## 4 Conclusions  
From the experiments performed, the following picture emerges. \begin{table}
\begin{tabular}{l c c c c c c c c} \hline
**Temperature (K):** & **90** & **110** & **130** & **150** & **170** & **190** & **210** & **230** & **250** \\ \hline \(f\)**-factors: (ferrate(VI), \(\Theta_{\text{D}}\) = 287 K),** & 0.832 & 0.811 & 0.788 & 0.766 & 0.743 & 0.721 & 0.699 & 0.678 & 0.657 \\
**Exp. 8** & & & & & & & & & \\ \hline \(f\)**-factors: (ferrate(VI), \(\Theta_{\text{D}}\) = 252 K),** & 0.792 & 0.761 & 0.729 & 0.698 & 0.667 & 0.636 & 0.607 & 0.579 & 0.552 \\
**average of 7 experiments** & & & & & & & & & \\ \hline \(f\)**-factors: (Fe\({}^{\text{III}}\)(1), \(\Theta_{\text{D}}\) = 300 K),** & 0.843 & 0.823 & 0.803 & 0.782 & 0.761 & 0.740 & 0.720 & 0.700 & 0.680 \\ Exp. 8 & & & & & & & & & \\ \hline \end{tabular}
\end{table} 
Table 4: Mössbauer–Lamb factors (\(f\)-factors) calculated for some selected temperatures for ferrate(VI) according to Equation (2), based on \(\Theta_{\text{D}}\) = 287(20) K from Experiment 8 as well as from an average of 7 experiments (Experiments 1, 2, 3, 5, 6, 7, and 8; Exp. 4 is excluded due to only four measured temperature points), based on \(\Theta_{\text{D}}\) = 252(14) K, and for Fe\({}^{\text{III}}\)(1) based on \(\Theta_{\text{D}}\) = 300(60) K from Experiment 8. Figure 11: Mössbauer spectrum of a ferrate(VI) sample, recorded at 90 K, containing the single Fe\({}^{\text{III}}\)(1) degradation product in a large quantity. Figure 10: Debye fits for ferrate(VI) (**left**) and Fe\({}^{\text{III}}\)(1) (**right**) observed in Experiment 8. The calculated Debye temperatures are 287(20) K and 300(63) K for ferrate(VI) and Fe\({}^{\text{III}}\)(1), respectively. We have confirmed that, out of the three different degradation products observed earlier in electrochemically produced potassium ferrite(VI), Fe\({}^{\text{III}}\)(1) and Fe\({}^{\text{III}}\)(2) form reproducibly, although rather unpredictably, in a particular synthesis. Fe\({}^{\text{III}}\)(3) was not observed in our present study. The assignments of these species are strongly supported by the following facts:  
1. Fe\({}^{\text{III}}\)(1) can form in a large quantity as a single degradation product. 2. The experimental conditions during the synthesis provided a very high hydroxide concentration. Fe\({}^{\text{III}}\)(3) is a hexahydroxo complex of iron(III), [Fe(OH)\({}_{6}\)]\({}^{3-}\), that forms as a primary product in amorphous phase at extremely high OH\({}^{-}\)-concentrations, in practically saturated NaOH or KOH. It must be a short-lived species under crystallization conditions or a decrease in pH. At extremely high pH, this species converts into Fe\({}^{\text{III}}\)(1); this phase most probably is the potassium salt K\({}_{3}\)[Fe(OH)\({}_{6}\)]. The small quadrupole splitting observed in its Mossbauer spectrum (\(\Delta\) = 0.26 mm/s) must be a lattice contribution in this crystalline phase. This phase can be considered as characteristic of the electrochemical synthesis because of the extremely high pH maintained in the anode cell. A decrease in the pH (by dilution with water or contact with CO\({}_{2}\)) results in a transformation into Fe\({}^{\text{III}}\)(2), the most common degradation product of potassium ferrite(VI) in general. We should emphasize here that the actual experimental conditions and the possibly fast transformations of these species into each other make it almost unpredictable which degradation product would actually appear in the synthesized ferrite product. It is fairly logical to expect Fe\({}^{\text{III}}\)(1) to be the most abundant in electrochemical synthesis because a high pH is maintained in the wet product, and the samples are sealed, thereby keeping moisture and CO\({}_{2}\) off the ferrite(VI). We found that Fe\({}^{\text{III}}\)(2) is a common degradation product in dry potassium ferrite(VI) exposed to humid environments and in ferrite(VI) produced by anodic oxidation. On the basis of a literature comparison, it is iron(III) hydroxide, Fe(OH)\({}_{3}\).