Determination of Ion-Pair Formation Constants for MA⁺ Ions (M = Ca, Sr, Ba, Cu, Cd) with A^- = Picrate Ion in Water by Picric Acid Extraction into Benzene
Pages 71-75
Yoshihiro Kudo, Shinichi Nakajima and Naoki Horiuchi

DOI: http://dx.doi.org/10.6000/1929-5030.2016.05.02.2

Published: 30 May 2016

Abstract: Ion-pair formation constants (K_MA⁰) for MA⁺ = MPic⁺ and MCl⁺ in water were determined at 298 K and ionic strength → 0 by extraction experiments of picric acid (HPic) in the presence of M(II) in the water phase into benzene (Bz) and by potentiometry with a commercial Cl^--selective electrode, respectively. Here, M denotes Ca(II), Sr(II), Ba(II), Cu(II), and Cd(II). In adding Pb(II) data, a relation between K_MA⁰ values was K_MCl⁰<K_MPic⁰ for a given M(II).For CdPic⁺, the K_MA⁰ value (= 136mol^-1 dm³) determined by the HPic extraction was somewhat larger than that (= 108) potentiometrically-determined before with a Cd²⁺-selective electrode, while for CaPic⁺ the former value (= 89) equaled the latter one (= 88) determined before with a Ca²⁺-selective electrode.