Abstract: Magnetic polymer particles prepared by treating compact or porous polymer particles with a solution of iron salts and, if desired, salts of other metals which are capable of forming magnetic ferrites, in which the solution swells or penetrates into the particles. Iron hydroxide and possible other metal hydroxides are precipitated, for instance by raising the pH value, and the particles are optionally heated. In the iron salts used the ratio between di- and trivalent iron is suitably such that magnetic iron oxide is formed directly. It is also possible to use oxidizing or reducing groups or additives to obtain such a ratio. When other metal salts are used in addition to iron salts, the operation is carried out in the same manner. For instance, when Mn.sup.++, Co.sup.++ or Ni.sup.++ salts are used in addition to Fe.sup.++ salts, the divalent iron is oxidized to trivalent so that magnetic ferrite is obtained. The polymer particles which are treated with metal salts preferably contain metal-binding groups.

Abstract: Magnetic polymer particles prepared by treating compact or porous polymer particles with a solution of iron salts and, if desired, salts of other metals which are capable of forming magnetic ferrites, in which the solution swells or penetrates into the particles. Iron hydroxide and other metal hydroxides, if employed, are precipitated, e.g. by raising the pH value, and the particles are optionally heated. In the iron salts used, the ratio between di- and trivalent iron is suitably such that magnetic iron oxide is formed directly. It is also possible to use oxidizing or reducing groups or additives to obtain such a ratio. When other metal salts are used in addition to iron salts, the operation is carried out in the same manner. For instance, when Mn.sup.++, Co.sup.++ or Ni.sup.++ salts are used in addition to Fe.sup.++ salts, the divalent iron is oxidized to trivalent so that magnetic ferrite is obtained. The polymer particles which are treated with metal salts preferably contain metal-binding groups.