The bulk phase solute partition coefficient (K mb ) is an important parameter in the modeling studies of emulsion liquid membrane (ELM) extraction systems, since it gives the ratio of solute concentration in the membrane phase to the solute concentration in the bulk phase at equilibrium. The partitioning of aromatic amines (aniline, p-toluidine, m-toluidine. and 4-chloroaniline) in water-oil-water type ELM systems has been studied experimentally as a function of internal phase volume fraction in the emulsion. Because aqueous aromatic amine solutions (AAASs) are known to photooxidatively decompose under the effect of light, mixing, and aeration which are present in the partitioning experiments conducted in this study, the amount of decrease in the bulk phase amine concentration due to photooxidation needs to be determined. In the partitioning experiments, the equilibrium was reached in the first 5-10 minutes after the emulsion addition to the AAASs. It was found that the photooxidative decomposition of the...