On the Interfacial Potential Differences for the Extraction of Alkaline- Earth Metal Picrates by 18-Crown-6 Ether Derivatives into Nitrobenzene

On an Expression of Extraction Constants without the Interfacial Equilibrium-Potential Differences for the Extraction of Univalent and Divalent Metal Picrates by Crown Ethers into 1,2-Dichloroethane and Nitrobenzene

“…In course of clarifying this expression, some experimentally-determined constants [3] [7], such as K ex± , an individual distribution constant (K D,ML ) of the complex ion ML 2+ into the NB phase and that of AgL + into DCE, were also reproduced by calculation. Here, the AgPic and MPic 2 (M = Ca, Sr & Ba) extraction with L = 18C6 and/or B18C6 [3] [7] were employed as model systems.…”

“…, has caused contradictions on the thermodynamic cycles [3] [7]. Furthermore, such contradictions can cause discrepancies in 0 Δ k φ ′ between experimentally-evaluated values and theoretically-reproduced ones [7].…”

“…However, in spite of the limitation of the same K D,A definition and the same diluents, the thus-determined K D,Pic values have differed from each other. For example, the logK D,Pic values were −0.94 [2] for the PbPic 2 extraction with 18-crown-6 ether (18C6), −1.34 [7] for the SrPic 2 one with benzo-18C6 (B18C6) into NB, −2.4 6 [3] for the AgPic one with benzo-15-crown-5 ether, −1.89 [2] for the PbPic 2 one with 18C6 and −4.3 5 [6] for the CdPic 2 one with 18C6 into DCE. Thus, their values have changed over experimental errors with combinations of MPic z and L.…”

“…In such high-polar diluents, an extracted ion-pair complex, MLPic z , dissociates ML z+ and zPic − [1]- [3] [6]. In introducing these component equilibria in an extraction model, an individual distribution constant (K D,A ) of Pic − (=A − ) into the diluents has been determined extraction-experimentally [1]- [3] [7]. However, in spite of the limitation of the same K D,A definition and the same diluents, the thus-determined K D,Pic values have differed from each other.…”

“…To clarify a reason for such differences, the authors have applied the idea [8] of an interfacial potential difference (∆φ eq ) at extraction equilibrium to an expression of log K D,A , namely On the other hand, from the thermodynamic points of view, these extraction constants are resolved into ( ) ( ) their expressions, because the constants are of homogeneous systems that all species relevant to the reaction are present in the single o phase [3] [7]; namely no interface is involved in these processes. Similarly, the distribution constant of M z+ has been expressed with K D,M (see Equation (3) at 1 z = in the Section 2.1) [3].…”