SURFACE AND THERMODYNAMIC PROPERTIES OF SODIUM DODECYL-SULFATE AND SODIUM DODECYL SULFONATE

Determinations of the surface tension of aqueous solutions of sodium d odecyl sulphate and sodium dodecyl sulphonate were made in the presenc e of a neutral salt (NaCl; 0.1 M) at 20 degrees C. On the basis of the se determinations the isotherms and the standard thermodynamic paramet ers of adsorption were determined The equation of state for a monolaye r film of the studied surfactants was also discussed. A linear depende nce was found between log Gamma and log c in the range of low surfacta nt concentrations The limiting value of Pi (A-A(0)) was found to be 1 kT in contrary to the case in which the solutions were made in the abs ence of neutral salt. It has been suggested that there are not only at tractive forces of the Lifshitz-van der Waals type brit also acid-base forces which can affect the Pi parameter.