Bath oil

Place a mixture of 5 g. of camphor, 6 g. of powdered selenium dioxide and 5 ml. of acetic anhydride in flask fitted with a reflux water-condenser. Heat the flask in an oil-bath for 3 hours at 140-150 so that gentle boiling occurs shake the mixture from time to time. 

Place in the flask 2 g. of benzophenone, 15 ml. of isopropanol and 2 5 g. of aluminium isopropoxide. This mixture has now to be heated gently under reflux so that the temperature registered by the thermometer in the column does not exceed 80°, i.e., so that only acetone distils. For this purpose, the flask should preferably be heated in an oil-bath direct heating, even over an asbestos sheet, may cause local overheating and decomposition the use of a water-bath on the other hand may make the column undesirably damp. 

Disconnect the column, and remove the flask from the oil-bath. Add 25 ml. of dilute hydrochloric acid to the flask, shake the contents vigorously, and chill in ice-water, when crystals of benzhydrol will separate. (Occasionally the hydrol will separate initially as an oil, which ciystallises on vigorous stirring.)... 

Pour the mixture into a 500 ml. flask fitted with a steam-distillation head, and with a steam-inlet tube reaching almost to the bottom of the flask. First distil off the benzene in steam. Then place the flask in an oil-bath heated to 165-170 ", and continue the steam-distillation (2-3 hours). The /)-bromobiphenyl passes over and forms orange crystals in the water-condenser therefore run the water out of the condenser for a short while from time to time to melt the orange deposit and allow it to run into the receiver containing the distilled water. 

Prepare a mixture of the above compounds in the stated quantities in a flask fitted with a reflux water-condenser. Shake the mixture thoroughly, and then heat it in an oil-bath at 145-150° for 3 hours. After about 10 minutes heating, the mixture gives a clear red solution which should be shaken occasionally during the subsequent heating. 

Assemble in a fume-cupboard the apparatus shown in Fig. 67(A). Place 15 g. of 3,5-dinitrobenzoic acid and 17 g. of phosphorus pentachloride in the flask C, and heat the mixture in an oil-bath for hours. Then reverse the condenser as shown in Fig. 67(B), but replace the calcium chloride tube by a tube leading to a water-pump, the neck of the reaction-flask C being closed with a rubber stopper. Now distil off the phosphorus oxychloride under reduced pressure by heating the flask C in an oil-bath initially at 25-30, increasing this temperature ultimately to 110°. Then cool the flask, when the crude 3,5-dinitro-benzoyl chloride will solidify to a brown crystalline mass. Yield, 16 g., i.e,y almost theoretical. Recrystallise from caibon tetrachloride. The chloride is obtained as colourless crystals, m.p. 66-68°, Yield, 13 g Further recrystallisation of small quantities can be performed using petrol (b.p. 40-60°). The chloride is stable almost indefinitely if kept in a calcium chloride desiccator. 

Mix 1 g. of quinaldine and 1 g. of powdered />-dimethylaminobenzab dehyde, add 2 -3 drops of 10% etl nolic zinc chloride solution, and heat under reflux in an oil-bath at 150 for 1 hour. Cool the product in ice-water, and reciystallise it from ethanol. p-Dimethylaminostyryl-quinoline (I) separates as bright yellow crystals, m.p. 177-178°. 

B) Sulphonamides. Mix 0 5 g. of the sulphonic acid or its alkali salt with 15 g. of phosphorus pentachloride, and heat under reflux in a silicone- or oil-bath at 150° for 30 minutes then allow it to cool. 

It must be borne in mind that in spite of the fact that the solvents have normal boiling points below 90-95°, they cannot always be completely removed by heating on a steam or water bath when they form part of mixtures with less-volatile liquids. Simple distillation may lead to mixtures with higher boiling points than the individual solvents, so that separation of the latter may not be quite complete. In such cases the distillation should be completed with the aid of an air bath (Fig. 77,5,3) or an oil bath the Are hazard is considerably reduced since most of the solvent will have been removed. 

Solvents with boiling points above 90-95°. The apparatus of Fig. 77,13, 3 (with closed filter flask and rubber lead-off tube) or of Fig. 77,13, 4 (see discussion in previous paragraph but one) should be vtilised vrith an air bath or oil bath as the source of heat. Heating on a Wire gauze is not recommended. 

Anhydrous stannous chloride. Crystalline stannous chloride, SnCl2.2HjO, is heated for one hour in an oil bath at 195-200°, the cooled melt is powdered, and kept in a desiccator or in a tightly stoppered bottle. 

For successful fractional distillation, slow and even heating of the bath surrounding the flask is essential. This may be achieved by suitably designed electrically-heated air baths or by the use of oil baths provided... 

Sulphuric acid method. Place 20 g. of commercial cycZohexanol and 0-6 ml. of concentrated sulphuric acid in a 150 or 200 ml. round-bottomed or bolt head flask, add 2-3 chips of porous porcelain, and mix well. Fit the flask with a fractionating column, a Liebig condenser, adapter and filter flask receiver as in Section 111,10 (1). Heat the flask in an air bath (Fig. II, 5, 3) at such a rate that the temperature at the top of the column does not rise above 90° alternatively, an oil bath, heated to a temperature of 130-140°, may be used. Stop the distillation when only a small residue remains and the odour of sulphur dioxide is apparent. Transfer the distillate to a small separatory funnel. 

Alternatively, the following procedure for isolating the glycol may be used. Dilute the partly cooled mixture with 250 ml. of water, transfer to a distilling flask, and distil from an oil bath until the temperature reaches 95°. Transfer the hot residue to an apparatus for continuous extraction with ether (e.g.. Fig. II, 44, 2). The extraction is a slow process (36-48 hours) as the glycol is not very soluble in ether. (Benzene may also be employed as the extraction solvent.) Distil off the ether and, after removal of the water and alcohol, distil the glycol under reduced pressure from a Claisen flask. 

In a 200 ml. distilling flask place 64 g. (50 ml.) of dry n-butyl bromide and 80 g. of dry silver nitrite (1). Insert a reflux condenser, carrying a cotton wool (or calcium chloride) guard tube, into the mouth of the flask and close the side arm with a small stopper. Allow the mixture to stand for 2 hours heat on a steam bath for 4 hours (some brown fumes are evolved), followed by 8 hours in an oil bath at 110°. Distil the mixture and collect the fraction of b.p. 149-151° as pure 1-nitro-n-butane (18 g.). A further small quantity may be obtained by distilling the fractions of low boihng point from a Widmer flask. 

Place 1 0 g. of the monobasic acid and 2 g. of aniline or p-toluidine in a dry test-tube, attach a short air condenser and heat the mixture in an oil bath at 140-160° for 2 hours do not reflux too vigorously an acid that boils below this temperature range and only allow steam to escape from the top of the condenser. For a sodium salt, use the proportions of 1 g. of salt to 1 5 g. of the base. If the acid is dibasic, employ double the quantity of amine and a reaction temperature of 180-200° incidentally, the procedure is recommended for dibasic acids since the latter frequently give anhydrides with thionyl chloride. Powder the cold reaction mixture, triturate it with 20-30 ml. of 10 per cent, hydrochloric acid, and recrystallise from dilute alcohol. 

Place 146 g. of adipic acid, 360 ml, (285 g.) of absolute ethyl alcohol 180 ml. of toluene and 1 - 5 g. of concentrated sulphuric acid in a 1-litre round-bottomed flask, attach a short fractionating column connected to a downward condenser, and heat in an oil bath at 115°, When the acid... 

Dissolve 2 drops of concentrated sulphuric acid in 2 ml. of the ester and add 1 - 5 g. of 3 5-dinitrobenzoic acid. If the b.p. of the ester is below 150°, refiux the mixture gently if the b.p. is above 150° heat the mixture, with frequent shaking at first, in an oil bath at about 150°. If the 3 5-dinitrobenzoic acid dissolves within 15 minutes, heat the mixture for 30 minutes, otherwise 60 minutes heating is required. Allow the reaction mixture to cool, dissolve it in 25 ml. of ether, and extract thoroughly with 5 per cent, sodium carbonate solution (ca. 25 ml.). Wash the ethereal solution with water, and remove the ether. Dissolve the residue (which is usually an oil) in 5 ml. of hot alcohol, add hot water cautiously until the 3 5-dinitrobenzoate commences to separate, cool and stir. Recrystallise the derivative from dilute alcohol the yield is... 

Mix 100 g. of ammonium chloride and 266 g. of paraformaldehyde in a 1-litre rovmd-bottomed flask fitted with a long reflux condenser containing a wide inner tube (ca. 2 cm. diameter) the last-named is to avoid clogging the condenser by paraformaldehyde which may sublime. Immerse the flask in an oil bath and gradually raise the temperature. The mixture at the bottom of the flask liquefies between 85° and 105° and a vigorous evolution of carbon dioxide commences at once remove the burner beneath the oil bath and if the reaction becomes too violent remove... 

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