Separation of viscosity B coefficients into ionic contributions. Part 4.—Extrapolation methods using tetra-alkylammonium bromides in dimethyl sulphoxide and hexamethylphosphoric triamide

Abstract

Viscosity B coefficients of the Jones–Dole equation have been determined with a high degree of precision for Pr₄NBr, Bu₄NBr, Pe₄NBr, Hex₄NBr and Hept₄NBr in dimethyl sulphoxide and hexamethylphosphoric triamide at 25 and 35 °C. The B coefficients were plotted as functions of the van der Waals volumes, Stokes radii and formula weights of the cations, and the linear portions of the graphs were extrapolated to the zero value of each property tested. The intercepts thus obtained are discussed and compared with the ionic B(Br^–) values reported previously using Bu₄NBu₄B and Ph₄PPh₄B as reference salts. The reference-salt method is considered to give the best division into ionic contributions.