-7In selected experiments, the rare earth fractions (ammo- nium citrate, PH 3.5 a-d) were combined, evaporated to dryness, ashed and redissolved in 0.2N HCl for separation of the individual rare earth elements by secondary elution according to the method of Kimura et al. (1956). Ten ml of a 1:1 suspension - were hb vVLLOOte d T- 5~56 used a8 carrier of Dowex 50 in the H-form (0.2N HCl) were added to the rare earth fraction in a beaker and stirred several times. A ‘mother colwm" of Dowex 50 resin was prepared as described above and converted to the NH,TT*-form by passing NH, citrate, pH 2.5, through the column, until the eluate was at pH 2.5. The rare earth resin suspension was added to the column and ammonium citrate solutions of pH 2.8, 2.9 and 3.1 were passed through until the rare earth fraction started moving down the column as determined by a survey meter, Ammonium citrate solutions of pH 3.1 (120 mi), 3.3 (360 m1), and 3.4 (300 m1) were added to elute the individual rare earth elements. In other selected experiments pH 3.5 and/or 4.1 fractions were reeluted from ion exchange columns containing Dowex 1*, an anionic type resin (supplied in the chloride form), to separate Mn, Co, and Zn from each other according to the method of Kraus and Moore (1953). These fractions were dried, ashed, and redis- solved in 3-5 ml of concentrated HCl and added to a column of 6 mm diameter and 260 mm length. The resin of 100-200 mesh was prepared in the following manner. The resin was twice soaked in distilled water in a beaker and the solution containing the small particles was decanted. * Dow Chemical Co., Midland, Michigan