𝑚 𝑎𝑐𝑖𝑑,𝑟𝑒𝑞𝑢𝑖𝑟𝑒𝑑 is the theoretical amount of acid required to completely dissolve the alkaline ions according to the chemical reaction (1) and (2). 30 % hydrochloric acid and 96 % sulphuric acid are added to the anhydrite in the ratios 𝑆𝑡 1, 0.5 and 0.2. Citric acid is only added in a stoichiometric ratio of 1, as this is a weaker acid compared to hydrochloric and sulphuric acid.