The separation of magnesium isotopes was investigated by chemical ion exchange using a manganese(IV) oxide with elution chromatography. The capacity of the manganese(IV) oxide was 0.5 meq/g. The heavier isotopes of magnesium were concentrated in the manganese(IV) oxide phase, while the lighter isotopes were concentrated in the solution phase. The single stage separation factor was determined according to the method of Glueckauf from the elution curve and isotopic assays.