## 4 Results  
### STA Trials  
The objective of testing pure metal chlorides is to gather information on their potential as chlorine-liberating compounds. Figure 4a depicts the mass loss in the STA trials with NaCl and KCl showing full evaporation within the maximum temperature range. The whole amount of sample material was evaporated, indicating no release of chlorine. The highlighted peaks in the DTA signal show the melting points of the chlorides. The assumed behavior that CaCl\({}_{2}\cdot\)6H\({}_{2}\)O reacts to CaCl\({}_{2}\) (no splitting of HCl) was confirmed according to Figure 4b. The theoretical remaining mass when reacting to CaCl\({}_{2}\) was calculated (black horizontal line), which covers precisely with the experimental curve. MgCl\({}_{2}\cdot\)6H\({}_{2}\)O shows the opposite characteristic as the curve covers with the theoretical value for remaining MgO (evaporation of HCl). Both reactions appear to proceed stepwise. Figure 4c depicts the mass curve for the trial with AlCl\({}_{3}\cdot\)6H\({}_{2}\)O, which shows one continuous mass drop to the exact theoretic value of the remaining Al\({}_{2}\)O\({}_{3}\) (full liberation of HCl). For FeCl\({}_{3}\cdot\)6H\({}_{2}\)O, the mass decrease appears in steps, and the final experimentally determined mass is below the theoretical value, which could be attributed to the fact that HCl is not entirely liberated, leading to the partial evaporation of FeCl\({}_{3}\) itself. This is in line with the theoretical evaluations illustrated in Figure 2, where the two curves of reactions with FeCl\({}_{3}\cdot\)6H\({}_{2}\)O (hydrolysis and dehydration) are almost identical at lower temperatures. The data in Figure 4d, which summarize the trial series with In\({}_{2}\)O\({}_{3}\) and all six chlorides, confirm that NaCl and KCl are not suitable for chlorination, as the remaining mass is very close to the calculated values for remaining In\({}_{2}\)O\({}_{3}\) (no chlorination reaction). In a mixture of In\({}_{2}\)O\({}_{3}\) and CaCl\({}_{2}\cdot\)6H\({}_{2}\)O (green line), a first mass decrease, which is associated with the splitting of water, is followed by a stable period up to 1100 \({}^{\circ}\)C and a subsequent mass decrease, which is not completed at the final temperature of 1400 \({}^{\circ}\)C. This can be attributed to a reaction of liquid CaCl\({}_{2}\) with the present indium oxide followed by the evaporation of InCl\({}_{3}\). However, compared to the trials with MgCl\({}_{2}\cdot\)6H\({}_{2}\)O, AlCl\({}_{3}\cdot\)6H\({}_{2}\)O, and FeCl\({}_{3}\cdot\)6H\({}_{2}\)O, the result is poor, as they show almost full chlorination and evaporation (first two mentioned) and a precisely covering curve for iron chloride. \begin{table}
\begin{tabular}{c c c c c c c c} \hline
**Metal** & **Ag [52]** & **Au [53]** & **Bi [54]** & **Cu [55]** & **In [56]** & **Pb [57]** & **Sn [58]** & **Zn [59]** \\ \hline Price [\(\xi\)/kg] & 640 & 50,900 & 6.41 & 8.5 & 390 & 2.04 & 35 & 3.16 \\ \hline \end{tabular}
\end{table} 
Table 2: Market prices of the considered metals as of 29 December 2021. Figure 5a-f confirm the practical effectivity of the three utilized chlorides MgCl2-6H2O, AlCl3-6H2O, and FeCl3-6H2O as chlorination agents for further assessed valuable metal compounds. As depicted, silver chlorination (Figure 5a) proceeds effectively according to the fact that the curves cover with the theoretical remaining mass values for the chlorine carrier oxides. This is in order with the findings in Figure 3a where silver chlorination shows the highest thermodynamic driving force of all elements. As assumed, evaporation starts at elevated temperatures compared to the trials with In2O3 (Figure 4d), ZnO, and PbO (Figure 5b,c). The chlorination of NiO works insufficiently with the actual mass loss being significantly lower than the theoretical calculated values (Figure 5d). In mixtures where indium is present as sulfate, as shown in Figure 5e, it is observed that chlorination seems to be hindered, as the experimental final mass is significantly higher than the calculated values.