Distribution of binary mixtures of citric, acetic and oxalic acid between water and organic solutions of tri-n-octylamine: Part III. Organic solvent chloroform

In this series of publications, the influence of the organic solvent on the liquid–liquid equilibrium in organic/aqueous two-phase systems containing a tertiary amine (tri-n-octylamine) and binary mixtures of carboxylic acids (acetic, oxalic and citric acid) was studied. This third part deals with chloroform as organic solvent while toluene and methylisobutylketone were investigated in the previous parts. Experimental results for the liquid–liquid equilibrium are presented and compared to model predictions. All model parameters were determined from experimental results for pure components and subsystems. When a mixture of citric and oxalic acid is extracted the predicted partitioning of the acids agrees quantitatively with the experimental results. However, when acetic acid is extracted together with citric or oxalic acid experimental distribution ratios are higher than predicted. Quantitative agreement is achieved by assuming the formation of mixed acid complexes (i.e., complexes containing two different acids).