Anti-bumping device

The action of this and other anti-bumping devices e.g., minute carborundum chips) is dependent upon the fact that the transformation of a superheated liquid into the vapour will take place immediately if a vapour phase e.g., any inert gas) is introduced. The effect may be compared with that produced by the introduction of a small quantity of a solid phaM into a supercooled liquid, e.g., of ice into supercooled water. 

Make sure that you add the anti-bumping device before you start heating since uncontrolled boiling may occur immediately. You must allow the liquid to cool back to room temperature and then add the anti-bumping device. 

Add cold water (about 100 mL) and a glass rod as an anti-bumping device to the flask and then heat the mixture on a hot plate until the compound has dissolved completely. Then add more water (about 10 mL), to ensure that precipitation of the solute does not occur during the following stages. 

Heating a test tube - you must wave the test tube in the flame to prevent localized heating, which will cause the liquid to bump out of the tube. Also use an appropriate anti-bumping device and make sure that the tube is not pointing at anyone. 

Introduce 20 to 30 mg of sample into the Wiesenberger flask and add an anti-bumping device (a small piece of platinum is commonly employed) followed by 4 ml of 4N sodium hydroxide (aqueous). Heat for thirty minutes at 150° to 155°, allow to cool somewhat and then immerse the flask in an ice-bath. Run 2 ml of specially-prepared sulphuric acid solution (see below) down the condenser tube, followed by 6 ml of water. Then detach the flask from the condenser using a total of 3 ml of water to rinse down the condenser and the joint surface of the flask. Connect the distillation head to the flask and clamp the condenser at an angle of 45 ° for distillation of the acetic acid. Place 2 ml of water in the funnel above the flask and trap. With the flame of a micro-burner under the flask continue heating until vapour has condensed in the vapour trap... 

In a single-necked round-bottomed flask (2 L), prepare a solution of diethyl malonate (16 g, 0.1 mol) in ethanol (1.0 L), and add 1,5,9-triazanonane (13,1 g, 0.1 mol) and a few antibumping granules. Attach a reflux condenser surmounted by a drying tube and boil the solution under reflux for 5 d. Remove the solvent on a rotary evaporator (care use an anti-splash device to help avoid bumping ) and dissolve the residue in the minimum volume of dichloromethane-methanol (90 10 c. 10 mL). 

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