Recently I did a distillation. At a certain point an azeotropic mixture of alcohol, water and toluene evaporated and was caught in a beaker with anhydrous potassium carbonate. I had to shake it and then pour it back into the reaction mixture (while filtering out the solid).
Why did I have to catch it in a $\ce{K2CO3}$-mixture?
(The product was diethyladipate)