The effect of the ionic liquid analogue tetrabutylammonium bromide on the aggregation behaviour of the cationic surfactant dodecyltrimethylammonium bromide in aqueous medium was investigated with volumetric and compressibility measurements over a wide temperature range (293.15–313.15) K. The data obtained were used to obtain density data. Based on the density data obtained, the volumetric properties (apparent molar volumes and partial molar volumes) of the surfactant in unimeric and micellar forms were evaluated and discussed in terms of the respective ionic and dipolar interactions. The data obtained were analysed to determine the effects of (i) temperature and (ii) salt added to the surfactant. The results were also interpreted in terms of the molecular interactions occurring in the binary mixtures of the present study. The addition of tetrabutylammonium bromide has a lowering effect on the CMC values of the surfactant studied in aqueous medium
