In this study, fine fractions of bentonites from the Cankiri and Kutahya regions were treated with Na2CO3 and H2SO4. The resulting materials were analysed by X-ray diffraction (XRD), thermogravimetric and differential thermal analyses (TGA. DTA) and infrared (IR) spectroscopy. Surface areas of the samples were also measured. The results showed that structural changes were observed by treatment with Na2CO3 and H2SO4. These changes showed differences depending on exchangeable cations, clay type and the ratio of additives.