Device for generating gas bubbles in suspensions, which are contained in a tank, having a rotation-symmetric stator and a rotation-symmetric rotor, which is connected to a hollow drive shaft, wherein the stator, the rotor and the hollow drive shaft are arranged concentrically about a vertical axis of rotation of the rotor and the drive shaft, and the rotor executes a rotational movement about the axis of rotation inside the stator, wherein • the rotor has, on its upper end, a plate, which is oriented perpendicular to the axis of rotation and on which vanes (2, 3, 4) are arranged that are oriented perpendicular to this plate and radially to the axis of rotation, wherein the radial extension of the vanes (2, 3, 4) is greatest in the region of the plate, • the stator is constructed as a cylindrical hollow body and the latter projects axially beyond the rotor on its upper side, wherein the casing of the cylindrical hollow body consists of a plurality of strip-shaped, radially oriented baffles and is arranged on a support device, • the support device has a bottom surface, a spacer and a vortex breaker, • the stator is spaced from the bottom surface by the spacer of the vortex breaker, • the top surface, opposite the bottom surface, of the stator has an opening, which is constructed in such a manner that the rotor can be passed through it and the opening is surrounded by a cover ring, which seals the baffles in an axial direction, • at least one opening for the intake of air into the suspension is arranged on the hollow drive shaft of the rotor, below the plate of the rotor, in the region of the vanes (2, 3, 4), characterized in that • the rotor has vanes (2,3,4), which extend from the plate in an axial direction to varying distances, • at least two vanes (3, 4) of the rotor, which are arranged in the circumferential direction of the drive shaft, have a radial distance r to the axis of rotation, a first portion of the baffles of the stator runs at an angle α of 30° to 60°to the axis of rotation and a second portion of the baffles of the stator runs at an angle α' of -30° to -60° to the axis of rotation and the angles α and α' have the same value, and • the baffles of the stator are connected to each other. • the rotor has, on its upper end, a plate, which is oriented perpendicular to the axis of rotation and on which vanes (2, 3, 4) are arranged that are oriented perpendicular to this plate and radially to the axis of rotation, wherein the radial extension of the vanes (2, 3, 4) is greatest in the region of the plate, • the stator is constructed as a cylindrical hollow body and the latter projects axially beyond the rotor on its upper side, wherein the casing of the cylindrical hollow body consists of a plurality of strip-shaped, radially oriented baffles and is arranged on a support device, • the support device has a bottom surface, a spacer and a vortex breaker, • the stator is spaced from the bottom surface by the spacer of the vortex breaker, • the top surface, opposite the bottom surface, of the stator has an opening, which is constructed in such a manner that the rotor can be passed through it and the opening is surrounded by a cover ring, which seals the baffles in an axial direction, • at least one opening for the intake of air into the suspension is arranged on the hollow drive shaft of the rotor, below the plate of the rotor, in the region of the vanes (2, 3, 4), characterized in that • the rotor has vanes (2,3,4), which extend from the plate in an axial direction to varying distances, • at least two vanes (3, 4) of the rotor, which are arranged in the circumferential direction of the drive shaft, have a radial distance r to the axis of rotation, a first portion of the baffles of the stator runs at an angle α of 30° to 60°to the axis of rotation and a second portion of the baffles of the stator runs at an angle α' of -30° to -60° to the axis of rotation and the angles α and α' have the same value, and • the baffles of the stator are connected to each other.