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Abstract--The adsorption of n-octane and water vapor on natural kaolinite was measured. From adsorption isotherms film pressures were determined which were then used to calculate the dispersion and nondispersion components of the kaolinite surface free energy. In addition, thermodesorption of water from the kaolinite surface was determined. These results suggest that physically adsorbed water remained on the kaolinite surface, even at temperatures as great as 125"(2. Therefore, experimentally determined dispersion and nondispersion components appear to relate to the surface precovered with a film of water. These values are: ~gw) = 34.4 mJ/m 2 for dispersion interactions and ~gw) = 60.2 mJ/m 2 for nondispersion interactions. Assuming a kaolinite surface precovered with a film of water, which decreased the free energy by the work of spreading, the following components of the energy for the bare surface were calculated: ~s = 67.6 mJ/m 2 and 3'~ = 103.4 mJ/m 2, for dispersion and nondispersion components, respectively. Key Words--Adsorption, Film pressure, Free energy, Kaolinite, n-Octane, Surface, Water.Abstrakt --Zmierzono adsorpcje pary wodnej i n-oktanu na naturalnymkaolinicie. Z uzyskanych izoterm adsorpcji wyznaczono cignienia film6w i nastgpnie skladow~ dyspersyjn~ i niedyspersyjn~ swobodnej energii powierzchniowej kaolinitu. Pr6cz tego, zbadano tak2e termodesorpcj~ wody z powierzchni kaolinitu. Z tych do~wiadczefi wynika, ~e woda zaadsorbowana fizycznie pozostaje na powierzchni kaolinitu nawet do 125~ Dlatego, sugeruje si~, ~e wyznaczona do~wiadczalnie skladowa dyspersyjna i niedyspersyjna dotyczy powierzchni pokrytej filmem wody. Wyznaczone warto~ci wynosz~: ~gw) = 34.4 mJ/m 2 dla oddzialywafi dyspersyjnych i "Y~w) = 60.2 rnJ/m 2 dla oddziatywafi niedyspersyjnych. Przyjmuj0c model, w kt6rym film wody na powierzchni kaolinitu obni~a jego swobodm~ energi~ o pracg rozptywania, wyliczono skfadowe tej energii dla czystej powierzchni kaolinitu. Sk~adowe te wynosz~: ~ = 67.6 rnJ/m 2 i "r~ = 103.4 mJ/m 2.