Mercury monitor data showing mercury oxidation across a gold catalyst from a typical experiment. The simulated flue gas composition was changed from baseline conditions to high HCl (75 ppm), low HCl (0 ppm) and O₂-free conditions in successive steps. The system was allowed to reach an (apparent) steady state after each change to the simulated flue gas composition before another change was imposed. The oxidation rate was measured during the steady state portion of each time interval. [Hg^T] = total mercury concentration