The specific adsorption of radiolabeled sulfate ions from perchlorate supporting electrolyte on hematite powder has been investigated. It was demonstrated that a measurable adsorption occurs only at pH values under 5, The adsorption capacity of a given amount of hematite powder tends to a limiting value with decreasing pH. A Langmuir-like adsorption isotherm describes the concentration dependence of the adsorption of sulfate species, It was found that the experimental results are in good agreement with the model suggested recently (Hug, S. J. J. Colloid Interface Sci. 188, 415 (1997)).