COMPUTER CALCULATION OF LIQUID-JUNCTION POTENTIALS .1. CONCENTRATION PROFILES AT JUNCTIONS WITH CONCENTRATED KCL

A numerical method has been used to simulate the junction Z (0.001-6 M) ∥ KCl (4 M), where Z is (a) HCl or an alkali halide with an ion in common with KCl or (b) CaCl2, LaCl3, or K2SO4. By applying diffusion equations to this simulation the ionic concentration profiles have been determined. The diffusion equations used in the calculations of concentration profiles were those arising from irreversible thermodynamics and contain activity coefficients and cross-diffusional terms. The results of the simulation indicate that the concentration profiles at these junctions are better approximated by the limiting case where each component diffuses independently rather than by the continuous-mixture assumption. © 1990.