## 3 Results and Discussion
\begin{table}
\begin{tabular}{c c c c} \hline
**Spectral** & **Isomer Shift at 90 K,** & \
\begin{tabular}{c} **Quadrupole** \\ **Splitting,** \\ **\(\Delta\) **(mm/s)** \\ \end{tabular} &
\begin{tabular}{c} **Suggested Assignment** \\ \end{tabular} \\
**FeIII(1)** & 0.47(3) & 0.26(3) & [Fe(OH)6]3– (crystalline) \\
**FeIII(2)** & 0.43(1) & 0.71(5) & ferrihydrate (?) \\
**FeIII(3)** & 0.437(10) & 0.00(1) & [Fe(OH)6]3– (amorphous) \\ \hline \end{tabular}  
* \(\delta\) relative to \(\alpha\)-iron at room temperature.  
\end{table} 
Table 1: Mössbauer parameters of iron(III) degradation products found in freshly synthesized potassium ferrite(VI) produced by anodic oxidation of metallic iron, with suggested assignments in [17]. The complexity of the case is illustrated in Figure 1 with some selected spectra, where the simultaneous presence of FeIII(1) and FeIII(2) could be identified (Experiment 1). This was the only case with a noticeable combined presence of two degradation products. The evaluation of the iron(III) spectral contribution was performed with fixed quadrupole splittings for the two doublets, as given in Table 1.  
Despite the two different degradation products, the sum of the areas of the iron(III) components is supposed to show a monotonously decreasing line similarly to that found for the ferrate(VI) spectral area (in all experiments). However, an anomalous dependence was found as shown in Figure 1. The curve of the iron(III) species has a positive slope up to about 140 K; thus, it cannot be fitted with the Debye model. In other experiments, we focused on cases where solely the FeIII(1) or the FeIII(2) products could be detected. Although FeIII(2) was much less abundant in our electrochemical syntheses, this is the more typical degradation product of potassium ferrate(VI) either by spontaneous degradation in humid air or in contact with CO2, or in reactions where the ferrate is used as an oxidant. Figure 2 shows sample spectra from a series of experiments where FeIII(2) was the observed degradation product (Experiment 2), but its intensity, again, is not decreasing but is substantially increasing with temperature up to a certain temperature (170 K) as shown in the temperature variation graph in Figure 2. We note that intensity asymmetry was allowed in the spectrum evaluations for the doublet of FeIII(2) because random orientation of the crystallites could not be ensured in our sample preparation technique. This proved to be always small, but it made the line area determinations more accurate. Figure 1: Temperature variation of the normalized areas for ferrate(VI) (purple squares) and for the combination of the iron(III) degradation products FeIII(1) and FeIII(2) (orange dots) with some sample Mössbauer spectra recorded at the indicated temperatures (Experiment 1). Figure 3 shows the results of another series of experiments (Experiment 3) where the increase in the normalized intensity of Fe\({}^{\text{III}}\)(2) is very substantial and lasts in the whole investigated temperature range. This phenomenon proved to be a virtual increase in the intensity of Fe\({}^{\text{III}}\)(2) caused by the narrow velocity range applied in the measurements. Although a visual inspection of the spectra above ca. 120 K shows no irregularity, a closer inspection, especially at 86 K  
Figure 3: Anomalous temperature variation of the spectral areas of species Fe\({}^{\text{III}}\)(2) (orange dots) in Mössbauer spectra recorded in narrow velocity range in Experiments 3. The ferrate(VI) (purple squares) behaves regularly. Figure 2: Temperature variation of the normalized spectral areas for ferrate(VI) (purple squares) and for Fe\({}^{\text{III}}\)(2) (orange dots) with some sample Mössbauer spectra recorded at the indicated temperatures (Experiment 2). (Figure 2), reveals an extra component or components. (In Figure 2, the evaluation already includes an extra component which is a magnetic sextet.)