Isothermal transport properties in solutions of symmetrical tetra-alkylammonium bromides

Abstract

Density, molar conductance, transference number, tracer diffusion (cation, anion, water) and mutual diffusion data are reported for aqueous solutions of the following symmetrical tetra-alkylammonium halides at 25 °C up to 2 mol kg^–1 concentration: Me₄NBr, Et₄NBr, n-Pr₄NBr and n-Bu₄NBr. These data were used to obtain information on the interactions between pairs of species c, a, w (cation, anion, water) using Hertz's velocity-correlation formalism. Within this formalism the transport coefficients are related to time integrals over velocity cross-correlation functions between the various interaction partners. Results obtained for solutions of tetra-alkylammonium salts differ characteristically from those reported for alkali halides and reflect structural features such as hydrophobic hydration, cation–cation and anion–anion interactions.