Volumetric Properties of Aqueous Solutions of Cyclohexylsulfamic Acid

The mean apparent molar volume of cyclohexylsulfamic acid has been determined from the density data of aqueous solutions up to a molality of 0.540 mol⋅kg⁻¹ and at 293.15, 298.15, 303.15, 313.15, and 323.15 K. The mean apparent molar volume of the acid was divided into contributing ionic and molecular apparent molar volumes. The limiting apparent molar volume of the molecular acid amounts to (131.69± 0.02) cm³⋅mol⁻¹ and the limiting apparent molar expansibility to (0.130± 0.003) cm³⋅mol⁻¹⋅K⁻¹ at 298.15 K. From the limiting ionic and molecular apparent molar volumes the limiting volume change of ionization of cyclohexylsulfamic acid was calculated. A value of −7.76 cm³⋅mol⁻¹ was evaluated at 298.15 K. The temperature dependence of the volume change of ionization amounts to −(0.018± 0.009) cm³⋅mol⁻¹⋅K⁻¹. From the density data the coefficient of thermal expansion of the investigated solutions was calculated and from this the mean apparent molar expansibility of cyclohexylsulfamic acid was derived.