Article pubs.acs.org/jced
Isopiestic Studies on Rare Earth Chloride Quaternary System (H2O + LaCl3 + PrCl3 + NdCl3) and Ternary Subsystems Mei He* and Hui-Zhu Long Department of Applied Chemistry, Shenyang University of Chemical Technology, Shenyang 110142, P.R. China ABSTRACT: Isopiestic measurements have been carried out for the quaternary system H2O + LaCl3 + PrCl3 + NdCl3 and its ternary subsystems H2O + LaCl3 + PrCl3, H2O + LaCl3 + NdCl3, and H2O + PrCl3 + NdCl3 at 298.15 K. The results are well represented by the partial ideal solution model and the modified Pitzer ion-interaction model extending to C(3) over full concentration range.
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INTRODUCTION
EQUATIONS The simple modified Pitzer ion-interaction model for the osmotic coefficient (ϕ) and activity coefficient (γ) of aqueous rare earth chlorides (H2O + MX) and their mixtures (H2O + MX + NX + ...) may be given by8
For the highly soluble and unsymmetrical electrolytes, particularly for rare earth chlorides, nitrites, and perchlorates, various modifications of the Pitzer ion-interaction model1 cannot fit the precise isopiestic measurements of Spedding et al. and Rard et al.2−7 very well; however, our simple modified Pitzer ion-interaction model with a C(3) parameter8 can quantitatively represent these literature isopiestic2−7 measurements up to the maximum concentrations available. For mixed rare earth nitrate ternary and quaternary systems,9−12 the simple modified Pitzer ion-interaction model can also quantitatively represent the experimental measurements to very high concentrations. On the other hand, on the basis of the Zdanovskii−Stokes− Robinson rule,13−15 Wang et al.16−20 have presented a partial ideal solution model for every kind of multicomponent systems A+B+C+...+Z related to their binary subsystems A+B, A+C, ..., A+Z at constant activity of the common component A, which can be derived from a modified quasi-lattice treatment. A quantitative verification has been made for organic mixtures, molten salt mixtures, alloys, aqueous and nonaqueous electrolyte and nonelectrolyte solutions. We9−12 have recently reported that the isopiestic measurements for the aqueous rare earth nitrate quaternary systems and their ternary subsystems follow the partial ideal solution model. However, similar information for rare earth chloride quaternary system is lacking. Therefore, it is interesting to make isopiestic measurements for rare earth chloride quaternary system H2O + LaCl3 + PrCl3 + NdCl3 and its ternary subsystems, H2O + LaCl3 + PrCl3, H2O + LaCl3 + NdCl3, and H2O + PrCl3 + NdCl3, to compare the results with the partial ideal solution model and the simple modified Pitzer ion-interaction model. © XXXX American Chemical Society
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+
∑ mcmX (BcXϕ
+ ZCcX ) +
∑∑
c
mc mc ′
c
