Osmotic Coefficient of Aqueous Solutions of Cyclohexylsulfamic Acid at the Freezing Point of Solutions

The osmotic coefficient of aqueous solutions of cyclohexylsulfamic acid was determined by freezing point measurements up to the molality 0.65 mol kg–1. The osmotic coefficients were fitted to the Pitzer equation, and ion interaction parameters α1, β (0) and β (1) were evaluated. The mean ion activity coefficient of the solute was calculated, and the nonideal behaviour of the system investigated was characterized by calculation of the excess Gibbs energy of solution, as well as the respective partial molar functions of solute and solvent. The partial molar excess Gibbs energy of the solute is negative, like the excess Gibbs energy of its solution, while the partial molar excess Gibbs energy of the solvent is positive and increases with increasing concentration of the solute. The solvation ability of water was calculated from the difference between the Gibbs energy of solution of water in solution and that of pure water, and found to be positive and small for the solute investigated, throughout the concentration range studied.