The equilibrium molalities In3+ in {In-2(SO4)(3) + Na2SO4 + HDEHMTPCA + n-C8H18 + water} were measured at ionic strength from (0.1 to 2.0) mol (.) kg(-1) containing Na2SO4 as supporting electrolyte in aqueous phase and at constant molality extractant at temperatures from (278.15 to 303.15) K in organic phase. The standard extraction constants K-0 at various temperatures were obtained by methods of extrapolation and polynomial approximation. Thermodynamic quantities for the extraction process were calculated. (C) 2004 Published by Elsevier Ltd.