General consideration. 19 F NMR spectra of the solutions with identical concentration and component (Zn 2+ //F -//Na + //ClO4 -), but they are prepared by different paths: diluting nearly saturated (at 25 o C) ZnF2 stock solution (~0.12 mol•kg -1 ) with NaClO4 solution (path 1, Fig. ); mixing the NaF stock solution and Zn(ClO4)2 stock solution directly (path 2, Fig. ), are shown in Figs. and. Further details are given in the Supporting Information. Evidently, the 19 F spectra for the solutions with same component prepared by paths 1 and 2 are parallel when the ZnF2 concentration is less than 0.01 mol•kg -1 . However, the spectral difference occurs between both solutions prepared by paths 1 and 2, respectively, when the ZnF2 concentration is up to 0.03 mol•kg -1 . A new sharp peak at ~-130 ppm appears for the solution prepared by path 1. This peak gradually develops as the ZnF2 concentration gradually increases. In contrast, for the solution prepared by path 2, such peak could be observed when the ZnF2 concentration is higher than 0.08 mol•kg -1 and its strength is weaker than those for the solutions with same component prepared by path 1. The observed spectral difference indicates the different F -solution structures in both serial solutions albeit with same component.