Densities of butyltriethylammonium iodide Solutions in methanol, 2-propanone, acetonitrile, and nitrobenzene were measured at 298.15 K. Using published values for the Debye-Huckel limiting slopes A(V), apparent molar volume data were fitted to the Redlich-Rosenfeld-Meyer and the Pitzer equations, allowing the evaluation of partial molar volumes at infinite dilution (V) over bar (0) and deviation parameters B(V). The results show a similarity between the (V) over bar (0) values for the "asymmetrical" quaternary ammonium salt (where the cation has a slightly extended alkyl group) and those for the corresponding "symmetrical" salt (presenting the four alkyl groups identical to the longest of theta). Parameter B(V) is shown to be solvent dependent.