A Glass Condenser is a piece of laboratory glassware used for cooling hot vapors or liquids. It includes a large glass tube with a small glass tube running the entire length of the condenser. The hot liquid passes through the small tube and condenses in it. In the glass condenser, the ends of the inner small glass tube are usually fitted with ground glass joints that enable it to be fixed with other glassware. The outer glass tube contains two hose connections, and a coolant. During reflux � a technique in the condensation process by which the condensate return to the point of origination - the upper end is left exposed to the atmosphere to prevent the entry of water or oxygen.