Extraction equilibria of citric acid from aqueous solutions with trioctylamine in isodecanol/n-paraffins mixtures, were studied as a function of acid, amine and isodecanol concentrations at 25 degrees C. The equilibrium data were interpreted by "chemical modeling" approach in which existence of (1,1) and (1,2) acid-amine complexes in the organic phase, were assumed. The corresponding equilibrium constants, which represent the experimental results the best, were determined. Simpler mathematical model which refer to modified Langmuir isotherm, was also used for interpretation of the equilibrium data. Extraction constants and overall acid stoichiometric coefficient, which represent the experimental results the best, were determined. This mathematical form could be suitable in the analysis and design of the process in dynamic conditions.