Bentonites are widely used in the industry. The evaluation of their physicochemical properties such as specific surface area, specific pore volume, pore size distribution, surface acidity e.t.c. is necessary for their best performance. Among others, the use of bentonites in catalyst bed and adsorbent production has attracted great attention in recent years, where surface acidity plays a major role in their functions. In this study, the assessment of a reliable and a practical method to determine the surface acidity of bentonite samples was realized. A method based on the adsorption of n-butylamine founded on the determination of the number of surface acid centers by using the Langmuir adsorption isotherms was chosen as a suitable, reliable and practical method to determine the surface acidity of bentonite samples.