly over. Collect the fraction boiling between 34-39°. Yield, 25 g. (35 ml.). Not more than a verv small residue of etlianol should remain in the flask. 

To prepare pure acetylene, assemble the apparatus shown in Fig. 57. F is a wide-necked 300 ml. bolt-head flask, to which is fitted a double-surface reflux water-condenser C and the dropping-funnel D. From the top of C, a delivery-tube leads down to the pneumatic trough T, where the gas can be collected in jars in the usual way. (Alternatively, use the apparatus shown in Fig. 23(A),... 

The reaction is carried out in a 2-litre long-necked round-bottomed flask, to which is fitted an efficient reflux water-condenser, capable of condensing a sudden rush of vapour without choking. For this purpose, a long bulb-condenser, similar to that shown in Fig. 3(A) (p. 9) is best, but the inner tube must be of wide bore (at least 12 mm.). Alternatively, an air-condenser of wide bore may be used, an.d a short double-surface water-condenser fitted to its top. A steam-distillation fitting for the flask should also be prepared in advance, so that the crude product can subsequently be steam-distilled directly from the flask. The glj cerol used in the preparation must be anhydrous, and should therefore be dehydrated by the method described on p. 113. 

Figs. II, 13, 7 and II, 13, 8 depict various set-ups which involve tlio refluxing of a liquid the Liebig condenser may, of course, be replaced by a double-surface condenser. In Fig. II, 13, 7 a calcium chloride guard protects the contents of the flask from ingress of moisture. The... 

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. 

Mg. 11, 56, 17 (Davies types) and Fig. 11, 56, 18 (double coil type) are examples of efficient double surface condensers. Fig. 11, 56, 19 depicts a screw type of condenser (Friedrich pattern) the jacket is usually 10, 15 or 25 cm. long and the cone and sockets are fil9 or 24 this highly efficient condenser is employed for both reflux and for downward distillation. 

Simple distillation. The assembly shown in Fig. II, 60, 1 is of general utihty for very volatile liquids the Liebig s condenser may be replaced by a double surface condenser. 

Fit the central neck of a 1-litre three-necked flask with an efficient double surface condenser and close the two side necks with corks (1). Place 52 g. (59-5 ml.) of ethyl n-valerate (Section 111,104) and 800 ml. of super-diy ethyl alcohol (Section 11,47, 5) (2) in the flask. Add 95 g. of clean sodium in small pieces through one of the apertures at such... 

Place a mixture of 114 g. (140 ml.) of methyl -amyl ketone (2-hepta-none) (1), 300 ml. of rectified spirit (95 per cent, ethyl alcohol) and 100 ml. of water (2) in a 1500 ml. three-necked fiask or in a 1500 ml. round-bottomed fiask provided with a two-way addition tube (Fig. 11,13, 9). Attach an efficient double surface condenser to the fiask and close the... 

Fit a 500 ml. round-bottomed flask with a dropping funnel and a double surface condenser alternatively, the flask may be provided with a two-way addition tube (Fig. II, 13, 9) and the dropping funnel and condenser inserted into the latter. Place 37 g. (46 ml.) of iso-butyl alcohol (b.p. 106-108°) and 40 g. (41 ml.) of pure pyridine in the flask and 119 g. (73 ml.) of redistilled thionyl chloride in the dropping funnel. Insert a cotton wool or calcium chloride guard tube into the mouth of the funnel. Introduce the thionyl chloride during 3-4 hours a white solid... 

Mix 40 g. (51 ml.) of isopropyl alcohol with 460 g. (310 ml.) of constant boiling point hydrobromic acid in a 500 ml. distilling flask, attach a double surface (or long Liebig) condenser and distil slowly (1-2 drops per second) until about half of the liquid has passed over. Separate the lower alkyl bromide layer (70 g.), and redistil the aqueous layer when a further 7 g. of the crude bromide will be obtained (1). Shake the crude bromide in a separatory funnel successively with an equal volume of concentrated hydrochloric acid (2), water, 5 per cent, sodium bicarbonate solution, and water, and dry with anhydrous calcium chloride. Distil from a 100 ml. flask the isopropyl bromide passes over constantly at 59°. The yield is 66 g. 

Allyl Bromide. Introduce into a 1-litre three-necked flask 250 g. (169 ml.) of 48 per cent, hydrobromic acid and then 75 g. (40-5 ml.) of concentrated sulphuric acid in portions, with shaking Anally add 58 g. (68 ml.) of pure allyl alcohol (Section 111,140). Fit the flask with a separatory funnel, a mechanical stirrer and an efficient condenser (preferably of the double surface type) set for downward distillation connect the flask to the condenser by a wide (6-8 mm.) bent tube. Place 75 g. (40 5 ml.) of concentrated sulphuric acid in the separatory funnel, set the stirrer in motion, and allow the acid to flow slowly into the warm solution. The allyl bromide will distil over (< 30 minutes). Wash the distillate with 5 per cent, sodium carbonate solution, followed by water, dry over anhydrous calcium chloride, and distil from a Claisen flask with a fractionating side arm or through a short column. The yield of allyl bromide, b.p. 69-72°, is 112 g. There is a small high-boiling fraction containing propylene dibromide. 

Owing to the corrosive action of bromine upon corks j-jg 7, l. and rubber stoppers, ground glass joints are recommended in this preparation. The apparatus, depicted in Fig. Ill, 37, 1, is particularly convenient for the preparation of bromides from alcohols. A double surface condenser is fitted into D and a round-bottomed flask is fitted on to the ground glass joint at C R is a three-way stopcock f which permits the removal of the contents of A without disconnecting the apparatus. For preparations of moderate size, A has a capacity of 60 or 100 ml. and a 250 or 500 ml. flask is attached at C. 

Place 92 5 g. (114 5 ml.) of n-butyl alcohol and 8 55 g. of purified red phosphorus (Section 11,50,5) in a 500 ml. round-bottomed flask (attached at C) and 100 g. (32 ml.) of bromine in A. Pass a stream of cold water through the condenser F and through the double surface condenser fitted at D the condenser F prevents the volatilisation of the alcohol from the... 

Alternatively, place the mixture of alcohol and red phosphorus in a 500 ml. three-necked flask fitted with a mechanical stirrer, dropping funnel and double surface condenser. Heat the phosphorus - alcohol mixture to about 250°, and add the bromine whilst stirring vigorously. Work up the reaction product as above. 

In a 1-litre three-necked flask, mounted on a steam bath and provided respectively with a separatory funnel, mechanical stirrer and double surface condenser, place 165 g. of bromoform (96 per cent.). Add 10 ml. of a solution of sodium arsenite made by dissolving 77 g. of A.R. arsenious oxide and 148 g. of A.R. sodium hydroxide in 475 ml. of water. Warm the mixture gently to start the reaction, and introduce the remainder of the sodium arsenite solution during 30-45 minutes at such a rate that the mixture refluxes gently. Subsequently heat the flask on the steam bath for 3-4 hours. Steam distil the reaction mixture (Fig. 11, 41, 1) and separate the lower layer of methylene bromide (79 g.). Extract the aqueous layer with about 100 ml. of ether a further 3 g. of methylene bromide is obtained. Dry with 3-4 g. of anhydrous calcium chloride, and distil from a Claisen flask with fractionating side arm. The methylene bromide boils constantly at 96-97° and is almost colourless. 

The complete assembly for carrying out the catalytic decomposition of acids into ketones is shown in Fig. Ill, 72, 1. The main part of the apparatus consists of a device for dropping the acid at constant rate into a combustion tube containing the catalyst (manganous oxide deposited upon pumice) and heated electrically to about 350° the reaction products are condensed by a double surface condenser and coUected in a flask (which may be cooled in ice, if necessary) a glass bubbler at the end of the apparatus indicates the rate of decomposition (evolution of carbon dioxide). The furnace may be a commercial cylindrical furnace, about 70 cm. in length, but it is excellent practice, and certainly very much cheaper, to construct it from simple materials. 

---