Solubilities of ammonia in basic imidazolium ionic liquids

Solubilities of ammonia in four conventional imidazolium ionic liquids: [C_nmim][BF₄] (n = 2, 4, 6, 8) have been measured. Isothermally fixed temperatures are 293.15, 303.15, 313.15, 323.15 and 333.15 K; the pressure is from 0 to 1.0 MPa. High solubilities of ammonia are found, and it is also found that the solubilities of ammonia increase when the length of cations’ alkyl increases (the ILs have the same anion), that is: [C₈mim]⁺ > [C₆mim]⁺ > [C₄mim]⁺ > [C₂mim]⁺. The solubility data have been correlated by the Krichevisky–Kasarnovsky equation, and then Henry's constants and partial molar volumes of NH₃ at infinite dilution are obtained. The thermodynamic properties such as solution enthalpy (Δ_solH), solution Gibbs free energy (Δ_solG), solution entropy (Δ_solS), and solution heat capacity (Δ_solC_p) of these systems are obtained.