Cobalt ion in a flowing solution was adsorbed onto the oxine-impregnated activated charcoal in a column. The initial rate of adsorption, K. Am, is influenced by either the flow rate or the ion concentration of a feed solution. The rate increases with a decrease in the concentration of the ion. However, with a solution of <0.06 μg.ml-1 of the ion, the adsorption rate tends to be constant at 0.90 ± 0.06 min-1. A relation between feed application time and column depth (bed depth/service time) has been determined that qualitatively agrees with that obtained from a theoretical calculation. Feed application time for different concentrations and flow rates of feed solutions can be predicted by the bed depth/ service time relation with a limited accuracy.