Volumetric properties of aqueous solutions of some cyclohexylsulfamates at 25.0 °C

The densities of aqueous solutions of some salts of cyclohexylsulfamic acid (lithium, potassium, ammonium and tetramethylammonium, synthesized in our laboratory) and of the commercially available sodium and calcium cyclohexylsulfamate, were measured in the concentration range from 0.003 to 1.000 mol kg−1 at a temperature of 25.0 °C. The apparent and partial molar volumes of the solutes studied were determined as a useful tool in elucidating the structural interactions (e.g. ion–ion and ion–solvent) occurring in solution. The apparent molar volumes mainly show small negative deviations from the Debye–Hückelʹs limiting law, though in some cases no deviations were observed. The concentration dependence of the apparent molar volumes was expressed in the form of a polynomial of second degree; the empirical constant Bv which can be used as a direct measure of the ion–ion interactions, equals zero or it is negative for the solutes investigated. Additionally, the partial molar ionic volume of the cyclohexylsulfamate anion was calculated and also the apparent specific volume of the solutes; in general the latter is closely associated with the taste quality. It was found that the values of the apparent specific volumes of the solutes investigated lie on the borderline between the values reported for sweet and bitter substances.