Calculation of liquid junction potentials for equilibrium studies

Abstract

A detalled conslderatlon of the assumptlons underlylng the Henderson equatlon Indicates that, contrary to wldely held vlews, the ciilculatlon of llquld junctlon potentlals vla thls equatlon Is rellable under certaln well-deflned condltlons. I n particular thls Is shown to be true for the constant lonlc strength llquld junctions commonly used In equlllbrlum studles. The valldlty of the potentials calculated from the Henderson equatlon Is demonstrated dlrectly by comparlson of the calculated potentials wlth "experlmental" values and lndlrectly from equlllbrlum constant determlnatlons. The latter lndlcate that accurate thermodynamic lnformatlon can be obtained even In the presence of quite large llquld junctlon potentlals. Some of the llmltatlons and possible applications of the Henderson equatlon approach are brlefly dlscussed.

Ion association and hydration in 3:2 electrolyte solutions by dielectric spectroscopy: Aluminum sulfate

“…As recognized by Xiao et al (2002), extrapolation of such data to infinite dilution depends strongly on the activity coefficient model adopted. In addition, the correction for liquid junction (diffusion) potentials is always problematic (Hefter, 1982) and, again as noted by Xiao et al (2002), their result is higher than those reported by most other researchers.…”

Solubility of L-Cystine in NaCl and Artificial Urine Solutions

“…The liquid junction potentials at this high ionic strength salt bridge are assumed to be negligible in the range 2 < pH < 11 [24]. In all potentiometric measurements, the electrodes were calibrated before and after each experiment.…”

Solid-Solute Phase Equilibria in Aqueous Solutions IX. Thermodynamic Analysis of Solubility Measurements: La(OH)m(CO3)q•rH2O

“…For constant ionic medium junctions, Ej can be deter mined experimentally or, as in the pertinent case, cal culated by an approximate form of the Henderson equation (3) [6,7]; the limiting ionic conductivities Ag were taken from [8]. The e.m.f.…”