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Two-phase emf titrations have been performed for the extraction of hydrochloric acid from aqueous solution containing 1 M NaCl (M=mol dm−3) by trioctylamine (TOA) dissolved in cyclohexane, toluene, benzene, chlorobenzene, nitrobenzene, cyclohexane–benzene mixtures, and benzene–nitrobenzene mixtures. It has been found that the extraction is accompanied with the formation of monomeric trioctylammonium chloride and its successive aggregation from dimer to micell (n-mer) in organic phase: ‾TOA+H++Cl−=‾TOAHCl, Kd; (‾TOAHCl)i−1+‾TOAHCl=(‾TOAHCl)i, \barKi(i=2,3,···,n), where the concentration quotients of successive aggregation, \barKi, satisfy the relation 2 \barK2=3\barK3⁄2=···=n\barKn⁄(n−1). The quotients Kd and \barK2 vary with the total volume fraction of TOA in organic phase, ΨR°, according to equations, In Kd=1nKd°+gΨR° and 1n \barK2=1n\barK2°+h\barΨR°. Diluent effect on the equilibrium constants Kd° and \barK2° are discussed in detail based on the theory of regular solution.

The exchange reactions of dimethyl sulfoxide (DMSO) with UO2(acac)2dmso and UO2(dbm)2dmso (acac=acetylacetonate, dbm=dibenzoylmethanate) have been studied by the NMR method in CD3COCD3 and CD2Cl2. In CD3COCD3, rates of DMSO exchange for these complexes are independent of the free DMSO concentrations. Rate constants (s−1) at 25 °C and activation parameters ΔH\eweq (kJ mol−1) and ΔS\eweq (J K−1 mol−1) are 2.36×102, 45.8±0.8, −46.6±2.9 for UO2(acac)2dmso, and 3.92×102, 44.5±0.4, −46.2±2.1 for UO2(dbm)2dmso, respectively. In CD2Cl2, the exchange rates are dependent on the free DMSO concentration. For UO2(acac)2dmso, rate=(kd+kIKOS[DMSO])[UO2(acac)2dmso]/(1+KOS[DMSO]), where kd(25 °C=1.02×102 s−1, ΔH\eweq=47.9±5.2 kJ mol−1, and ΔS\eweq=−46.6±11.2 J K−1 mol−1, and kI(25 °C)=1.01×103 s−1, ΔH\eweq=35.4±12.4 kJ mol−1, and ΔS\eweq=−69.7±20.5 J K−1 mol−1, and KOS(10 °C)=4.6±2.1 M−1 (M=mol dm−3). For UO2(dbm)2dmso, rate=(k1+k2[DMSO]) [UO2(dbm)2dmso], where k1(25 °C)=1.74×102 s−1, ΔH\eweq=29.6±2.2 kJ mol−1, ΔS\eweq=−104±9 J K−1 mol−1, and k2(25 °C)=1.62×103 M−1 s−1, ΔH\eweq=34.9±0.6 kJ mol−1, and ΔS\eweq=−67.2±2.4 J K−1. The D and I mechanisms are proposed for the DMSO exchange in these complexes.