Batchwise measurement of distribution coefficients of earth alkaline metals, on LERHO, lead rhodizonate supported on charcoal, were studied. The adsorption appears to be related to solubility of barium and lead rhodizonates. Preliminary column experiments were carried out as well to check that LERHO is suitable for achieve the preconcentration of radium from extremely diluted solutions. The overall behavior was studied in order to apply it to radiochemical separations.