Abstract

Extraction constants (K_ex± & K_ex) were determined at 298 K for the extraction of sodium picrate (NaPic) by nitrobenzene (NB), 1,2-dichloroethane (DCE) and dichloromethane using 3m-crown-m ethers and their benzo-derivatives (m = 5, 6; abbreviated as L) together with the determination of conditional distribution constants (K_D,Pic) of picrate ion, Pic^-, into these diluents. The K_1,org (= [NaLPic]_org/[NaL⁺]_org[Pic^-]_org) values at the organic (org) phases, such as NB & DCE, were calculated from the relation K_ex/K_ex± = K_1,org. Distribution equilibrium-potential differences (Df_eq) at extraction equilibria were evaluated from the equation Df_eq = -0.05916´(log K_D,Pic - constant) at 298 K. Correlations of the above equilibrium constants, particularly K_ex±, with Df_eq were examined. Furthermore, the standard formal potentials for Na⁺ transfers across the interfaces were briefly evaluated from calculated Df_eq, [Na⁺] and [Pic^-]_org. The above extraction systems were characterized by K_1,org and the complex formation constants of Na⁺ with L in the org phases.

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