During the war years the techniques for electromagnetic separation of radioactive nuclides have made great progress. Ever since then further improvements have been accomplished to separate stable nuclides and in more recent years special attention has been given to the problem of separating radioactive nuclides, especially in con nection with spallation and high energy fission studies. This poses slightly different problems, as the amounts of radioactive material may be very small indeed, highly diluted and the whole separation procedure has often to be a very rapid one, as some of the...