Coupled mutual diffusion in aqueous sodium (salicylate + sodium chloride) solutions at 25 °C.

• Binary mutual diffusion coefficients of sodium salicylate solutions at 25 °C. • Ternary mutual diffusion coefficients of aqueous NaSal + NaCl solutions at 25 °C. • Coupled diffusion in aqueous NaSal + NaCl solutions analysed by using Nernst-Planck equations. Taylor dispersion is used to measure the binary mutual diffusion coefficient (D) of aqueous solutions of sodium salicylate (NaSal), a non-steroidal anti-inflammatory drug (NSAID). The D ° value estimated by extrapolation to zero NaSal concentration is used to calculate the limiting mobility of the Sal− ion for comparison with the value determined previously from conductivity data. Salt effects on NSAID diffusion are studied by measuring the ternary mutual diffusion coefficients (D ik) of aqueous NaSal(C 1) + NaCl(C 2) solutions, including results for the diffusion of NaSal in physiological saline solutions with C 2 = 0.15 mol dm−3. As the NaCl:NaSal ratio increases, NaSal diffusion coefficient D 11 changes from the binary diffusion coefficient of aqueous NaSal (a weighted average of the Na+ and Sal− diffusion coefficients) to the tracer diffusion coefficient of the Sal− ion in NaCl solutions. Coupled diffusion in the solutions is analysed by using Nernst-Planck equations to calculate the fluxes of ions migrating in the electric field (diffusion potential) generated by NaSal and NaCl concentration gradients. [ABSTRACT FROM AUTHOR]