Vapor pressure osmometry (VPO) was used to investigate the aggregation behavior of dinonylnaphthalene sulfonic acid (HDNNS), 5,8-diethyl-7-hydroxy-6-dodecanone oxime (HL, the active reagent in the commercial metal extractant LIX63), and their mixtures in hexane at 37°C. The results indicate that HDNNS is present as a heptamer in the concentration range of 1.0×10-3-1.5×10-1 mol dm-3. In the case of the hydroxyoxime, the aggregation yields a mixture of monomers, dimers and trimers for the reagent range of 1.25×10-3-1.0×10-1 mol dm-3. In a hexane solution containing 1.O×10-2 mol dm-3 HL and variable concentrations of HDNNS, the VPO data suggest that HDNNS reversed micelles solubilize the hydroxyoxime to give mixed reversed micelles, which may be represented as (HDNNS)7·sHL, where 7 ≥ s ≥ 0.6 for 2×10-3 mol dm-3 ≤ [HDNNS]T ≤ 1.5×10-1 mol dm-3.
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