Organic synthesis. Distillation apparatus used in making an ester. The pear-shaped reaction flask is held by a clamp over gauze on a tripod to ensure even heating from a bunsen burner flame. The flask is connected vertically to a dropping funnel above it, and sideways to a condenser. The chemical in the dropping funnel is added to the reaction flask and the water-cooled condenser is used to trap any gas boiling out of the reaction flask, condensing it in the conical flask. This is distillation, and is often performed to purify an ester. Esters are chemicals used in solvents and perfumes, and are usually made by heating an acid with an alcohol.