The strong decrease of the permittivity of powdered galena with the addition of sodium dodecyl sulphate (SDS) can be linked, as in the case of sodium amyl xanthate, to the chemical nature of its bond with the galena surface: physical adsorption of dodecyl ammonium chloride has no dielectric effect in the range 0.4-100 MHz. Voltammetry and electrokinetic measurements show that the adsorption is independent of potential, contrary to the case of xanthate, and results from an exchange between SDS and anionic species onto the surface, X-ray photoelectron (XPS) and diffuse reflectance by infrared Fourier transform (DRIFT) spectroscopies have been investigated to identify the species responsible for the collection mechanism.