Adsorption of short chain alcohols in decane solutions onto kaolinite has been investigated by Fourier transform infrared spectroscopy (FTIR) for analysis of the alcohol content, The alcohols were methanol, ethanol, 1-propanol, 2-propanol, and 1-butanol, The isotherms have been mathematically modeled by (i) a basic Langmuir equation, and (ii) a two-term Langmuir equation, In both cases, the equations were modified to take into account the self-association of alcohol molecules in the hydrocarbon solution, The methanol isotherm exhibits two plateaus of differing extent, in addition to a strongly increasing isotherm near the solubility limit. It is suggested that this complex isotherm is to be interpreted in terms of monolayer adsorption and condensation in micropores, followed by condensation at the basal surface at higher concentrations, The results further show adsorption isotherms for ethanol, propanol, and butanol in agreement with monolayer adsorption, The calculated area per molecule for the assumed monolayer increases from about 0.15 nm(2) for ethanol to 0.34 nm(2) for butanol, However, 2-propanol gives slightly lower adsorption density than 1-propanol, indicating steric repulsion between the branched chain of the adsorbed molecules, The lower adsorption density of the higher alcohol molecules at the adsorption plateau is possibly caused by steric interactions between the flexible alcohol chains, preventing adsorption onto neighboring sites.