The evaporating gases pass through the condenser are cooled, condensed and returned back to the reaction mixture. It is impossible to close the duct, some gases must come out, so as not to pump pressure. To increase the efficiency of the condenser, you can connect cold running water to it, for this it has two outlets. The larger the size of the condenser, the more efficiently it will work. You can take 4-6-8 balls. It is important that the plume of the condenser fits the flask with which it will connect.