Thermodynamics of complexation of aqueous 18-crown-6 with barium ion: apparent molar volumes and apparent molar heat capacities of aqueous (18-crown-6 + barium nitrate) at temperatures (278.15 to 393.15) K, at molalities (0.02 to 0.33) mol · kg−1,

We have measured the densities at T = (278.15 to 368.15) K and heat capacities at T = (278.15 to 393.15) K of aqueous solutions of {18-crown-6 + Ba(NO3)2} at molalities m = (0.02 to 0.33) mol · kg−1 and at the pressure 0.35 MPa. We have applied Young's rule and have accounted for chemical speciation and relaxation effects to resolve Vϕ and Cp,ϕ to include contributions of the 18-crown-6-Ba2+(aq) complex in the mixture. We have also calculated estimates of the change in volume ΔrVm, the change in heat capacity ΔrCp,m, the change in enthalpy ΔrHm, and the equilibrium quotient lg Q for formation of the complex at T = (278.15 to 393.15) K and m = (0 to 0.33) mol · kg−1 in the mixture.