The reaction mixture consisting of the alkanol, the alkanoic acid and a small amount of concentrated sulfuric acid is heated in a vessel with a water-cooled condenser (Liebig condenser) to prevent loss of volatile material.
After heating, the reaction mixture is then poured into a separating funnel.
Calcium carbonate (CaCO3), or a similar neutralizing agent, is added to the mixture to react with any unreacted acid present in the mixture.
calcium carbonate + acid → water soluble salt + carbon dioxide gas + water
The less dense organic layer floats on top of the more dense aqueous layer.
The stop cock on the separating funnel is opened to allow the more dense aqueous layer to be run off, leaving the less dense organic layer containing the ester in the separating funnel.
The organic layer separated in the separating funnel above contains the ester. This organic layer is distilled to obtain the pure ester. A sharp boiling point is an indication of the purity of the ester.