Flask heater

Remove the stopper from receiver 2 and introduce copper shavings. Close the flask with a stopper provided with a dephlegmator and thermometer (see Fig. 20). Wrap the flask in asbestos and put it into an electrical flask heater. What is the boiling point of vanadium oxychloride Transfer the collected liquid into a weighed drawn out test tube. (Wear eye protection, seal the substance in the presence of your instructor ) Weigh the ampoule with the remaining part of the tube. Calculate the yield in per cent. 

Calcination of the americium oxalate to Am02 is done in two stages. The americium oxalate is first heated in a quartz beaker on a flask heater, gently at first to prevent material from being carried out of the beaker by the expulsion of decomposition products of oxalate and then more strongly until the yellow oxalate has entirely blackened. A final calcination of the mixture is done in a platinum dish inside a muffle furnace at 800°C for four hours to insure complete conversion to Am02. 

Preparation of Hydroxylamine Chloride. Dissolve 7 g of sodium hydroxide in 30 ml of water and saturate the solution with sulphur dioxide to an acid reaction, after which pass the stream of gas through the solution for another five minutes (in a fume cupboard ). Add the solution dropwise with continuous stirring to a solution containing 5.5 g of sodium nitrite in 9 ml of water cooled by a mixture of ice and salt. See that the temperature does not rise above 0 °C. Pour the solution into a round-bottomed flask, dilute it to a volume of 150 ml, and heat it to boiling on an electrical flask heater. Perform complete precipitation of the sulphate ions with a solution of barium chloride prepared by dissolving 37 g of barium chloride dihydrate in 45 ml of water. 

I) polyethylene wash bottle (m) single-pan electronic balance with automatic zeroing and digital readout, 100 g 0.001 g capacity (n) electric flask heater (o) solid-state control for electric flask heater (p) stainless steel spatula (q) Keck clamp. 

FIG. 1 Reflux apparatus. A steam bath or electric flask heater Is preferred to a burner. 

When the reaction is complete add 75 mL of water to the hot mixture, heat over a hot electric flask heater and steam distill until the tetrachloroethylene is eliminated and the product separates as an oil or semisolid. Cool the flask to room temperature, decant the supernatant liquid into a separatory funnel, and extract with dichloromethane. Run the extract into the reaction flask and use enough more dichloromethane to dissolve the product use a Pasteur pipette to rinse down material adhering to the adapter. Run the dichloromethane solution of the product into an Erlen-meyer flask through a cone of anhydrous sodium sulfate in a funnel and evaporate the solvent (bp 41°C). The residue is a tan or brown solid (8 g). Cover it with methanol, break up the cake with a flattened stirring rod, and crush the lumps. Cool in ice, collect, and wash the product with methanol. The yield of colorless, or nearly colorless, 5,5,10,10-tetrachloro-tricyclo[7.1.0.0 ]-decane is 3.3 g. This material, mp 174-175°C, consists almost entirely of the cis isomer. Dissolve it in ethyl acetate (15-20 mL) and let the solution stand undisturbed for crystallization at room temperature. The pure cis isomer separates in large, prismatic needles, mp 175-176°C. 

The apparatus must be adequately insulated and the column jacket provided with the requisite heat compensation (section 7.7.3). The use of an automatic column head (section 7.5.3) allows the distillation to be performed with a minimum of attention. In the present case it would be useful to place a contact thermometer, connected to a bell via a relay (section 8.2.2), in the column head. The thermometer would be set to the boiling point of benzene, and when a signal was heard, the initial reflux ratio of 9 would be increased, say, to 20. In the same way it would be progressively raised to the final value of 50. The load may conveniently be regulated by means of a contact manometer actuated by the pressure differential (section 8.4.2). In accordance with the amount of the charge the still pot may be a pilot-plant flask (section 7.6.1) or a round-bottomed flask of 4 to 10 litres capacity, heated by a flask heater (section 7.7.1). 

The method of supplying the electric flask heater with a constant current can be unreliable since it involves frequent checking of the load, especially if there are large differences in the heats of evaporation of the components being distdled. As the pressure drop in a column depends on the vapour velocity (section 4.11), it provides a convenient means for controlling the heater. The method also has the advantage of not being seriously affected by mains fluctuations or by variations in the gas pressure [13]. 

Assembling of the parts should start from the bottom. In the first place it. should be jjossible to remove the still pot without dismantling other components. For tliis purpose flask heaters with a vertical adjustment (Fig. 327) can be used. Plain retort rings do not always give the flask a firm seating. In. some cases the suspension of the flask in a spring cradle (Fig. 414) offers a solution. 

For supporting components that have to be adjusted exactly to a certain level, such as flask heaters, levelling bottles etc., the variable height support due to Mann-chen (Fig. 422) is convenient, as it allows the position to be r ulated to within a millimetre. Ring clamps (Fig. 423) are better than the customary jaw clamps for... 

Kjeldahl digestion flask heaters, with flask supports (100 ml flask size). 

Electric heating Bmi ray electric bunsens suitable (minimum loading 375 watts) or Kjeldahl digestion flask heaters with flask supports (100 ml flask size). 

Kjeldahl digestion flasks 500 cm. Kjeldahl flask heater, 120 watts. Mount flasks in heater at an angle of 30 degrees to the horizontal. 

Lower the flask heater 5 to 10 cm and cool the flask and heater with a gentle stream of air or, preferably, with a stream of carbon dioxide (Note 10). Repressure the contents of the still with dry nitrogen (Note 11) if it is necessary to dismantle the apparatus before it has cooled below 200°C. Carbon dioxide can also be used for repressuring, provided liquid nitrogen traps are not in use. 

The heat density in the flask heaters is approximately equal to 0.5 to 0.6 W/cm. This requires the use of nickel reinforced quartz fabric to ensure a reasonable service life. 

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