Solute–Solute and Solute–Solvent Interactions in the Ternary LiCl + Sucrose + Water System at 298.15 K

In this work, the potentiometric method was used to study the thermodynamic properties of the ternary LiCl + sucrose + water system, where the galvanic cell contained a solid-state chloride-selective electrode and a sodium-selective glass electrode. Measurements have been made for LiCl electrolyte concentrations ranging from 0.0046 up to about 3.800 mol·kg−1 in aqueous sucrose solutions whose molalities varied between mN = 0.1537 and mN = 5.4255 molal (65 wt%). Activity coefficients and standard Gibbs energies of transference of the electrolyte have been determined at 298.15 K. For describing the variation of activity coefficients of LiCl, Pitzer’s equation and a modified form of Pitzer’s equation were used and it was shown that there is a good agreement between them. Evaluation of activity coefficients and the optimized parameters of the two models made it possible to discuss the non-ideality behaviors of the systems in terms of solute–solute and solute–solvent interactions and of their variation according to medium effects. The interactions between electrolyte, sucrose and water were also interpreted in terms of the Gibbs energies of pairwise interaction gEN, for which the positive sign implies repulsive forces between the electrolyte and sucrose. Moreover, the estimated value of the primary hydration number of lithium chloride was within the range of those found by other researchers. Finally the calculated salting constant has confirmed that sucrose may be salted-out by the electrolyte and this fact is consistent with the literature.