Regarding 𝐶 𝐶𝑎,𝐴𝑛ℎ𝑦𝑑𝑟𝑖𝑡𝑒 * an increasing stoichiometric ratio increases the amount of Ca 2+ ions within the solution. Anhydrite is in theory completely soluble in acid. However, as it does not dissolve completely, the leaching reaches the chemical equilibrium, since the solubility of CaCl2 is with 745 g L -1 higher than the measured values . This is dependent on temperature and pH value. However, the temperature is kept constant in all experiments at 𝑇 = 25°𝐶. The measured pH values are listed in Table . A higher stoichiometric ratio implies a shift in the chemical equilibrium and a lower pH. Therefore, it should be possible to express the change in Ca 2+ concentration by measuring the pH, shown in Table . This explains the increase of 𝐶 𝐶𝑎,𝐴𝑛ℎ𝑦𝑑𝑟𝑖𝑡𝑒 * for higher 𝑆𝑡. Contrary to expectations, the percentage of dissolved calcium from particles with higher mass concentrations decreases. However, the total amount of dissolved calcium at higher mass concentrations has increased. For example, at 𝑆𝑡 = 1.0, between 5 and 15 % w/w, 𝐶 𝐶𝑎,𝐴𝑛ℎ𝑦𝑑𝑟𝑖𝑡𝑒 * is greater by a factor of 1.68, while at 15 % w/w, 𝑐 𝐶𝑎,𝑡ℎ𝑒𝑜 𝑚𝑎𝑥 increases by a factor of 3. Thus, the absolute amount of calcium increases while the percentage of calcium decreases. Double the amount of acid and particles does not mean double the amount of dissolved ions. For this reason, it is advantageous to use smaller amounts of particles and acid for the process. shows a decrease with a higher acid content and mass concentration. As the mass concentration increases and the stoichiometric ratio remains constant, the amount of acid added also increases, causing the pH value of the solution to decrease. Compared to anhydrite, the pH values for talc are generally in the same range. Due to its more complex mineral structure, talc has a molar mass of 379.26 g mol -1 , 2.76 times higher than the molar mass of anhydrite at 136.14 g mol -1 . This results in only a third of the molar mass for the same mass concentration. However, according to reaction equation (2), the amount of acid also increases by a factor of 3. The amount of acid used for both minerals is therefore in a similar range and explain the little difference between both alkaline ions. The only noticeable difference is at stoichiometry 0, where no acid is added, which is why only the solubility of the minerals in water has an effect on the pH value. In case of anhydrite, this is in the neutral range of pH 7, while talc has a slightly basic pH value of 8. According to Lin and Cemency, talc has a basic character, which explains this pH value .