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

Abstract

An idea on interfacial equilibrium-potential differences (∆φeq) which are generated for the extraction of univalent metal picrate (MPic) and divalent ones (MPic2) by crown ethers (L) into high-polar diluents was improved. These potentials were clarified with some experimental extractiondata reported before on the M = Ag(I), Ca(II), Sr(II) and Ba(II) extraction with 18-crown-6 ether (18C6) and benzo-18C6 into 1,2-dichloroethane (DCE) and nitrobenzene (NB). Consequently, it was demonstrated that the ∆φeq values from the extraction-experimentally obtained logKD,Pic ones are in agreement with or close to those calculated from charge balance equations in many cases, where the symbol, KD,Pic, denotes an individual distribution constant of Pic − into the DCE or NB phase. Also, it was experimentally shown that extraction constants based on the overall extraction equilibria do not virtually contain the ∆φeq terms in their functional expressions.

Silver(I) Extraction with Benzo-18-Crown-6 Ether from Water into 1,2-Dichloroethane: Analyses on Ionic Strength of the Phases and their Equilibrium Potentials

“…= logK ex± + log(y ML,org y −,org ) − log(y + y − ) (6) where the subscript "ML" means the complex ion ML + . Rearranging this equation, we can immediately obtain log…”

“…Presences of equilibrium potential differences (∆φ eq ) between aqueous and diluent solutions have been recently reported for the extraction of some M + or M 2+ with L [5][6][7]. This symbol ∆φ eq was defined…”

“…In many extraction experiments, extraction constants for L have been determined so far [1][2][3][4][5][6][7][8]. For example, the two representative constants, K ex and K ex± , for the extraction of a univalent metal salt (M I A) by L have been defined as [MLA] [A − ], respectively.…”

Solvent Extraction of Cadmium Picrate by 18-Crown-6 Ether into Several Less-polar Diluents and Nitrobenzene: Re-evaluation of the Corresponding Overall Extraction Systems

“…According to our previous papers [3,18], a difference between log K D,Pic S and log K D,Pic for the NB system shows the presence of an interfacial potential difference,∆φ eq , at extraction equilibrium. From the relation [1,3,18] …”

“…Applying Equiation (6) to Equation (7) and the term in Equation (8) respectively [18,23]. The symbol ∆φ j 0 ′ denotes the standard formal potential for the species j {= Cd(II), CdL(II), CdLPic(I), Pic(−I), H(I), and HL(I)}.…”