## 3 Results and Discussion
The only hint to judge if there is any difference in the Debye temperature for ferrate(VI) and FeIII(2) is Figure 4, where the decrease in the normalized area is steeper for FeIII(2) than for ferrate(VI). According to Equation (3), this means higher \(\Theta_{\rm D}\) for FeIII(2). Since this is based on four measurements, and from the eight experiments we performed a fairly complicated picture emerged for FeIII(2), and FeIII(2) is not the most typical iron(III) degradation product in the electrochemical synthesis of ferrate(VI), we did not pursue measuring an accurate Debye temperature for FeIII(2). At this point, it is worthwhile discussing the identity of the species FeIII(2). As was mentioned earlier, FeIII(2) is a typical degradation product found in potassium ferrate(VI) synthesized by hypochlorite oxidation or by other means, obtaining dry K\({}_{2}\)FeO\({}_{4}\). In humid air, this species forms as far as it may be deduced from its Mossbauer parameters. However, only the isomer shift and the quadrupole splitting (the latter with some variation in the vicinity of 0.7 mm/s) are not enough for perfect assignment of the Mossbauer doublet to one particular species because of the substantial overlap of these parameters for oxygen-coordinated iron(III). In our cases, the magnetic splitting can give more of a hint. Unfortunately, due to the superparamagnetism, it is not always observed. However, where this showed up in our present experiments, the 90 K value was stable, B=42.6 T, and the quadrupole shift was very close to zero. This is the same magnetic field and quadrupole shift we found in our previous work [17] and we attributed this to a new species (different from FeIII(2), denoted as FeIII(4), similar to lepidocroite). Degradation of the solid potassium ferrate was previously studied in humid air [28], and the same doublet was found with \(\delta_{\rm Fe}\) = 0.34-0.39 mm/s and \(\Delta\) = 0.61-0.68 mm/s at room temperature. This species was found to be magnetic below 50 K, a temperature considered as the blocking temperature of a superparamagnetic system. The magnetic field of this component below 50 K is somewhat higher than ours at 90 K by visual inspection (no data given), which is in agreement with the expected temperature variation in the internal magnetic field. On the basis of thermal measurements (temperature-dependent loss of water), it was concluded that this is iron(III)-hydroxide, Fe(OH)\({}_{3}\). It was checked by SEM that the particle size of this phase was extremely small, explaining the superparamagnetic behavior well below 90 K.  
On the basis of this comparison and the variable superparamagnetic behavior in our experiments, we can suggest that our FeIII(2) species and also FeIII(4) [17] are both Fe(OH)\({}_{3}\). The emerging sextet component in aged samples of electrochemically produced ferrate samples [17] is due to crystal growth of Fe(OH)\({}_{3}\) and not to a transformation to another new phase. Let us finally note that in both cases a doublet with well-defined quadrupole splitting transforms into a sextet with practically zero quadrupole shift. It is possible if, in the magnetic phase, the angle between the principal axis of the EFG tensor and the direction of the magnetic field is the magic angle, 54.7 degrees [43]. This similarity strengthens the correspondence between the iron(III) degradation products of potassium ferrate(VI) formed in humid air and in wet potassium ferrite(VI) produced by anodic oxidation. As was mentioned, the previous experiment was conducted on a sample aged after opening its plastic bag. The fresh sample contained the most abundant degradation product, FeIII(1) (Experiment 6), found by us in electrochemically produced ferrate(VI). The Mossbauer measurements were conducted in a wide velocity range in order to notice the presence of any magnetically split components.