The invention relates to a split case for a magnetic coupling, comprising a substantially cylindrical peripheral area (3) and a base (2), wherein the base (2) has, on an inner face (20) of the base directed toward the interior of the split case, a solid cone (4), which is coaxial with respect to a mid-axis (X-X) of the split case, and at least one vortex breaking device (5; 6), which is arranged on the inner face (20) of the base and which projects from the inner side (20) of the base.