Application of the Bjerrum association model to volumes of electrolytes in water and acetonitrile

The Bjerrum association model has been extended to partial and apparent molar volumes. It was tested for electrolytes in water and in acetonitrile using literature or new (n-propylammonium bromide) data to cover systems having association constants between 0 and 10⁵. The association constants and apparent distances of closest approach were obtained from conductivities. The volumes at low concentration can be fitted quantitatively to obtain by extrapolation the standard infinite dilution partial molar volume. Deviations at higher concentrations can be accounted for with a second virial coefficient.