Heating baths fusible metal

Place 50 g. of o-chloronitrobenzene and 75 g. of clean dry sand in a 250 ml. flask equipped with a mechanical stirrer. Heat the mixture in an oil or fusible metal bath to 215-225° and add, during 40 minutes, 50 g. of copper bronze or, better, of activated copper bronze (Section 11,50, 4) (1), Maintain the temperature at 215-225° for a further 90 minutes and stir continuously. Pour the hot mixture into a Pyrex beaker containing 125 g. of sand and stir until small lumps are formed if the reaction mixture is allowed to cool in the flask, it will set to a hard mass, which can only be removed by breaking the flask. Break up the small lumps by powdering in a mortar, and boil them for 10 minutes with two 400 ml. 

As a general rule flasks and similar vessels should be heated in an air bath (compare Fig. II, 5, 3). A glycerol bath may be employed for temperatures up to 140° the glycerol is subsequently removed from the outside of the vessel by washing with water. Medicinal liquid paraffin may be used for temperatures up to about 220° hard hydrogenated cotton seed oil, Silicone fluids or fusible metal may be employed when higher temperatures are required. Small test-tubes and centrifuge tubes... 

Methylnaphthalene. This preparation illustrates the general procedure for catalytic dehydrogenation. The apparatus used is shown in Fig. 6.1. Heat a mixture of 3.2 g (0.02 mol) of the above hydroaromatic compound with 0.3 g of palladised charcoal (Section 4.2.54, p. 452) at 250-270 °C in a slow current of dry carbon dioxide in a Silicone oil or fusible metal bath for 3 hours (1). Cool, dissolve the residue in ether and filter off the catalyst. Wash the extract with dilute aqueous sodium hydroxide and dry it over anhydrous sodium sulphate. Remove the ether and distil the residual oil under reduced pressure use a small-scale distillation apparatus (cf. Fig. 2.111). Collect the 1-methylnaphthalene, b.p. 121-123 °C/20mmHg. The yield is 2.5g (89%). 

Chrysene. Since selenium and selenium compounds are toxic this dehydrogenation and the associated work-up procedure must be carried out in an efficient fume cupboard. Mix 3.5 g (0.015 mol) of hexahydrochrysene with 16 g (0.2 mol) of selenium in a boiling tube and heat in a fusible metal bath at 300 °C for 20 hours (fume cupboard). From time to time, melt the crystalline sublimate which gradually forms so that it runs back into the reaction mixture. Remove the cooled product and grind it in a mortar to a fine powder. [CAUTION (3).] Extract by boiling under reflux for 30 minutes with 200 ml of benzene, filter and reflux the filtered extract over a little clean sodium wire (or thin narrow slices of sodium metal) this treatment removes traces of selenium. Evaporate the benzene solution using a rotary evaporator and crystallise the residue from toluene (about 20 ml per 1 g) (4). Colourless plates with a bluish fluorescence, m.p. 254 °C, are obtained. The yield of chrysene is about 2 g (59%). 

Ignition Temperature, This is usually determined by placing 0 1 g. of the explosive in a smalt test tube, which is then corlud and placed in a fusible metal bath at 100. The temperature is raised 5 per minute until inflammation or explosion occurs. The quantity and rate of heating difler m diffei t countries. 

In BS 2782, Methods I3IC and D [178], test pieces are heat aged and then crushed in a universal testing machine. For method C, test pieces are molded cylinders or cubes with the principal dimensions set to 10 mm for method D, cubes of side 10 mm are cut from the sheet or molding. Duplicate test pieces are heated to I35 C for 17 hours, followed by a further 6 hours at HO C, after which they are immersed in a fusible metal bath at 400 C for 30 minutes and then cooled to ambient temperature in a desiccator. The compression test is applied so as to give failure in 30 15 seconds. 

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