The invention relates to a device for the automatic opening and closing of reaction vessels. It comprises a holding device for the non-rotatable holding of one or more reaction vessels, a gripper for the gripping of a lid for the reaction vessel, wherein the gripper has gripping jaws to take hold of the lid, and a holding arm with a rotating mechanism for rotatable holding of the gripper. The gripping jaws are arranged in such a way that, when the lid is inserted into the area between the gripping jaws, it is held by the latter through frictional contact, and the gripper has no active operating device for opening and closing the gripping jaws.