Distribution data of citric acid between an aqueous solution and a xylene solution of tri-n-octylamine (TOA) were measured in the 283-323 K temperature range. The complexes formed in the organic phase were determined and the equilibrium constants for the formation of these complexes were evaluated. In addition, the apparent thermodynamic data and the mole fraction of each complex present in the organic phase were calculated. When citric acid was extracted with a mixture of TOA and di (2-ethylhexyl) phosphoric acid (D2EHPA), the synergistic and antagonistic effects, depending on either the excess TOA over D2EHPA or the excess D2EHPA over TOA, were also observed and discussed.