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Heating under Reflux
Use of technique
This technique is used for reactions involving volatile liquids.
It ensures that reactants and/or products do not escape while the reaction is in progress.
This is a particular problem since many organic liquids are flammable.
1. Put the reactants into a pear-shaped or round-bottomed flask and add a few anti-
bumping granules to prevent the reaction mixture from boiling and `bumping' out of
Do not stopper the flask doing this would cause pressure
to build up and the glassware could crack or the stopper
could fly out.
2. Attach a condenser vertically to the flask to convert
escaping vapours back to liquids
This will ensure that any volatile liquids return to the
reaction flask and that no products will be lost
Connect to a water supply this maximises the efficiency of the condenser
3. Heat so that the reaction mixture boils gently, using a Bunsen flame or heating
When refluxing correctly, the condensate should reach no more than half way up the
condenser, and the condensed vapour should drip back into the reaction flask