Sand baths

Most students will be familiar with simple distillation from their practical inorganic chemistry. Other students should determine the boiling-point of acetone (56°), using a water-bath and water-condenser, or of benzene (81 ), using a sand-bath and water-condenser, and finally of either aniline (184 ) or nitrobenzene (210 ), using for both these liquids a sand-bath and air-condenser. 

Assemble the apparatus shown in Fig. 56. F is a 200 ml. flat-bottomed flask supported on a sand-bath and connected by a glass delivery-tube to the wash-bottle B, which is about two-thirds full of 10% aqueous sodium hydroxide solution. A second delivery-tube leads from B into a beehive stand (or between two earthenware tiles placed side by side) in a pneumatic trough T containing water. 

Place 20 ml. (16 g.) of rectified spirit in F, and add slowly, with cooling and shaking, 40 ml. (74 g.) of concentrated sulphuric acid. Then add about 2-3 g. of clean dry sand, to ensure a steady evolution of ethylene subsequently. Connect up the apparatus and heat F over the sand-bath as shown. 

Ethyl bromide soon distils over, and collects as heavy oily drops under the water in the receiving flask, evaporation of the very volatile distillate being thus prevented. If the mixture in the flask A froths badly, moderate the heating of the sand-bath. When no more oily drops of ethyl bromide come over, pour the contents of the receiving flask into a separating-funnel, and carefully run oflF the heavy lower layer of ethyl bromide. Discard the upper aqueous layer, and return the ethyl bromide to the funnel. Add an equal volume of 10% sodium carbonate solution, cork the funnel securely and shake cautiously. Owing to the presence of hydrobromic and sulphurous acids in the crude ethyl bromide, a brisk evolution of carbon dioxide occurs therefore release the... 

Place 20 g. of benzoic acid and 20 ml. (16 g.) of ethanol in A, connect up the apparatus, and then heat the flask on a sand-bath so that the solution in the flask boils gently. At the same time, pass a brisk current of hydrogen chloride into the reaction... 

Boil the mixture gently on a sand-bath for 4 hours and then decant into a conical flask and cool. Seed the cold solution if necessary with a trace of a-methylglucoside. The glucoside separates as colourless crystals. When crystallisation ceases, filter the glucoside at the pump, drain, wash quickly with a small quantity of methanol, and then recrystallise from a minimum of methanol. For this purpose methanol of good quality, but not necessarily anhydrous, should be used. The a-methylglucoside is obtained as colourless crystals, m,p. 165°. Yield, 6-7 g. 

Sand. Buckets of dry sand for fire-extinguishing should be available in the laboratory and should be strictly reserved for this purpose, and not encumbered with sand-baths, waste-paper, etc. Most fires on the bench may be quickly smothered by the ample use of sand. Sand once used for this purpose should always be thrown away afterwards, and not returned to the buckets, as it may contain appreciable quantities of inflammable, non-volatile materials e.g., nitrobenzene), and be dangerous if used a second time. 

A shallow metal vessel containing sand, the so-called sand bath, heated by means of a flame, was formerly employed for heating flasks and other glass apparatus. Owing to the low heat conductivity of sand, the temperature control is poor the use of sand baths is therefore not... 

The simplest form of apparatus consists of a small porcelain evaporating dish covered with a filter paper which has been perforated with a number of small holes a watch glass of the same size, convex side uppermost, is placed on the filter paper. The substance is placed inside the dish, and the latter heated with a minute flame on a wire gauze or sand bath. The sublimate collects in the Fig. II, 45, 1. watch glass, and the filter paper below prevents the sublimate from falling into the residue. The watch glass may be kept cool by covering it with several pieces of damp filter... 

The tube is much longer than needed for the catalyst volume to provide a surface for preheating and to minimize temperature losses at the discharge end. The tube can be bent into a U shape and immersed in a fluidized sand bath, or it can be straight and placed inside a tubular furnace in a temperature-equalizing bronze block. Thermocouples are usually inserted... 

Fit up the apparatus as shown in Fig. 43. The distilling -flask should have a capacity of not less than i litre, and is attached to a long condenser. An adapter is fixed to the end"of the condenser, dipping into a conical flask (250 c.c.), which serves as receiver. The alcohol and sulphuric acid are mixed in the distilling flask and cooled to the ordinary tempeiatuie under the tap. The potassium biomide, coarsely pou dered, is then added. The flask, which is closed with a cork, is fixed to the condenser and heated on the sand-bath. A sufficient quantity of water is poured into the receiver to close the end of the adapter. After a short tune the liquid in the flask begins to boil and froth up, and the ethyl bromide, in the form of heavy... 

A bent tube, which passes thiough one hole, connects the flask with a conclensei and receiver. A tap-funnel is inserted thiough the other hole. The flask is placed upon a sand-bath, and the receiver is cooled in ice. It is important that all the corks should Ire tight, as a small leak will considerably diminish the yield. 1 he potassium bichi ornate in small pieces and the 420 C..C. of water are placed in the flask and gently warmed. 

Sublimation.—A poition of the dry subsiam.c may be purified by sublimation. It is placed (2—3 gtamsj on a l.irge uatch-glass, which is heated on the sand-bath ovei a vcia small flame. The watch-glass is covered with a sheet of filter papei, which is kept flat by a funnel ]daced above. After five minutes or so pale yellow, needle-shaped crystals of anthraquinone will have sublimed on to the filter ptiper. 

The 40 percent, fuming sulpluim acid is removed from tlu-bottle by cautiously melting il in a sand-bath,, iiul it is then weighed out in a flask ( litre). The anthraquinone is aikled. and the flask attached by a coik to an an-condenser. TIh-... 

Heating of 8-hydroxyquinolinium chloride 294 on a sand bath without solvent in the presence of catalytic amount of piperidine for 30 min yielded 2-OXO-2,3-dihydropyrido[ 1,2,3-de]-1,4-benzoxazinium chloride (253)... 

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