“…There are four conventional methods [30] to investigate the structure of extraction complex -equivalent molarity method, chemical analysis method, saturation method, and slope method, among which the slope method is the easiest and the complex structure can be obtained just by the transformation of mathematics formula; therefore, it has been applied extensively [31]. However, our study not only involved simply the extraction process, but a complicated reactive extraction-crystallization process to which it was difficult to apply the slope method.…”