The adsorption behaviour of safranine-O on specially prepared hydrophilic and hydrophobic surfaces of glass powder was studied at various temperatures (25-55 degrees C). It was seen that the hydrophobic surfaces adsorbed more safranine-O than hydrophilic surfaces at low concentrations while the saturation Value of safranine-O on the hydrophilic surface was greater than that on the hydrophobic surface. This indicated that safranine-O may have been adsorbed by different mechanisms on the two types of surfaces. The different shapes of the adsorption isotherms supported this result. Safranine-O molecules perpendicularly oriented at low concentrations on the hydrophilic surface while adsorption was partly flatwise on the hydrophobic surface. Adsorption of safranine-O can form with Langmuir isotherm at high concentrations for both type of surfaces. Thermodynamic parameters were compared for both surfaces. (C) 1998 Elsevier Science B.V. All rights reserved.