k-Value-based ferron assay and its application

Al13 is notable for its promising application in many fields. It has been believed that Al13 could be assayed in term of Al(b) derived from traditional ferron assay. But the inherent relation between Al13 and Al(b) is not clear. Here, the new k-value-based ferron assay using nonlinear least squares analysis is suggested to resolve the ambiguity. The experimental results reveal that the moderate kinetics (k value) around 0.001 s(-1) can be ascribed to Al13. In the short-term aging of freshly neutralized aluminum solutions with OH/Al molar ratio of 2.2, the rapid progress of Al13-like transformation into Al13 can be traced by this method, whereas it may be masked by traditional ferron assay because the metastable intermediates also contribute absorbance to Al(b) fraction. Al(b) can only be regarded as Al13 when Al13 forms completely and becomes the stable specie in the matured solution.