The adsorption of decyl and octyl Me sulfoxides at the silica/aq. solution interface and the contact angles of sulfoxide solns. on quartz were measured. Effects of temperature and pH on adsorption were studied. The adsorption isotherms are L4 type in C. Giles et al. (1960) classification. The average mol. areas in the saturated adsorption layer are 27-30 A2. The temperature coefficients of adsorption are neg. at low concentration and pos. at high concentration The pH affects the adsorption; the lower the pH, the higher is the adsorption. Contact angle measurements shows that adsorption makes the silica gel surface hydrophobic. The adsorption process consists of 2 stages. In the low concentration range, the interaction is between the solid surface and the sulfoxide group; at high concentration, the hydrophobic effects of adsorbed surfactant mols. and those in solution is significant.

Key words: AQUEOUS SOLUTION, SULFOXIDE, ADSORPTION, SURFACE CHEMISTRY, NON IONIC SURFACTANTS, SILICA GEL