In this work, the effects of various organic and inorganic ammonium salts on the liquid-liquid demixing (clouding) behavior of aqueous 1-butanol (BuOH), as a thermo-responsive material, solutions were investigated in the temperature range of 283.15-353.15 K. The inorganic salts used are NH4Cl and NH4Br, and the organic ones are tetramethylammonium bromide (TMAB), tetraethylammonium bromide (TEAB), tetrapropylammonium bromide (TPAB), tetrabutylammonium bromide (TBAB), tetrabutylammonium chloride (TBAC), tetrabutylammonium hydrogen sulfate (TBAH), dodecyltrimethylammonium bromide (DTAB), and cetyltrimethylammonium bromide (CTAB). The inorganic ammonium halides reduced the water-solubility of BuOH and induced the salting-out effect. As the concentration of inorganic ammonium salts increased, the strength of the salting-out effect and the area of the biphasic region increased. However, all the investigated tetraalkylammonium salts had the salting-in effect on BuOH and increased its solubility in water. The extent of the monophasic region and also the intensity of the salting-in effect (co-solvency) enhanced with increasing the concentration of the tetraalkylammonium salts. The effects of the charge density of the salt anion as well as the alkyl chain length of the salt cation, on the immiscibility region of aqueous BuOH solutions, were studied. From the correlation of the measured cloud point data with Setschenow’s relation, the salting effects occurring in the investigated systems were also quantified. Finally, the values of different thermodynamic functions of phase separation were determined, and from which the driving force of clouding at different conditions was discussed.
