The extraction of gallium(III) and indium(III) from chloride medium with mixtures of sec-nonylphenoxy acetic acid (CA100) and other organic extractants, including trialkyl amine (N235), N,N-di(1-methyl-heptyl) acetamide (N503), tributyl phosphate (TBP), and trialkyl phosphine oxide (Cyanex923) in n-heptane, has been studied. Synergistic effects are only found when indium(III) is extracted with mixtures of CA100 and N235. The synergistic extraction stoichiometry of indium(III) with CA100 + N235 is studied with the methods of slope analysis and continuous variations. The extracted complex, equilibrium constants, and thermodynamic functions are determined. Moreover, the different extraction behavior of gallium(III) and indium(III) have been applied to discuss the separation of gallium(III) and indium(III). (C) 2010 Elsevier B.V. All rights reserved.