1. Different kinds of air are dissolved in different substances. Of course, carbon dioxide can be dissolved in calcium hydroxide, and sulfur dioxide can also be dissolved in calcium hydroxide to produce white precipitate, just as chlorine gas is dissolved in water to produce hydrochloric acid and hypochlorous acid.
2. Impurity is an insoluble substance in its solution, but it is only insoluble in this solution. Adding hydrochloric acid may also dissolve calcium carbonate generated by adding carbon dioxide to the above calcium hydroxide, and dissolve it after adding hydrochloric acid.