Investigations on the Uncertainties of Solubilities of Salts in Solid-Liquid Phase Equilibria of Water–Salt Systems: Taking the Ternary System LiCl–MgCl₂–H₂O as an Example

More and more studies of phase equilibria focus on the accuracy of the solubility data. Consequently, in this work, the uncertainties of Cl– and Mg2+ content in equilibrium solution were calculated in steps by using the Guide to the Expression of Uncertainty in Measurement (GUM) method on the basis of experimental studies. The uncertainty components that may be introduced during the experiment were investigated and calculated, and then, the synthetic standard uncertainty was obtained. The major factors that introduce uncertainty during the experiment are the sampling volume, temperature variations, capacity tolerances of the glassware, etc. According to the uncertainty model established in this work, the uncertainties of the solubilities of salts LiCl and MgCl2 in the ternary system LiCl–MgCl2–H2O were calculated, respectively. The results indicated that the maximum uncertainty of the solubility of LiCl does not exceed ±0.41 and the minimum uncertainty is not less than ±0.17 in mass percent. Moreover, the maximum uncertainty of the solubility of MgCl2 does not exceed ±0.29 in mass percent. As a result, the solubility diagrams with uncertainties of the ternary system LiCl–MgCl2–H2O were plotted in detail. This GUM method can also be widely used to evaluate thermodynamically relevant measurements in solution.