Heating sand baths

The coke formed in the Vycor reactor had been produced in runs (13) conducted about one year prior to inspection. The detailed history of the reactor is reported in Table III. The inlet half of the reactor was clear, showing no signs of coke deposition. The outlet half was, however, covered with coke to make the reactor black and almost opaque. The exit end of the reactor outside the heated sand bath was covered with a... 

The flask should be gently heated (sand bath or asbestos plate). The HCN condenses in the Liebig condenser and in the round-bottom flask. 

Heating source - Hot plates (electric), electrically or steam-heated sand baths, or a steam bath are recommended for heating perchloric acid. Direct flame heating or oil baths should not be used. 

With this method, a measured or weighed water sample is heated in a suitable evaporation vessel until the water is almost completely evaporated and only those substances which were previously dissolved in the water and are not volatile at the selected temperature remain in the dish. The vessel can be a weighed platinum, glass or porcelain dish, and the sample is heated over a boiling water bath, a heated sand bath, an electric hot plate or an air bath. The evaporation residue can then be dried to constant... 

Heating liquids on an open plate or water bath is very inconvenient in a ship s laboratory. Several methods in Part IV call for prolonged heating at 100 C. An electrically heated sand bath can be used but we recommend an electrically heated metal block with holes drilled for the various containers. Such blocks are easily constructed, or a suitable piece of equipment (with some modification) can be purchased directly from Hallikainen Instruments, Berkeley, California, USA. 

Experience in the Avriter s laboratoly indicat-es that the accuracy of this procedure is improved if the acid hexamethylenetetramine solution is not owed to boil. This may be carried out in a satisfactory manner by piac ingthe beater on a steam-heated sand bath (135 140 C) under a fume hood. The tune required for analysis may be reduced if water is not added to the evaporating solution. With an approximately 0.5 g sample of hexamethylenetetramine, the liberated formaldehyde is completely aporized in appro.rimately 2 to 3 hours. Methyl orange is recommended as a titration indicator. 

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... 

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... 

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... 

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. 

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)... 

By the procedure described in the preceding experiment, 30 g (0.11 mole) of tri-phenylphosphine dissolved in 100 ml of acetonitrile is converted to triphenylphosphine dibromide. After the addition of the bromine has been completed, the cooling bath is removed, the flask is set up for vacuum distillation, and the solvent is removed. To the residue is added /7-chlorophenol (10.3 g, 0.08 mole), and the flask is heated at 200° (mantle, wax bath, or sand bath) until HBr ceases to be evolved (about 2 hours). The flask is cooled and the contents are steam distilled affording crude / -chlorobromo-benzene in about 90% yield. Recrystallization from benzene gives the pure product, mp 65-66°. 

Neutral alumina (12 g) is placed in a 250-ml flask and partially deactivated by the addition of 0.12 g (2-3 drops) of water. The alumina is allowed to stand with occasional swirling for 30 minutes. To the flask is added 20 g of 1,4-cyclohexanediol (Chapter 5, Section II). A short Vigreux column is placed over the flask, which is then arranged for distillation. The mixture is heated at 240° with a sand bath or mantle, whereupon distillation commences (caution, bumping). The distillation is continued until the alumina is dry (5-8 hours). The distillate, which consists of two layers, is added to 75 ml... 

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