In comparison between 𝑆𝑡 0.2 and 𝑆𝑡 1.0, the ion yield with 5-fold acid input is therefore only 2.28. Between 𝑆𝑡 0.2 and 𝑆𝑡 0.5 with 2.5-fold acid input, there is an increase of 1.68. The yield to acid input ratio therefore increases with decreasing acid concentration. Noticeable is the solubility product of 1210 mol 3 L -3 at 20°C for anhydrous CaCl2, which leads to a solubility of 745 g L -1 in water . All of the generated CaCl2 should therefore be in solution and solubility is of no importance. Since the Ca 2+ concentration is only 4 g L -1 , there must be a restriction in the chemical reaction. The comparison between inorganic acid with HCl and organic acid with citric acid at 𝑆𝑡 1.0 after 24 h shows that the acid strength of HCl is higher. Accordingly, the ion concentration of citric acid at 981 mg L -1 is 4 times lower for the same input quantity.