Double chamber container for holding and combining, e.g., a lyophilizate and a liquid reconstitution medium, comprising an integral cylindrical body (15) with a closure (20, 60) at each of the two ends (5, 70), an upper movable closure (60) to the side of the reconstitution medium and a lower closure (20) to the side of the lyophilizate, a separating stopper (40) that can be moved in the cylindrical body (15) as a seal between the upper chamber (50) and the lower chamber (30), a bypass (35), arranged below the separating stopper (40), having a length L greater than the height H of the separating stopper (40), wherein at the lower end (5) in the wall of the cylindrical body (15) or in the lower stopper (20) there are provided means (21, 25, 28) that allow connection of the interior of the cylindrical body (15) to the environment during the lyophilization.