Gluconic acid, C6H12O7, is used for a large number of different industrial applications due to some exceptionally useful properties. However; data about gluconic acid and tri-n-octylamine/diluent system are not avails able in, literature. The aim of this study is to investigate the extraction of gluconic acid from aqueous solutions by tri-n-octylamine dissolved in a variety,of diluents a in wide range of amine concentrations (0.23-1.72 mol/L). Extractin equilibria of gluconic, acid. in the system. solution of tri-n-octylamine in mixtures with 5 various solvents at temperature 258.15 K. have been: measured. Diluting solvents used in this. study are hexane, cyclohexane, toluene, methyl isobutyl ketone (MIBK) and propanol. Using Bizek approach three, acid:amine complexes,. (Acid).(Amine); (Acid).(Amine)(2) and (Acid)(2) (Amine)(3) have been assumed to exist in organic phase. As a result of batch extraction experiments distribution coefficients, loading factors and overall extraction constants were calculated.