Abstract Competitive adsorption of sodium dodecyl sulfate (SDS) and 1-butanol (C 4OH) onto solid Al 2O 3 from aqueous solution of 0.3 M NaCl has been studied. Itis found that the affinity of C 4OH toward the solid surfaceis significantly lower than that of SDS. A bulk concentration of 1 10 renders a surface concentration of 1 1 . A method of separating the area requirements for the components is proposed in analogy to the geometries in the lamellar lyotropic liquid crystalline phase D. Calculation gives 0.39 nm 2 for SDS and 0.30 nm 2 for C 4OH on alumina. The last value is higher than the comparable value from D phases, which may indicate a more horizontal orientation of the adsorbed molecule at the solid surface. These conclusions are, however, based on a complete coverage of the solid surface by the adsorbed species.