Analytical Sciences

Abstract − Analytical Sciences, 27(9), 913 (2011).

Extraction of Some Univalent Salts into 1,2-Dichloroethane and Nitrobenzene: Analysis of Overall Extraction Equilibrium Based on Elucidating Ion-pair Formation and Evaluation of Standard Potentials for Ion Transfers at the Interfaces between Their Diluents and Water
Yoshihiro KUDO,* Kyohei HARASHIMA,** Kenichiro HIYOSHI,** Jun TAKAGI,** Shoichi KATSUTA,* and Yasuyuki TAKEDA*
*Graduate School of Science, Chiba University, Chiba 263-8522, Japan
**Department of Chemistry, Faculty of Science, Chiba University, Chiba 263-8522, Japan
Sodium permanganate, sodium picrate (NaPic), Bu4NPic, Me4NPic, and Et4NPic were extracted at an ionic strength of 2 × 10−5 to 0.08 mol dm−3 and 25°C from water (w)-phases into the organic (o)-ones, 1,2-dichloroethane (DCE) and nitrobenzene (NB). Thereby, apparent distribution constants (KD,±) of the anions (A) or the cations (M+) and ion-pair formation ones (KMAorg) of the univalent salts (MA) in the o-phases were determined at 25°C, where KD,± = ([A]o[M+]o/[A][M+])1/2 = (KD,AKD,M)1/2 and KMAorg = [MA]o/[M+]o[A]o. Also, the Kex and KD,MA values with A = Pic, MnO4 were estimated from the relations Kex (= [MA]o/[M+][A]) = KMAorg(KD,±)2 and = KMAKD,MA, respectively. Standard potentials (Δφtr0) for ion transfers at the w/DCE and w/NB interfaces were evaluated from the log KD,A or log KD,M values by assuming the relations KD,Pic = KD,Et4N and = KD,Me4N, respectively. The thus-obtained Δφtr0 values, especially for the w/DCE system, were in good agreement with the values based on the extra-thermodynamic assumption for Ph4As+ and BPh4 transfers at the interfaces. In the present extraction systems, the ion-pair formation of MA in the w- and o-phases was less effective in the determination of their distribution constants into the two o-phases.