We monitored these samples by UV-Vis spectrometer and lasted a week. The differences insignificantly change and still exist. After heated at 80 o C with 24 h in oven, the cooled path 2 samples exhibit UV-Vis absorption shoulders in 220-340 nm, especially for the solution with 0.1 mol•kg -1 CoF2, whose spectrum almost exhibits a overlapped shoulder with that of path 1 solution with 0.05 mol•kg -1 CoF2 (Fig. ).