The SO2, NO2, and Cl2 generated by combustion will interfere with the measurement. It is excluded that SO2 is removed by reacting with PbSO4 at 600 ℃ to form PbSO4, while Cl2 is removed by metal? Silver is removed by reacting with it to produce AgCl at around 200 ℃, while metallic silver can react with SO2 at temperatures above 500 ℃?? Ag2SO4 is formed by its action and removed, while NO2 is removed by reacting with granular MnO2 to form Mn (NO3) 2.