A high purity sodium montmorillonite was obtained by the enrichment of a bentonite (RT) taken from Reşadiye (Tokat / Turkey) region and its hexylamine adsorbed form was prepared by the adsorption of hexylamine (HA) from its aqueous solution. The NaM-HA system was investigated by X- ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), differential thermal analysis (DTA), thermogravimetric analysis (TGA) and the adsorption of nitrogen at 77K techniques. It was determined that the space between the 2:1 layers of NaM of the HA adsorbed form was 0.18 nm larger than that of NaM. It was observed that this increase lead to a 65 % increase in the specific surface area and 120 % increase in the micropore-mesopore volume of NaM.